Telemetry Control Box (TCB)

© 2022, Kevan Hashemi, Open Source Instruments Inc. © 2022, Nathan Sayer, Open Source Instruments Inc.

Contents

Description
Versions
Design
Set-Up
Operation
Power Consumption
Modifications
Development

Description

[07-SEP-22] The Telemetry Control Box (TCB-A) is a telemetry receiver and motion sensor for our Subcutaneous Transmitters (SCTs). The TCB-A16 comes with sixteen Loop Antennas (A3015C) and coaxial cables that we connect to the TCP-A16's sixteen independent antenna inputs. Each input decodes telemetry messages and measures their power at the antenna. The power measurements allow us to estimate the location of all transmitters in the telemetry system. The antenna that receives the most power from a transmitter is most likely going to be the antenna to which the transmitter is closest. These same power measurements allow us to measure the activity of animals, just as we do with our Animal Location Tracker (A3038). All versions of the TCB connect directly to Power over Ethernet (PoE), from which it obtains power and through which it performs all communication.


Figure: Sixteen-Way Passive Feedthrough. This assembly is part of the TCB-A16.

The TCB-A16 replaces the Octal Data Receiver (A3027E, ODR). The TCB-A16 provides sixteen antenna inputs, the ODR provided eight. The TCB-A16 provides antenna power measurements, the ODR did not. Unlike the ODR, the TCB-A16 does not require a LWDAQ Driver (A2071E). If we combine the TCB-A16 with the synchronous video provided by our Animal Cage Cameras (AACs), the TCB-A16's location tracking allows us to determine which animal is which in the video.

The Telemetry Control Box Version B (TCB-B) adds a command transmitter for every antenna connection, so that we can use any of its antennas to transmit commands devices capable of receiving commands, such as our Implantable Stimulator-Transponders (ISTs). For reliable reception by an IST, we need to choose the antenna from which the IST will receive the strongest signal. The TCB-B16 provides sixteen antenna inpugs. We select the best antenna in the following way: we transmit an XON command through all sixteen antennas consecutively so as to make sure our target IST is transmitting its synchronizing signal. The synchronizing signal is just like an SCT signal, so the TCB-B16 will tell us which antenna is receiving the signal with the greatest power, and we choose this antenna to transmit a subsequent stimulus command. The TCB-B16 replaces the Command Transmitter (A3029) and LWDAQ Driver (A2071E), combining command transmission and telemetry reception into one instrument with one PoE connection, greatly simplifying our data acquisition and control system.

Versions

The following versions of the Telemetry Control Box (A3042, TCB) exist.

Version Dimensions Comment
TCB-A16 55 cm × 35 cm × 12 cm Sixteen-way receiver and activity monitor.
TCB-B16 55 cm × 35 cm × 12 cm Sixteen-way receiver, activity monitor, and command transmitter.
Table: Versions of the Telemetry Control Box (A3042, TCB).

The following sub-assembly versions exist.

Version Comments
A3038BB-D2 ALT Base Board, no detector coils, re-programmed with P3042BB.
A3038DM-C2 ALT Detector Module, unshielded, firmware P3038DM.
A3038DM-D3 ALT Detector Module, shielded, firmware P3038DM.
A3042DP-A Display panel with lights and switches, firmware P3042DP.
A3042PF-A16 Sixteen-Way Passive Feedthrough.
A3042TF-A16 Sixteen-Way Transmitting Feedthrough.
Table: Sub-Assemblies of the Telemetry Control Box (A3042, TCB).

Design

[15-SEP-22] We make the TCB-A16 by taking an Animal Location Tracker (A3038A), putting it in a box, connecting the detector modules to BNC sockets a Sixteen-Way Passive Feedthrough (A3042PF-A16) on the back wall of the box, connecting a Display Panel (A3042DP-A) to the base board, and fastening the display panel to the front of the box. We connect the ALT's RJ-45 socket to an RJ-45 feedthrough on the back wall of the box. The TCB comes with sixteen A3015C antennas and an Ethernet jumper cable so we can connect it to a PoE switch.

We make the TCB-B16 in the same way, but we use an Animal Location Tracker (A3038C), which provides sixteen detector modules, thus allowing the TCB-B16 to provide sixteen antenna connectiobns. The TCB-B16 is identical to the TCB-A16 except its antenna connections pass through a Sixteen-Way Transmitting Feedthrough (A3042TF-A16) on the back wall, which we wire to the base board so as to control the feedthrough's sixteen independent command transmitters, which we connect to the antennas with radio-frequency switches when we want to use an antenna for command transmission.

The P3042BB firmware is for the logic chip on the base board. This firmware is similar to the ALT Base Board firmware except for the addition of communication with the display board and transmitting feedthrough. We use C3038BB for the RCM6700 module, same code as for the ALT LWDAQ Relay. We use P3038DM on the detector modules, same code as for the ALT Detector Modules. We use P3042DP on the display panel and P3042TF on the transmitting feedthrough.

S3042DP_1.gif: Schematic of A3042DP-A Display Panel.
A304201A.zip: Geber files for A3042DP-A PCB.
A304202A.zip: Geber files for A3042PF-A16 PCB.
Code: Compiled firmware, test scripts.
P3042BB: Base board firmware and software repository.
P3042DP: Display panel firmware repository.
P3038DM: Detector module firmware repository.

Set-Up

[27-JUL-22] Connect the TCB to a PoE switch that can supply at least 10 W of power to the device. Connect your data acquisition computer to the same switch. Connect coaxial antennas to the TCB's antenna inputs by passing cables through the walls of your Faraday enclosure using feedthrough connectors on the back wall or feedthrough assemblies on the floor. Set up the TCPIP connection between your computer and the TCB using our SCT setup instructions.

Operation

[27-JUL-22] See SCT Setup Instructions.

Power Consumption

[27-JUL-22] The TCB-A16 and TCB-B16 consume a maximum of 8 W quiescent current. The TCB-B16 peak power consumption during command transmission is 10 W.

Modifications

[27-JUL-22] None yet.

Development

[07-MAR-22] Nathan reports as follows. "The system is a simple setup of two plastic cages taped together with an antenna on opposite sides. The antennas are spaced 70cm apart. I turn off all the detector modules except for the two that are taped to the sides of the cages. I turn on a transmitter inside the faraday canopy and move the transmitter around the center of each cage, changing position and orientation. I notice that when the transmitter is moving in the center of the cage (about 3 times closer to one antenna than the other) the tracker in the Neuroplayer displays the transmitter being on the correct antenna approximately 95% of the time. That is to say that in this two-antenna system, if an animal was moving in the center of a cage there is a 95% chance that our system would detect that mouse being in the correct cage."


Figure: Animal Location Tracking with Loop Antennas. We have two A3015C antennas on either side of two animal cages. Antennas are connect to detector modules on an A3038C ALT.

[21-MAR-22] We are comparing the Telemetry Control Box to the Octal Data Receiver. Nathan writes, "I'm still working on what went wrong with the coaxial combiner, but I was able to get some reception readings that are consistent with past ones so I went ahead and compared the two receptions. I began by only connecting one antenna and comparing reception on different types of transmitters. My results are as follows: For the Faraday canopy test transmitter that is taped onto the end of a stick, I got 75% reception using the ODR as well as the TCB while moving the transmitter to various places in the canopy. Using the rat transmitter, I got 85% reception on both receivers. Similarly, I got 85% reception on both receivers using the pup transmitter with a worse antenna and 90% reception on both receivers using the pup transmitter with the better antenna. None of the transmitters gave different amounts of reception on one receiver than the other. To confirm this, I did another experiment where I moved around each of the transmitters individually while the coaxial combiner output was sent to a T-junction that split to both receivers. This way I could see how much reception I am getting from both receivers at the same time. I never encountered a situation in which I was getting reception on one receiver and not on the other."

Here we see that, by splitting the antenna signal and sharing between the two receivers, we can watch the reception lights provided by both receivers to see if they are synchronous. We find they are: reception by the ODR implies and is implied by reception by the TCB, even though the ODR and TCB do not use the same detection method. The ODR uses a hetrodyning receiver with active demodulator. The TCB uses a direct, narrow-band amplifier with split-capacitor tuner and crystal diode demodulator.

[27-JUL-22] The Display Panel (A3042DB-A) printed circuit board A304201A is almost ready for fabrication. We begin work on the Passive Feedthrough (A3042PF-A16) printed circuit board A304202A. We will be using an ALT Base Board (A3038BB-D), but we will remove its antennas and we will program the board with firmware P3042BB that re-assigns detector control bus lines DC5 and DC6 for use by the display panel through the flex connector at the end of the detector module daisy chain. We will likewise re-program the A3038DM-C detector modules with firmware A3042DM so that they turn on their lights with DMRST and have no HIDE function, which we don't need inside the TCB box.

The base board will use DC5 to transmit to the display board. The display board will use DC6 to transmit to the base board. We still have TP1, TP2, TP3, and TP4 free on the base board to use for communication with the trasmitting feedthrough. The base board logic will use DC5 to transmit eight-bit serial messages. The first four bits will be an operation code 0-15. The next four bits will be an operand 0-15. Here are the messages the base board will be able to send to the display board.

Opcode Operand Function
1 n Message received from SCT channel with lower nibble n
2 b ACTIVE = b
3 b DMERR = b
4 b UPLOAD = b.
5 b EMPTY = b.
Table: Base Board to Display Panel Messages. Operand is n for 0-15 or b for 0 (false) or 1 (true).

Here are the messages the display board will be able to send to the base board.

Opcode Operand Function
6 b CONFIG = b
8 b RESET = b
Table: Display Panel to Base Board Messages.

The transmitting feedthrough will need to receiver serial messages also, so as to select one of sixteen antennas and prepare them for power transmission. The switching of the power itself for command transmission to crystal radios we wil perform with a dedicated logic line that enables the chosen RF oscillator when it is asserted. We expect to use TP3 for serial selection of antenna and TP4 to turn on RF power. The transmitting feedthrough's logic will disable command transmission automatically after a short silence, perhaps as short as 10 ms.

[22-AUG-22] We have the first A3042PF-A16 assembled and tested. We have the A304201A and are starting assembly. We note inconsistent masking of vias.


Figure: Inconsistent Via Masking on A304201A.

[07-SEP-22] The detector control bus on the base board consists of eight single-ended logic lines. Their functions in the A3042BB will be as follows.

Schematic
Name
Firmware
Name
Direction Function
DC0 DMRST Bidirectional Detector Module Reset. Reset display panel, base board, and feedthrough.
DC1 DRC Output Detector Readout Complete. Tells detector modules to release data bus.
DC2 DMERR Input Detector Module Error. A detector module is malfunctioning.
DC3 INCOMING Bidirectional Message Incoming. All detector modules must measure signal power.
DC4 RECEIVED Bidirectional Message Received. All detector modules must record message.
DC5 SDI Input Serial Data In. Receive serial messages from display panel.
DC6 SDO Output Serial Data Out. Transmit serial messages to display panel.
DC7 DMCK Output Detector Module Clock. The single 8-MHz clock used by the detector modules.
Table: Detector Control Bus Signals in the A3042BB. We gif "direction" with respect to the base board.

The display panel will receive serial messages on DC6 (SDO) and transmit serial messages on DC5 (SDI). The protocol assumes that both the base board, detector modules, and display panel have pull-down resistors on SDO and SDI respectively. Timing of the protocol as shown below. The DC6 signal doubles as SHOW for the detector modules. When we press the SHOW button on the base board, SDO will be asserted at all times except during serial communication, when we will see two LO setup bits, a HI start bit, eight data bits, and then HI in response to SHOW after that. Without SHOW, SDO will go LO after transmission.


Figure: Serial Protocol for Communication Between Base Board and Display Panel.

When the Display Panel sees DC0 (DMRST) go HI, it will illuminate its RESET lamp and reset its state machines. When the Display Panel sees its RESET button pressed, it will assert DMRST. This will, of course, reset its own state machines. The Base Board will detect the HI on DMRST and assert a global hardware RESET. When the Display panel sees its CONFIG button pressed, it will send a CONFIG message to the Base board. When the Display Panel sees DC2 (DMERR) HI, it will illuminate its DMERR lamp.

[15-SEP-22] Create P3042BB repository for base board firmware and software. We start with version 1.0 based upon P3038BB v8.3. We change firmware version to 1, change receiver type to 120 so the Neurorecorder can identify the TCB. Now have v1.1. Begin adding code for communication with display panel. Plan is to leave the detector modules as they are, and use SHOW and HIDE lines for communication.

[16-SEP-22] We have P3042BB v1.2 transmitting display messages on SDO = DC6. When the base board's SHOW button is not depressed, serial communication is as shown below, with LO before and after.


Figure: SDO with SHOW Button Not Pressed. The SCT is channel No228, which has remainder 4 when divided by sixteen.

When SHOW is depressed, we have HI before and after transmission, but we have 2 μs of LO before the start bit.


Figure: SDO with SHOW Button Pressed. The SCT is channel No228, which has remainder 4 when divided by sixteen.