This is a small CAN based Time-of-Flight (TOF) sensor. It determines the distance to an object and sends the resulting message on the CAN bus.
The block diagram is shown below. The design consists of an input buck regulator. The regulator should be good up to 24V, but was designed to work at 12V. There is reverse battery protection, so it should handle accidentially connecting the battery up in reverse.
The buck generates 5V which is used for the CAN transceiver. The 5V is fed to two LDO's to generate 3.3V for the processor and 2.8V for the TOF sensor.
There are two status LEDs on the board. An STM32G431 processor powers everything.
There are three user accessible connectors: Main J3:
| Pin | Use |
|---|---|
| 1 | Power |
| 2 | Ground |
| 3 | CAN High |
| 4 | CAN Low |
The mate is a JST PHR-4
There is a standard USB Micro B connector that connects to a PC. It enumerates as a serial port.
The software uses the STM32CubeIDE to build the code. I really wanted to use CMake with the CubeMX tool, but I was having trouble getting the code to work correctly. So CudeIDE for the win.
The code is SUPER simple. It just reads the TOF sensor once every 100 ms and sends out a CAN message.
The CAN message is defined as:
| Byte | Definition |
|---|---|
| 1 | API Status |
| 2-3 | distance in mm |
| 4-5 | ambient Mcps |
| 6-7 | signal Mcps |
The API Status is the not well defined. If the value is zero, the distance is valid. The distance is in millimeters. The Ambient and Signal values are in Millions of Chips Per Second.
The CAN ID is based on the WPILib CAN interface:
Device Type is Misc (10) Manufacturer is 20 API Class is Status (5) API Index is 0 Device Number is currently 0 (need to figure out how to have several of these on the bus)
It is assumed you are using a JLink and it is installed in /opt/SEGGER/JLink In the scripts directory:
- Run gdbstart.sh in one terminal
- Run debug.sh in other terminal. You now have the full power of GDB at your literial finger tips
There is no ability to upgrade the firmware right now. It will be fixed in future PCB rev. Currently you have to JTAG/SWD the firmware.