Luca's Notes

Logging and Telemetry Board

3 min read

This is a new board on FS-4. It’s purpose is to read from the CAN bus and record that data, as well as transmit it over a wireless connection to a base station, which can then relay it to a database hosted on the internet for live viewing by the whole team.

Unlike previous years, the logging telemetry board will not have a microcontroller and will instead be a “hat” which sits upon any SBC with the standard 40 pin header, which must have I2S, I2C, UART0, and SPI0,1 matching the raspberry pi spec. This decision was made because:

  • It is difficult to write lots of data to an SD card from a MCU The software needed for TCP/IP communication and to interface with either the Teledatics or Heltec (or seeed) module only really exists as a linux module…
  • Writing such a big driver is a lot of work
  • Logging using the linux can-utils package has already been tested at norcal, and works well

The board will have the following features:

  • 3 can peripherals capable of up to 12 Mbps
  • Audio codec to run driver audio comms
  • Robust automotive 12v power input
  • Alternate M.2-E and PCIe 802.11ah HaLow card support
  • RTC

Current work

See this subfolder, and it’s readme, and it’s schematic pdf When PCB’s are ordered, a static version of relevant documents will be placed here.

A working prototype

A “vibes” first try schematic

Issues:

  1. I made this schematic in kicad nightly, so it needed to be redone
  2. It cannot be collaborated on well, because it does not take advantage of hierarchical sheets
  3. There’s no architectural support for an alternative module

V1 (Fabbed) board

PDF Schematic

  • Only one CAN channel populated (of 3)
  • Wrong size pin headers.. needed to be soldered partially inserted

Software Bringup

FTDI chip was out of stock, so configured USB-OTG Serial…

  1. dtoverlay=dwc2 → /boot/config.txt
  2. modules-load=dwc2,g_serial after rootwait in /boot/cmdline.txt
  3. ln -s root/lib/systemd/system/getty@.service root/etc/systemd/system/getty.target.wants/getty@ttyGS0.service
  4. echo pi:$(echo 'mysecretpassword' | openssl passwd -6 -stdin) > boot/userconf

Wireless to eduroam using nmtui

  1. Set device up using sudo ip link set wlan0 up
  2. Set device up in nmtui->radio
  3. Configure network using “add connection”

Setup the RTC

  1. dtoverlay=i2c-rtc,pcf8523 → /boot/config.txt
  2. timedatectl status to confirm functionality

CAN

  1. sudo apt-get install can-utils
  2. Into boot/config.txt:
dtparam=spi=on
dtoverlay=spi1-1cs
dtoverlay=spi1-1csdtoverlay=mcp251xfd,spi1-0,interrupt=26,oscillator=20000000
  1. sudo ip link set can0 type can bitrate 500000

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