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

[10-AUG-22] The Telemetry Control Box (TCB-A) is a telemetry receiver and motion sensor for our Subcutaneous Transmitters (SCTs). The TCB-A15 comes with fifteen Loop Antennas (A3015C) and coaxial cables that we connect to the TCP-A15's fifteen 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.

The TCB-A15 replaces the Octal Data Receiver (A3027E, ODR). The TCB-A15 provides fifteen antenna inputs, the ODR provided eight. The TCB-A15 provides antenna power measurements, the ODR did not. Unlike the ODR, the TCB-A15 does not require a LWDAQ Driver (A2071E). If we combine the TCB-A15 with synchronous video, such as recorded by our animal cage cameras (AACs), the TCB-A15 allows us to identify animals seen in the video by correlating their movements with the movements of their implanted transmitters as deduced from the antenna power measurements.

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
TCP-A15 55 cm × 35 cm × 12 cm Fifteen-way receiver and activity monitor.
TCP-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-D ALT Base Board, antennas removed, re-programmed with P3042BB.
A3038DM-C ALT Detector Module, unshielded, re-programmed with P3042DM.
A3042DP-A Display panel with diagnostic lights and switches.
A3042PF-A15 Fifteen-Way Passive Feedthrough.
A3042TF-A16 Sixteen-Way Transmitting Feedthrough.
Table: Sub-Assemblies of the Telemetry Control Box (A3042, TCB).

Design

[26-JUL-22] We make the TCB-A15 by taking an Animal Location Tracker (A3038A), putting it in a box, connecting the detector modules to BNC sockets a Fifteen-Way Passive Feedthrough (A3042PF-A15) 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-A15 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. We use C3038BB for the RCM6700 module, same code as for the ALT. We use P3042DM on the detector modules, P3042DP on the display panel and P3042TF on the transmitting feedthrough. We plan to put all these projects on GitHub.

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-A15 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 crystal radio.

[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 as a serial logic line. This leaves DC6 free for later use on the display panel. We still have TP1, TP2, TP3, and TP4 free for use with the trasmitting feedthrough. The base board logic will use DC5 to transmit eight-bit serial instructions. The first four bits will be an operation code 0-15. The next four bits will be an operand 0-15.

Opcode Operand Function
0 1 Force all signal lights to turn on (pressing SHOW).
0 0 Stop forcing signal lights to turn on (release SHOW).
1 1 Disable all signal lights (toggled by pressing HIDE).
1 0 Enable all signal lights (toggled by pressing HIDE).
3 n Flash white reception light n for 1 ms.
4 0 Turn off ethernet yellow light.
4 1 Turn on ethernet yellow light.
5 0 Turn off UPLOAD and EMPTY light.
5 1 Turn on UPLOAD, turn off EMPTY light.
5 2 Turn off UPLOAD, turn on EMPTY light.
5 3 Turn on UPLOAD and EMPTY light.
Table: Display Panel Instructions.

If we feel it helpful, we will allow DC6 to be used by the display panel to send information back to the base board logic. The transmitting feedthrough will need to receiver serial commands 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.