I2C frequencies below 100kbps

[nategreco]

Due to board design flaws that led to insufficient rise time for 100kbps communication, I would like to configure my i2c node in the device tree with a baud rate of 10 kbps.  At build time I get the following build failure:

C:\ncs\v2.1.0\zephyr\include\zephyr\toolchain\gcc.h:77:36: error: static assertion failed: "Wrong I2C 1 frequency setting in dts"
   77 | #define BUILD_ASSERT(EXPR, MSG...) _Static_assert(EXPR, "" MSG)
      |                                    ^~~~~~~~~~~~~~

This is checked in `i2c_nrfx_twim.c`:

#define I2C_NRFX_TWIM_FREQUENCY(bitrate)				       \
	(bitrate == I2C_BITRATE_STANDARD  ? NRF_TWIM_FREQ_100K :	       \
	 bitrate == 250000                ? NRF_TWIM_FREQ_250K :	       \
	 bitrate == I2C_BITRATE_FAST      ? NRF_TWIM_FREQ_400K :	       \
	IF_ENABLED(NRF_TWIM_HAS_1000_KHZ_FREQ,				       \
	(bitrate == I2C_BITRATE_FAST_PLUS ? NRF_TWIM_FREQ_1000K :))	       \
					    I2C_NRFX_TWIM_INVALID_FREQUENCY)

I suspect the answer is no but just want to double check before I wait on building another board - Could the driver support a lower baud rate if I modified this section of code?

Details:
nRF Connect SDK - v2.1.0

nRF52840

[Turbo J]

Nope - if your read the PS, those constants are the only values that the hardware supports. The 100kBps is the minimum.

However,  the hardware supports clock stretching. That could help you in some cases depending how much control you have over the slave.