Firmware for Hardware Validation
Writing firmware may be hard, but building hardware to run that firmware is often harder. A common problem is being unsure if an external IC is connected properly, since functionality is hard to test with just electrical bench tools. This can be helped from the firmware side with ‘smoke tests’: projects that engage an IC with as little user input as possible. These would differ from the actual board firmware project in that they
Some examples of what a smoke test might do are as follows:
For most ICs, periodically read a manufacturer-set status register and compare the read value to the expected value, logging the results
For an ADC (e.g. ADS1015), periodically take readings and log output
For a serial to CAN converter (e.g. MCP2515), periodically send CAN messages and log whatever is received
For a multiplexer (e.g. ADG731), periodically cycle through all possible outputs, flipping pins
For a demultiplexer (e.g. ADG731), periodically cycle through all possible inputs, perhaps taking readings with the STM’s onboard ADC
For a switch (e.g. BTS7040), periodically toggle on and off
Combining these, it would also be useful to have a smoke test for an entire board. For example, a smoke test for the pedal board might periodically read from each ADC channel. A smoke test for the center console might log all GPIO button presses to ensure all of them are wired correctly.
IC list to write smoke tests for
BMS AFEs
LTC6811 via SPI
ADG731 via LTC6811 via SPI
BMS Current sense
ADS1259 via SPI
MCI
MCP2515 via SPI
Solar Sense
SPV1020 via SPI and MC74LVX138 demuxer
MCP3427 via I2C
Pedal Board
ADS1015 via I2C
Power Distribution
PCA9539r via I2C
MCP23008 via I2C
BTS7200
BTS7040 / BTS7080