I am testing a custom board prototype and having trouble getting I2C to work.
During testing, I was able to observe activity on the SDA line, although it consisted of only a single-bit pulse with no address. I also observed a clock signal on SCL when I added an additional pull-down resistor to the SDA line (I discovered this while checking for shorts), which was quite confusing. However, I now suspect that this was simply undefined hardware behavior resulting from an invalid pin configuration.
Initially, I was using P2.03 as SCL and P2.04 as SDA, but then I noticed that TWIM has a clock pin requirement. I made a hardware workaround to move SCL to P2.01, but the behavior remained the same.
I then noticed another requirement in the datasheet stating that a peripheral can only use GPIOs from the same power domain. According to the block diagram, GPIO port P2 belongs to the MCU power domain, and I do not see any TWIM peripheral in that domain. TWIM peripherals appear to be available only in the PERI PD (GPIO ports P1 and P3) and the LP PD (GPIO port P0).
Could you please confirm whether my understanding is correct? Are there any other restrictions that I should be aware of?
Also, could I use something like CONFIG_I2C_BITBANG to work around this issue on the current board so that I can test the rest of the hardware before ordering a revised board with the correct design?