Octal Data Receiver (A3027) Manual

Contents

Description

Retirement Notice: The A3027 is no longer in production. It has been replaced by the Telemetry Control Box (TCB, or A3042).

[22-MAR-21] The Octal Data Receiver (ODR, part number A3027) is a receiver for use with our Subcutaneous Transmitters. The ODR provides eight independent antenna inputs for eight separate receiving antennas. We connect the antennas to the BNC sockets along the back of the enclosure with 50-Ω coaxial cables. The antennas are typically 915-MHz Damped Loop Antennas (A3015A). The ODR also provides four general-purpose digital signals on the front panel that we can configure for particular experiments.

Figure: Octal Data Receiver (A3027D), Front View.

The top row of fifteen LEDs show us transmitter activity. Activity on any channel number with remainder one (1) when divided by sixteen (16) will contribute to the brightness of the channel one (1) activity light. The channel seven (7) activity light is for channel numbers with remainder seven (7) when divided by sixteen (16). The fifteenth channel activity light is blue, for the auxiliary channels, which are those with remainder fifteen (15). The bottom row of eight LEDs tell us the activity on each of the eight antenna inputs. The two green lights indicate power is on. The yellow light is UPLOAD to the LWDAQ Driver. The red light is EMPTY message buffer. These two lights shine together when the LWDAQ is reading out messages as they are received by the ODR. The red switch is hardware RESET. The red light beside it is the RESET indicator. The brown and black switches, with their neighboring orange lamps, are the display function switches, SHOW and HIDE. When we press SHOW, all activity lights turn on. When we press HIDE, the activity lights toggle between being disabled and enabled. We disable the lights to reduce the current consumption of the ODR, which permits us to connect two ODRs to one LWDAQ Driver (A2071E).

Figure: Octal Data Receiver (A3027B) Inside View.

With its eight antennas, the ODR can pick up multiple copies of each transmitter message. The ODR eliminates almost all such duplicates before it stores them to its message buffer. Some duplicates remain. These are eliminated by the Receiver Instrument as soon as it receives the data from the ODR.

Figure: Schematic of SCT System with Octal Data Receiver. In this example, we are recording from thirty mice in six cages within an IVC rack.

The following assembly versions exist. For each, we give the minimum firmware version used to program the circuit's logic chips. The firmware version is available in the last byte of every clock message retrieved from the ODR, as it is with the older A3018. In order to distinguish the Octal Data Receiver (A3027) from the earlier Data Receiver (A3018), we add 30 to the ODR firmware version to create the number in the final byte of the clock message. When the ODR firmware version is 4, the last byte of the clock message will be 34. You can determine the firmware version of your ODR by setting show_messages to 1 in the Neurplayer's configuration panel. When you play back an interval, the firmware version number will be printed.

We describe the firmware versions below. Starting with firmware version nine (9), the A3027 supports communication with Animal Location Trackers (A3032). Starting with firmware version ten (11), the A3027 supports channel numbers 1-222 rather than the original 1-14. The Set Select Register on the A3027 permits the Receiver Instrument to configure the A3027 to record from only one transmitter set or from all of them.

Operation

[22-MAR-21] We control the Octal Data Receiver (ODR) through its LWDAQ interface, and read out the telemetry data through the same interface. The LWDAQ interface is the RJ-45 socket on the back of the ODR enclosure. This RJ-45 socket is not for Ethernet, but for a LWDAQ cable connecting the ODR to the driver. The driver can send sixteen-bit LWDAQ commands to the ODR, and it can read consecutive bytes from the ODR data buffer. The following table gives the ODR's allocation of LWDAQ command bits.

The WAKE bit is reserved for LWDAQ, but serves no function on the ODR. The LB (loop-back) bit sets up the ODR's LWDAQ interface for a measurement of the total propagation delay from the driver to the ODR and back again. We use the loop-back function when looking for problems with the LWDAQ communication. The DTX (data transmit) bit directs the ODR to transmit the next byte from its data buffer when it receives a falling edge on the logic signal from the driver. The RESET bit resets the storage and readout memory addresses and many other internal state machines. It's the bit we write to from the Receiver Instrument to reset the data receiver. The ISTS (instant sample transmission select) bit is available in most, but not all, firmware versions. When we set ISTS, the upper bits R0..R7 represent a seven-bit channel number that the A3027 will match for immediate sample transmission on one of the general-purpose digital outputs.

Antennas

[22-MAR-21] We ship the ODR with eight 2.4-m RG58/U coaxial cables and eight 915-MHz Loop Antennas (A3015C). This antenna will stand upright on the floor of a faraday enclosure or on the surface of a shelf. We can remove its support brackets and strap it to the the structure of an IVC rack. The antennas will almost always be deployed within a Faraday enclosure, and we will carry the antenna signal to the ODR with two coaxial cables and a feedthrough connector.

Figure: Loop Antenna, A3015C, for use with ODR (A3027) Antenna Inputs. This antenna has a stabilizing 3-dB attenuator built in, to stop resonance in the cable between the antenna and the amplifier input.

The purpose of our Faraday enclosures is to isolate the receiving antenna from ambient microwave interference. If we run a coaxial antenna cable out of a Faraday enclosure without connecting its shield to the enclosure wall as it leaves, the cable becomes a conduit for microwave interference to enter the enclosure. Whenver we bring antenna signals out of an enclosure, we connect the antenna cable to a feedthrough in the enclosure wall, and then connect this feedthrough to the ODR with another coaxial cable. We have a variety of coaxial feedthroughs available, see here. Some are connectors mounted in the back walls of our bench-top Faraday enclosures, others are circuit boards we tape to the floor of our canopy enclosures.

The ODR provides eight independent antenna inputs so as to permit robust reception from moving subcutaneous transmitters. In order for the loop antennas to be independent in their reception of radio-frequency waves, we must place them at least 30 cm apart, which is one wavelength of 915 MHz in air. When we arrange antennas in a Faraday enclosure, we should make sure they are at least 5 cm from the conducting walls of the enclosure as well as separated by at least 30 cm. If the antennas are too close to the conducting walls, they stop working. If they are too close to one another, they receive the same signal, and so do not provide the independent reception that permits us to increase overall reception from many animals to ≥98%. The figure below is an example of an effective antenna arrangement.

Figure: An Effective Antenna Arrangement in an FE3A Faraday Enclosure. All antennas are at least 5 cm from the enclosure walls. Try to keep the antennas separated by 30 cm or more. The four coaxial cables should connect to separate antenna inputs on your ODR.

We can increase the operating area of our recording system by connecting multiple antennas to each ODR antenna input. Two antennas connected to the same antenna input will provide additional operating range provided the two antennas are in separate Faraday enclosures, or are least 60 cm apart (two wavelengths of 915 MHz). One way to connect multiple antennas to a single antenna input is with passive power combiners. The ZAPD-1 is a two-way power combiner that will keep the two antennas isolated from one another. The ZB4PD1-2000 allows us to connect four antennas with mutual isolation. Or we can connect two antennas with a BNC T-junction, like this one, and accept that the signal on one antenna will be carried to the other antenna. A BNC T costs about $5 and is readily available, while the two-way isolating combiner is $50 and is a speciality radio-frequency item. We recommend the BNC T as the simplest power combiner.

Figure: Correct and Wrong Way to Use Antenna Combiners. The combiner can be a "BNC T" adaptor.

When combining antenna signals, we must ensure that combined antennas are far apart from one another, or in separate Faraday enclosures. When arranging antennas in an IVC rack, we can use two Eight-to-Four Coaxial Feedthroughs (A3039C) to connect sixteen antennas to an ODR and so provide one antenna on either side of twelve animal cages. We make sure that each pair of antennas connected to each ODR antenna input is a pair that is separated by at least 60 cm in the rack. When arranging sixteen antennas among four Faraday enclosures, we make sure that none of the four antennas in each enclosure share an ODR antenna input with any other antenna in the same Faraday enclosure.

[25-SEP-15] We set up four antennas in our FE4A isolation chamber, one at the center of each wall, on the floor. We place a self-propelled ball with an A3028E attached to it on the floor, so that the ball moves and rotates the transmitter at random about the enclosure floor. We connect the four antennas to an A3027D in various ways. When we connect the antennas in pairs, we make sure that each corner of the enclosure has one antenna from each pair. We measure reception in one-minute periods, repeating the measurement several times for some configurations, in order to account for the dramatic variation in interference power in our office.

Figure: Reception from Moving Transmitter for Various Connections of Four Antennas. Separating lines indicate the passage of an hour or more between series of measurements. Local interference varies by two orders of magnitude on the timescale of one hour.

We see no significant difference between the $50 passive two-way combiner and the $5 BNC-T two-way connector in tests 1-8. The $100 passive four-way combiner, however, gives slightly better performance than a BNC-T four-way combiner. The BNC-T four-way combiner includes two cables as well as three BNC-T connectors.

[01-MAR-16] Reception from a subcutaneous transmitter varies dramatically with the relative orientation of the transmit and receive antennas. The axis of the transmitting antenna is the line bisecting the antenna loop and the transmitter body. When this axis is parallel to the plane containing the receiving loop antenna, we receive ten to a hundred times less power than when the axis is perpendicular to the receiving loop. If we have two antennas available to pick up signals from within one animal cage, we will do better to place the two loops perpendicular to one another. If we have three antennas that are mutually perpendicular, there is no orientation of the transmitter that will place its antenna axis perpendicular to all three receive antennas.

In practice, the reflecting walls of faraday enclosures and isolation chambers rotate the radio waves emitted by our subcutaneous transmitters, so that two antennas with parallel faces, but in different places, will receive the signal from a particular transmitter with a different orientation. Thus, if we keep two parallel antennas 30 cm apart, the chances of the signal received from the transmitter being unfavorably oriented with respect to both antennas is reduce. Nevertheless, we recommend that your antenna arrangement provide perpendicular antennas to make more certain of robust reception.

Local Oscillator

[02-APR-16] The local oscillator (LO), shown in S3027_2, generates a sinusoidal waveform of 866±1 MHz MHz that the A3027 uses to down-shift its antenna signals from 900-930 MHz to 34-64 MHz. The oscillator is based upon that of the A3016SO. We have an ERA-3SM amplifier, U1, whose output is fed back to its input through a 4-way splitter, a 6-dB attenuator, a delay line, and an 866-MHz SAW filter. Thermal noise is amplified by U1. Noise in the pass-band of the SAW filter arrives back at the input and is amplified again. A sustained oscillation develops at a frequency for which the net phase delay around the loop is 360°. The total distance the wave travels around this loop is roughly 134 mm, including the distance traveled through the components. According to our observations, with the ERA-3SM amplifier and a B3563 filter, we should get oscillation at around 865 MHz, and we find we get 866±1 MHz.

The SAW filter we used from 2013-2019 in the A3027A through A3027E is the B3563 with nominal center-frequency 864 MHz. We observed when working with our A3020SO that the B3563 supported oscillation at 865 MHz when combined with the phase shift of a 100-mm delay line and an ERA-3SM amplifier. The delay line is a way of introducing a known phase shift. We found that the phase shift of a SAW filter varies dramatically in its pass-band when we worked with our A3014SO. Thus we can tune our SAW oscillator by picking the correct delay line length.

The A3027 must provide a local oscillator for eight separate mixer. So we split it into four equal parts. One part goes back to the input of U1. One part we take through an attenuator to a BNC socket so we can measure the LO frequency. The other two parts we amplify with U2 and U3 and split into four parts each. The eight LO signals are nominally +6.6 dBm each, which is sufficient to drive the ADE-2ASK mixer used in the A3027 demodulating amplifier. We transport the LO signal with coplanar waveguides. We first used the coplanar waveguide in the Active Antenna Combiner (A3021B). The A3027 circuit board provides four copper layers. To build the waveguides, we clear the second copper layer, which is elsewhere the ground plane, and allow occasional power and low frequency tracks on the third layer. The bottom layer is the ground plane. The top layer is ground plane except where the curving signal traces run through it. The traces are 50-mil wide with a 7-mil gap to the ground plane on either side. The nominal trace impedance is 50 Ω. Phase delay is around 1.8°/mm. The distinctive curving tracks of the waveguides carry the LO power across the circuit board to the eight mixers of the demodulating amplifiers.

The J1 socket provides us with a convenient means to measure the LO power and frequency. In three separate A3027s, we measure +4 dBm and 866 MHz at J1. The four-way splitter (L4) and attenuator (R2) between U1 and J1 introduce a loss of 13 dB, so we believe U1 is producing 17 dBm. The input to L1, the SAW filter, is 4 dBm, which is a above its maximum power rating of 0 dBm. The inputs of U2 and U3 see 10 dBm, and we assume they produce 17 dBm also. Our LO1-LO8 signals for the eight antenna amplifiers will be roughly 11 dBm.

Demodulating Amplifier

[02-APR-16] The Demodulating Amplifier of the A3027E is shown in S3027_1. The circuit is similar to that of the A3017, except that we now use coplanar waveguides with ground planes to carry the RF signals before they are down-shifted. The demodulating amplifier circuit is repeated eight times, for n from 1 to 8, so as to provide eight antenna inputs.

At the intput of the amplifier, we connect an antenna. The antenna's all-frequency signal (AFn) is amplified by Un01, ERA-3SM, which provides ≈20 dB gain from 0.1-3 GHz. The amplified AFn passes through band-pass filter Ln03, B3588, which selects 900-930 MHz. The radio-frequency signal (RFn) output of the filter is amplified by Un02, ERA-3SM, and passes into mixer Ln04, ADE-2ASK, where it is multiplied by local oscillator signal LOn, which is 866±1 MHz. The mixer output is dominated by two components: the RFn signal downshifted by the LO frequency, and the RFn signal upshifted by the LO frequency. These two components occupy frequency ranges 34-64 MHz and 1766-1796 MHz respectively. The mixer output passes through low-pass filter Ln05, which passes frequencies 0-65 MHz, and so extracts the downshifted component of the mixer output, to produce the intermiediate frequency signal (IFn) in the range 34-64 MHz.

We amplify the IFn signal with a limiting amplifier made of three OPA699 op-amps. These op-amps limit their output to lie in the range VLB = 1.8 V to VLT = 3.2 V. We power the IF amplifier with a single +5 V so as to reduce power consumption. We use VCOM = 2.5 V as our signal ground. The VLB, VLT, and VCOM voltages generators are shown here. We couple the IF signal into each amplifier with 100 pF and 1.0 kΩ so as to provide a lower corner frquency of 1.6 MHz. When the corner frequency is below 100 kHz, the IF amplifier and the VLB, VLT, and VCOM generators can together sustain oscillate at a few tens of kilohertz. The limiting amplifier provides a total gain of around 65 dB, with output amplitude limited to 1.4 Vpp. The amplified IFn emerges as IFLn.

The IFLn signal passes through a 100-Ω resistor and a tank circuit made of a 100 nH inductor and a 47-pF capacitor. Depending upon the exact value of the inductor, we may add 10 pF to the capacitor to ensure the resonant frequency of the tank circuit is 930±3 MHz. The tank circuit takes the constant-amplitude, frequency-modulated IFLn signal and gives it an amplitude that increases with frequency from 900-930 MHz (Fn). We pass F into an amplifying demodulator made of diodes and op-amps. The rusult is the demodulated signal (Dn). The plots below show how D varies with frequency of the RF input.

Figure: Demodulated Output (Top, 500 mV/div) versus Frequency for One Antenna Input on the Octal Data Receiver (A3027A). Left −32 dBm sweep, right −80 dBm sweep. Bottom trace is the TUNE input to our Modulating Transmitter (A3014MT) Serial Number 1, see here for calibration. The left vertical line marks 900 MHz and the right is 930 MHz.

We obtained the above traces in the absence of significant local interference. In a city, we can expect a −80 dBm sweep to be overwhelmed by interference penetrating our A3027 enclosure, and expect our −73 dBm trace to look like the one on the right.

Discriminator

[02-APR-16] The output of the demodulator, D, passes through the discriminator filter to become the comparator signal C. The discriminator filter consists of Cn17, Cn18, Cn19, Rn20 and Rn21, as shown S3027_1. The filter combines a low-pass filter of 100 pF and 135 Ω with a high-pass filter of 200 pF and 540 Ω. Its step response is as shown below.

Figure: Step Response of Discriminator.

The discriminator filter extracts signals of average value zero and modulated at approximately 5 MHz from D. The modulation signal generated by reception of a subcutaneous transmitter message consists of transitions from one level every 100 ns or 200 ns. The step response decays slowly enough that 200-ns steps will be preserved adequately for discrimination, but longer HI or LO periods will be attenuated. In particular, the average value of the demodulated signal will be subtracted, so that it is only transitions in D that will be passed to the comparator. Steps shorter than 10 ns will also be attenuated, which reduces transitions caused by noise, and so reduces the bad message rate in the receiver.

The filter output passes into a comparator, and so becomes a sequence of logic levels, Qn. The combination of the discriminator filter and the discriminator comparator are the discriminator. The filter is based upon that of our Data Receiver (A3018D). We have increased the resistors by a factor of ten and reduced the capacitors by a factor of ten so as to increase the network's impedance by a factor of ten while leaving its step response the same.

Robustness of Reception

[02-APR-16] With eight independent antennas, the A3027 is supposed to provide far more opportunities for a transmitter message to be received and decoded. Transmitter messages are received correctly when their power is more than ten times the power of the ambient radio-frequency interference in the 900-930 MHz band. Otherwise, the interference dominates.

[30-AUG-13] We place two A3015B loop antennas beside a piece of letter paper on a table. The antennas are on adjacent sides of the paper. We connect one antenna to our A3027 and move an A3019D around over the paper in our hand at random. Reception is 24% over one minute. If the chance of a message being lost is 75%, the chance of it being lost by two independent antennas is 50%. With two antennas we expect 50% reception. We connect the second antenna and repeat the measurements. Reception is 74%.

[20-SEP-13] We set up three A3015B loop antennas all in a row, separated by 30 cm, with their loops co-axial. Our ambient interference power is −49 dBm as measured by our A3008B spectrometer. We take an A3019D transmitter in hand, with its antenna exposed to air and move it at random in the 30 cm cube between the left and center antennas for one minute. Reception is 100.0%. We disconnect the right-side antenna. Reception drops to 98.2%. We disconnect the left-side antenna. Reception drops to 96.6%. We repeat these three measurements, but holding the transmitter entirely enclosed in our hand, so the antenna is enclosed in human body tissue at least 2 cm deep. We obtain 94.4%, 84.6%, and 53.8%.

Let us suppose that the chance of a message failing to arrive at an antenna is independent for the three antennas. In that case, the chance of losing a message is 3.4% for antenna in air and 46.2% for antenna in hand. We would then expect reception for two antennas to be 99.9% and 78.7% respectively. We see 98.2% and 84.6%. For three antennas we would expect 100.0% and 91.9%. We see 100.0% and 94.4%. It appears that the chance of one antenna missing a message is slightly lower if another antenna is missing the same message at the same time, so an assumption of independence gives us a conservative estimate of the benefit of multiple antennas.

[31-OCT-13] At ION, we set up an Octal Data Receiver and plug in four antennas. We arrange them as if they were on the shelves of an IVC rack, with no enclosure or absorbers around about. We measure reception as if in a cage between them by holding the entire transmitter in our fist and rotating at random for ten seconds, while watching reception in the Receiver Instrument. With one antenna we get 30±10% reception, two give us 60±10%, three gives us 90±5%, and four gives is 97±3%.

[31-DEC-13] The Octal Data Receiver, like the Data Receiver (A3018), requires that transmit clock period of the messages it receives be close to 200 ns, for 5 MBPS. Today we used a batch of A3028s to obtain the following graph of reception efficiency versus transmit clock period. In all cases we ensured that the mark-space ratio was 48-50%.

Figure: Reception versus Transmit Clock Period. Reception is from two-channel transmitters, so we have two graphs, one for the first channels and another for the second channels.

Reception works well for clock periods 195-218 ns, but poorly outside that range.

[10-MAR-14] We set up eight antennas in an IVC rack at ION and measure reception with and without the walls of a radio-frequency isolation chamber around the rack. Without the isolating walls, reception is adequate in the cages well-covered by antennas. With the isolating walls, reception is 100.0% everywhere in the rack. For photograph and more details see Performance of Chamber for IVC Rack.

[08-OCT-14] We set up a 1.2 m × 0.6 m isolation chamber on our concrete basement office floor with a sheet of reflecting steel mesh fabric on top. We attach an A3019D transmitter to a self-propelled ball and allow the ball to move the transmitter at random across the floor of the enclosure. Click on the figure below for a video of the ball in action.

Video: Radio Frequency Isolation Chamber and Self-Propelled Ball with Transmitter.

We record for one minute within the chamber with between 1 and 4 antennas, and with the roof on and off in the case of 4 antennas. The graph below shows how reception varied during a minute under each arrangement.

Figure: Reception During Sixty Seconds for Various Arrangements of Antennas and Roof. For each plot we give the number of active antennas and whether or not the roof is on or off.

The average reception during the one minute is for 4-ON 99.9%, 4-OFF 86.8%, 3-ON 98.8%, 2-ON 96.5%, 1-ON 82.9%, and 4-ON repeated 99.7%. Our intermittent local Ê is particularly powerful. As shown here, the power outside our chamber reaches −45 dBm, while within the chamber we get no more than −70 dBm. We see today that the roof of the isolation chamber is necessary to ensure robust reception, which we define as ≥95%. We need two or more antennas.

[07-JUN-17] We have a ten-minute recording of a transmitter attached to a self-propelled ball rolling around in a box with two receiving antennas in an FE2F enclosure. We obtain the following loss of signal.

Figure: Reception from Transmitter on Self-Propelled Ball in FE2F Enclosure with Two Antennas.

[09-JUN-17] We have 10 of A3028L dual-channel 1024 SPS transmitters, channel numbers in the range 71-94. We turn them all on and place them in water within a faraday enclosure with two antennas connected to an A3027E. The total sample rate is 20 kSPS. We plot reception versus time in one-second intervals for the channels with the best and worst reception.

Figure: Reception from Ten Dual-Channel 1024 SPS Transmitters with Two Antennas. We plot the best and worste channels. Their average reception is 96% and 77% respectively.

Each channel has eighteen others with which it can collide (transmitters don't collide with themselves). We discuss collions in detail here. Each transmission is 7 μs, so the likelyhood of a given sample colliding with another is, on average, 7 μs × 2 × 18 × 1024 ÷ 1E6 = 25%. With one antenna we expect an average 75% reception. We observe an average of 87% with two antennas for all channels combined, and a minimum average of 77% for any one channel.

[25-OCT-23] We have four SCTs in boxes with connectors, each with a different center frequency. We have measured their power output. With attenuators, we can vary the SCT signal power we deliver to a combiner, in which we combine the SCT signal with a constant-frequency interference signal that we adjust to the center frequency of the SCT signal. For SCT signals −47 dBm to −5 dBm we measure the maximum interference power for which we can still obtain 90% SCT reception. We plot the ratio of interference power to signal power. This ratio is our interference tolerance.

Figure: Interference Tolerance of the Octal Data Receiver (A3027E). For four center frequencies, and a range of signal powers, we give the maximum ratio of constant-frequency interference power to signal power for which we obtain 90% reception. (By Nathan Sayer)

The interference tolerance of the ODR is between −10 and −5 dBm for the range of signal powers we are likely to see on a telemetry antenna.

Power Supplies

[25-APR-17] We measure the current consumption of five A3027Es and get 240-243 mA from ±15V and 222-230 mA from +5 V when the circuits are idle. There are no antenna or activity lights illuminated. Given that the power supplies of the LWDAQ Driver (A2071E) are rated at 500 mA at ±15V and 2000 mA at +5V we see that a single LWDAQ driver should, in theory, be able to support two A3027E ODRs. When we press the SHOW button to turn on all the white LEDs, current consumption increases to 330 mA, at which point we cannot connect two A3027s to one LWDAQ Driver (A2071E). If you want to connect two A3027s, press the HIDE button to disable the indicator lights, and current consumption will be reduced.

The A3027 uses only +5 V and +3.3 V power. The +5 V runs the Local Oscillator, the Radio-Frequency Amplifiers, the Intermediate Frequency Amplifiers, and Demodulators for the eight antenna inputs, as well as the white and blue indicator lamps on the front panel. This +5 V we obtain with a CC10-2405SR-E 5-V isolated output DC-DC converter, L10, from the LWDAQ ±15 V power supply. The logic runs off +3.3 V. This voltage we obtain with an LTC3404 buck regulator, U7, with a 10-μH inductor, L9, from the LWDAQ +5 V power supply.

Figure: Current Consumption of the A3027 as Measured by LWDAQ Power Monitors.

The difference between the +15V and −15V current is due to a scaling error in the current measurement made with the LWDAQ power monitors. When we plug a second A3027C into one A2037E driver, the ±15-V power supplies turn off. When the A3027C starts up, it's light flash and it draws a total of 341 mA. This adds to the first A3027C's 255 mA to make almost 600 mA. The LWDAQ ±15-V current limit is 500 mA. With the white indicator lamps turned off, the A3027C to consumes 250 mA from 30 V. The L10 converter is 86% efficient, so it appears that the A3027 is drawing around 1.2 A from its +5-V power supply, which is what we estimate from looking at the typical current consumption of the amplifier and local oscillator components.

Message Control

[27-JAN-17] The A3027 message control consists of a Message Detector, Message Router, and Message Memory. Messages are detected, selected, stored in memory and uploaded to the LWDAQ driver when requested by the data acquisition software.

The Message Detector is U16, a 512-gate programmable logic chip. The outputs of all eight Demodulating Amplifiers are connected to the Message Detector, which provides eight independent message decoding circuits to identify SCT messages in the random sequence of bits generated by noise, interference, and SCT signals in each Demodulating Amplifier. The Message Detector uses a temperature-compensated 32.768 kHz oscillator, U13, to provide a timestamp for message. It eliminates almost all duplicate messages detected by its multiple antennas. For details of how it works, see the P302702Axx.abl and P302702Axx_Decoder.abl files, where xx is the version number. The Message Detector functions use up 90% of the logic available in U15.

The Message Router is U15, another 512-gate programmable logic chip. It reads messages one byte at a time from the Message Detector and stores them in RAM at its storage address. When it receives a data strobe from the LWDAQ Driver, it fetches a byte from RAM at its transmit address. For details of how it works, see the P302701Axx.abl and P302702Axx_Indicator.abl files, where xx is the version number. The Message Router functions use only 30% of the logic available in U15.

Memory

[10-SEP-13] The A302701A layout provides U14, a 512 KByte, 10-ns static RAM. This works fine, and is identical to the memory used by the A3018. The Message Router has three hundred spare logic gates, which is enough to build an eight-bit microprocessor with a hardware multiplier (see ISL Conceptual Design). If we were to implement a microprocessor in the Message Router, we had best provide some non-volatile memory for an operating system. Thus we add a serial FRAM (Ferromagnetic Random Access Memory) in an SOP-8 package to the A302701B layout. The FM25V02 from Cypress provides 32 KBytes of 40-MHz non-volatile RAM.

Digital Input-Output

[02-APR-16] The A3027 provides two bi-directional low-voltage differential logic signals (LVDS) and two bi-directional 3.3-V single-ended logic signals. The S3027_5 schematic shows all four logic signals and their connectors. The LVDS signals are Y1 and Y2. They are available on the front panel of the A3027 on two USBA plugs. These plugs also provide 5-V power for auxiliary circuits. The single-ended signals are X1 and X2. They are available on the front panel on two BNC sockets. There is a 1-kΩ resistor in series with X1 and X2, and diode clamps, to protect the A3027 logic chips from electrostatic discharge and external over-voltages. The A3027 firmware determines the behavior of each signal. We describe the behavior of the inputs and outputs in below.

Firmware Versions

[28-JUN-25] The A3027 firmware version determines the behavior of the inputs and outputs, as well as correcting bugs in the operation of the logic, and adding features such as increasing the range of channel numbers from 0-15 to 0-255. Look in the Receiver Instrument or Neurorecorder Tool for notification of your A3027 firmware version. If you have a firmware version V11 or lower, we recommend you arrange for a firmware update. If you have firmare version V12, read the section below on V12 for an explanation of odd behavior of the activity lights. To re-program your firwmare, see Firmware Reprogramming. For an example of a program that uses the A3027 logic outputs to control other hardware, consider the Slow Pulse Generator.

Firmware V4: The X1 output is Antenna One Detecting. Any time Antenna One receives something that starts to look like an SCT message, X1 goes HI. The photograph below shows X1 when we are receiving perfectly from three transmitters that are not colliding.

Figure: Antenna One Detecting Output on X1. We have a sharp rising edge for X1 on the A3027 circuit board, and a slower rising edge at the end of a 1-m coaxial cable with a 50-pF terminating capacitance.

We use the X1 signal to trigger on SCT transmissions so we can examine signals inside the A3027 and watch the transmit bits as they are amplified and demodulated. The X1 signal is asserted after five synchronizing edges are received from the transmitter. The 6.1 μs detection time is the remaining 31 bits transmitted by these SCTs, at a nominal 200 ns per bit, gives 6.2 μs. The actual bit time varies from one transmitter to the next, which is why there are three falling edge locations in the photograph.

Firmware V5: We configure the A3027 for Immediate Sample Transmission. By transmitting a command through the LWDAQ to the A3027 we select one channel number for immediate transmission as a sixteen-bit serial word on X2. A LWDAQ command is itself a sixteen-bit number. We can send individual commands to the A3027 with the Diagnostic Instrument. The sixteen-bit hexadecimal command 0n02 instructs the A3027 to transmit all samples it receives from channel number n. When the A3027 powers up, the selected channel number is zero, so the A3027 transmits the samples of channel zero, which is the timestamp channel. The transmitted samples start at zero and increase to 65535 at 128 SPS. If we turn on an A3028A dual-channel 512 SPS transmitter using channels 1 and 2, we can select the first channel for immediate transmission with command 0102. If we want to select channel number 141, we must translate 141 into hexadecimal, and enter 8D02. The channel selection will remain in place until we send another command to change its value, or we press the front-panel hardware reset button, or we cycle the power.

The speed with which we can transmit the sixteen-bit serial word is limited by the length of the coaxial cable we use to carry the signal to our external logic, and the terminating capacitance at the end of the cable. The photograph below shows a 333 kHz clock on X2 with a 2.6-m RG58C cable and a 50-pF terminating capacitor.

Figure: Rise Time of X2 with 2.6-m Coaxial Cable and 47 pF Load. The sharp rising edge is X2 on the A3027 circuit board, after the 1k0 series resistor (R21). The longer rising edge is X2 at the far end of the cable.

The flickering in the rising and falling edges are periodic steps in the edges with period 28 ns. Our coaxial cable has propagation delay 4.0 ns/ft and length 2.6 m. The signal takes 10.4 ns to reach the far end of the cable, where it is reflected, and 10.4 ns to come back. When we shorten the cable to 107 cm, the period of the steps drops to 11 ns. The immediate sample transmission proceeds at 4 μs per bit, so as to give plenty of time for the signal at the other end of a 2.6-m cable to settle for each bit. The photograph below shows the transmission of timestamp samples.

Figure: Immediate Sample Transmission on X1 at the End of 2.6-m Cable. Here we show transmission of channel zero, the timestamp channel. The transmission begins with a LO bit (far left), then the sixteen sample bits, most significant first and least significant last. The rightmost, least significant, bits appear to have two values at once because they are changing state even as we take the photograph. The dots in the transitions are the steps in the rising edge caused by reflections.

The X2 output has a rest state of 3.3 V, or logic HI. To initiate serial transmission, it asserts a 0.0 V, or logic LO, for one 4-μs bit period. It proceeds from there to transmit the sample bits one at at time, from the most significant to the least significant.

Figure: Transmission Scatter Seen on X2 from a 512 SPS Transmitter.

If we expand the oscilloscope view, we start to see subsequent samples. The photograph above shows the subsequent sample transmissions when we select a 512 SPS transmitter. Transmitters have sample scatter, as we describe elsewhere. Thus the samples do not arrive at a uniform rate, but rather at an average rate of 512 SPS.

Firmware V6: We configure X1 and X2 to be digital outputs set by LWDAQ Commands. The Immediate Sample Transmission of V5 now goes to Y2 and the Antenna One receiving signal goes to Y1. To set X1 to 1, or 3.3 V output, we transmit command 0x0104 to the A3027C (the 0x is for hexadecimal notation). To clear X1 to 0, or 0.0 V, we transmit 0x0004. To set and clear X2 we transmit 0x0108 and 0x0008 respectively. We can transmit these commands with the Diagnostic Instrument, which we set up like this. We set the transmit command in hexadecimal notation and press Transmit to send the command to the Diagnostic Instrument's target device.

The following oscilloscope traces show X1 and X2 being switched by the Diagnostic Instrument. We enter two commands and the Diagnostic Instrument will transmit both of them sequentially.

Figure: Switching X1 and X2 with Firmware V6. Top trace is X1, bottom trace X2. We have transmit commands "0104 0108 000C" being sent repeatedly. The result is that X1 goes HI (3.3 V), then X2 goes HI, then both go LO.

Because the immediate sample transmission is now a low-voltage differential signaling (LVDS) output, it's transitions are a thousand times faster than when they emerged on X2.

Figure: Immediate Sample Transmission on Y2 in Firmware V6. The logic transitions now take nanoseconds rather than microseconds.

In future versions of the firmware, it will be possible to reduce the clock speed of the sample transmission, from the existing 4 μs to 50 ns.

Firmware V7: We configure X1 to produce 1-ms, 3.3-V pulses at 24.6 Hz when we write 0x0104 to the A3027, and a continuous 0 V when we write 0x0004. Thus we replace the HI of Firmware V6 with a sequence of pulses. We intend for these pulses to be used to trigger image capture by closed circuit television recorders. The Y2 output is Immediate Sample Transmission, controlled as in Firmware V6.

Firmware V8: A prototype of Firmware V9 in which the message notification worked poorly. Exists only in receiver P0245. We restore immediate sample transmission to X2.

Firmware V9: The differential outputs, Y1 and Y2, transmit message notifications. These are 36-bit serial words transmitted at 20 MBPS (50 ns per bit). There are three types of notification. The first is message incoming, which the A3027 transmits when one of its message decoders has received eight complete and correct bits of a twenty-four bit message. The second is clock message, which carries the value of the A3027's clock. The third is data message, which carries the channel number, contents and timestamp of a data message.

Figure: Message Notification on Y1/Y2. The bottom trace is the transmit bit output from an A3028A dual-channel transmitter. The top trace is the message notification signal sent out of Y1 and Y2.

In the figure above, we see the Y1/Y2 signal is by default HI (1). The message incoming notification takes place roughly half-way through the transmitter radio-frequency burst, following eleven start synch bits, a start bit, and eight data bits received. The notification is a serial transmission of the value 0xA, followed by all ones. When the message has been decoded, we have a message data notification, which begins with the value 0xC, followed by the eight-bit channel number, sixteen bits of data, and an eight-bit timestamp. Clock messages are transmitted in a similar way, starting with value 0xB, eight zeros for the clock channel number, the top sixteen bits of the timestamp, and then the A3027 firmware version number.

In order to guarantee that all clock messages stored by the A3027 are transmitted in the notification data stream, all message notifications and incoming notifications are suppressed for 30 μs before each clock message. The clock messages are saved every 7.8 ms, so we miss 0.3% of data messages in this way.

The Message Notifications are designed for use with the Animal Location Tracker (A3032A). The X1 output is set by a LWDAQ command. To set X1 to HI, or 3.3 V, transmit 0x0104. To clear X1 to LO, or 0.0 V, transmit 0x0004. The X2 output is Immediate Sample Transmission, as in Firmware V5.

Firmware V10: Adds support for set numbers. All SCTs belong to a transmitter set between 0 and 13. By default, Firmware V10 responds only to channels 1-14. It is possible to write to a four-bit register on the A3027 to change the set number it records from, although access to this register is not provided by the latest Receiver Instrument or Neurorecorder Tools. Firmware V10 provides a four-bit register space sixteen registers long. The first register, address zero, controls X1. To set or clear X1 we transmit LWDAQ device command 0x0104 and 0x0004 to the A3027 device. To assign the value S to the Set Select Register, we write to the second register, address one, with 0x1s04, s is the hexadecimal representation of S. The remaining fourteen registers are available for future use. If we write value 0xF (decimal 15) to the Set Select Register, the A3027 will accept messages from all sets. If two transmitters have the same channel number, but different set numbers, their signals will be combined into the same channel. For example, channel 17 and channel 1 will be combined into channel 1. The X2 output is Immediate Sample Transmission, as in Firmware V5.

Firmware V11: Supports channel numbers 1-254 as described here. By default, however, FV11 responds only to channels 1-14. Identical to firmware V10 except for two changes. The set number is always stored in the top four bits of the channel number. When all sets are being recorded, duplicate messages are not elimiated. If eight antennas receive the same message, eight copies will be stored. The Receiver Instrument ipurges duplicates as soon as it receives them, but they must still be downloaded. Immediate sample transmission as for FV = 5.

Firmware V12: Supports channel numbers 1-254 as described here. By default, however, FV12 responds only to channels 1-14. Duplicate reduction replaces duplicate elimination. We remove >99% of duplicates. The remaining duplicates are eliminated by the Receiver Instrument. The X2 output is Immediate Sample Transmission, as in Firmware V5.

Video: How to Set and Clear Logic Output X1 on an A3027. In this 150-s video, we demonstrate how we can set and clear the 3.3-V logic output X1 using the LWDAQ Diagnostic Instrument. This procedure works with Firmware V8+.

If your Octal Data Receiver (A3027) is equipped with Firmware V12, you will be able to record from all channel numbers 1-254, but only after the Receiver Instrument or Neurorecorder Tool has configured the A3027 to accept all channel numbers. Modern Receiver Instrument and Neurorecorder Tools automatically configure your A3027 to record from all channel numbers 1-254. But if you press the reset button on the front of an A3027 with firmware V12, the firmare will go back to detecting only channel numbers 1-14. This behavior leads to confusion in several situations. If you connect power to your A3027 with FV12, connect an antenna and turn on a transmitter with channel number 1-14, an activity light will illuminate on the front panel. But if you turn on a transmitter with channel number 17-254, no light will turn on, even if the second transmitter is running. Now you use the Receiver Instrument to download data from the first transmitter, and suddenly you see two lights. The A3027 is receiving from both transmitters. Later, you stop downloading. You come back the next day. You turn on both transmitters and both activity lights illuminate. You press the reset button on the A3027, or you unplug and plug in power, and one of the two lights goes off. Or you can imagine having ten transmitters all with channel numbers greater than 14, and you sometimes see activity, sometimes you do not, depending upon whether the A3027 has been reset by the Receiver Instrument or Neurorecorder Tool.

Firmware V13: As V12, but default configuration is to detect all channel numbers, rather than only 1-14. We also correct an error in implementation of antenna activity lights. The X1 output is user logic output as in FV6. The X2 output is Immediate Sample Transmission, as in FV5. The Y1 and Y2 outputs are both dedicated to message notification for location trackers.

Firmware Reprogramming

[28-FEB-17] There are three programmable logic chips in the A3027 enclosure. The Message Router chip controls how transmitter messages are stored in memory and uploaded to the LWDAQ Driver. In firmware version xx, the Message Router logic is defined in source file P302701Axx.abl. We program the chip itself with compiled file P302701Axx.jed. The second logic chip is the Message Decoder, which controls how incoming bit sequences are received. The Message Decoder is defined by P302702Axx.abl and programmed by P302702Axx.jed. The third logic chip is the Display Controller, which we define with P302703Axx.abl and program with P302703Axx.jed. The Message Router and Message Decoder are both on the main circuit board inside the A3027 enclosure, and we program them with one operation. The Display Controller chip is on the circuit board behind the display lights, and we program it with its own operation. Most likely, you will not have to upgrade your display board firmware, so the only operation you need to perform to update your A3027 firmware is to re-program the Message Router and Message Decoder on the main circuit board.

The A3027 logic chips are manufactured by Lattice Semiconductor. To re-program them, you need the programming cable and software. The cable is described on-line here. The programming cable is available from DigiKey and RadioSpares. The Windows version of the programming software you can download here. There is a Linux version also, but we do not maintain a copy of the Linux version ourselves. There is no MacOS version. The programming cable comes with many wires and a single-row eight-way socket adaptor that you use to connect the wires called VCC, TDO, TDI, TMS, GND, and TCK to the circuit you want to re-program. The following movie shows you how to attach the wires to the adaptor.

Video: How to Assemble the Terminating Connector of the Lattice Semiconductor Programming Cable.

In the programming software, select Help and search for "USB Driver". Follow instructions to install USB port drivers. If the program tells you the drivers are already installed, re-install them. Plug the programming cable into your computer when the installer asks you to do so. Install all versions of the USB driver. Restart the programming software. You are now ready to reprogram the logic chips. In the following movie, we reprogram the two logic chips on the main circuit board.

Video: Overview of Firmware Reprogramming. Here we are using the older, ispVM version of the programming software.

The software procedure is slightly different for the newer version of the programming software. We demonstrate the newer procedure in the video below.

Video: Using the Diamond Stand-Alone Programming Software.

If the software scans the A3027 firmware correctly, but fails to program the firmware afterwards, go into the programmer software settings and adjust the programmer configuration by clicking "continue download on error". We have had to make this adjustment on some virtual Windows machines. The programming will now proceed, but you will get a warning at the end. In our experience, the firmware will be loaded correctly into the A3027 despite the warnings.

The programming software takes JEDEC files as input. The following table provides links to the JEDEC files you need for various firmware versions. In order to show when you have to reprogram the Display Controller, we provide the earliest version of Display Controller firmware that is compatible with each overall firmware version number. Firmware versions 4-12, for example, all use the Display Controller firmware of Firmware Version 4. So if your existing firmeware version is 4 and you are upgrading to 12, you don't need to re-program the Display Controller on the display board.

Determine the firmware version of your A3027 by looking at the Receiver Instrument panel, where there is a firmware version display box. The firmware version will be displayed with 30 added to it, so 42 is firmware version 12.

Once you have downloaded the JEDEC files you need, scan the programming connector on the A3027 with the programming cable using the Scan button in the programming software. A new window will open and you will see two logic chips listed in the programming cable window. By clicking on the file entry box next to each logic chip, you can associate each chip with a JEDEC file. The first chip listed is the Message Router, which takes the 01Axx.jed files and the second is the Message Decoder, which takes the 02Axx.jed files. Press Go and the programming begins. When it is done, unplug the cable and test the A3027. You can reprogram the firmware as often as you like.

Indicator Lamps

[28-JUN-25] There are a total of thirty indicator lamps on the front panel of the Octal Data Receiver (A3027). Fifteen of them along the top are Channel Activity lamps. These are numberd 1-15. Those numbered 1-14 are white. The 15th is blue. These lamps turn on when samples are received on certain telemetry channels. Any of the channel numbers 1-254 can be used for telemetry, excepting those channel numbers that are exactly divisible by 16. If we turn on a transmitter, one of the activity lights will turn on. Given a transmit channel number, we determine which activity light will turn on by dividing the channel number by sixteen and taking the remainder. The remainder gives us the activity lamp number that will illuminate. So channels 1, 17, 33, and 49 all cause activity lamp number one to turn on. Channels 14 and 94 both cause lamp number fourteen to turn on. Lamp number 15 is for channel numbers with remainder 15. This lamp is blue, because all these channel numbers are reserved for metadata transmission. Metadate transmission are used by Implantable Stimulator-Transponders (ISTs) for acknowledgements and reporting.

If you find that your channel and antenna activity lamps are behaving erratically, check the firmware version of your A3027. For example, if the activity lamps for some of your transmitters turn on, and then after you press the reset button on the A3027, they turn off, or they turn off after you unplug and plug in the network cable at the back of the A3027. Or perhaps you notice that, as soon as you contact the A3027 with the Receiver Instrument or Neurorecorder Tool, some of the activity lights turn on. You will see the firmware version reported in both the Receiver Instrument and the Neuroplayer Tool. If your A3027 has Firmware V12, lamps will illuminate for channels greater than fifteen only after you configure the A3027 using the Receiver Instrument or Neurorecorder Tool. After you press the A3027's reset button, Firmare V12 will stop recording channel numbers greater than fifteen, so lamps corresponding to these channels will extinguish.

The A3027 channel activity lamps shine with a brightness proportional to the number of samples being received on corresponding channels per second. The brightest they will get is when we are receiving roughlky 2048 SPS. If two transmitters with 512 SPS are sharing the same channel activity lamp, we will be able to tell when we turn one of them on and off because the lamp will get brighter and dimmer.

There are eight Antenna Activity lamps, one for each of the eight antenna inputs on the A3027. These shine in proportion to the number of samples being received by each of the eight inputs. They show us which antennas are receiving telemetry signals.

The remaining indicator light are for power, reset, activity, and empty data buffer. Press the HIDE button and all lamps except HIDE and the power lamps will turn off. Turning off the lamps reduces disturbance to the animals at night.

Design and Development

[27-JUN-25] For design files and development logbook, see the A3027 design and development page at D3027.