We are working with the nRF52840 and an ADC chip that is capable of I2C communication faster than 400 KHz, allowing lower latency. I know that the nRF52840 does not officially support TWI Clock rate faster than 400 KHz, but I have read some forums about people that managed to do this on an nRF52832 at 800 KHz. We tried the same approach with our nRF52840, but weren’t successful. Is there any way to do this with our chip?
I'm sorry, but we do not recommend nor support using the TWI at a faster rate than 400kHz. The chip has not been tested for the usage of higher frequencies than this, so there's no telling what will happen if you choose to do so.
Would you be able to lead us in any direction to try increasing the TWI rate even though it may not work?
You can try setting the frequency register to a higher value than it is. Please see the TWI_FREQUENCY_FREQUENCY defines in the nrf52840_bitfields.h header in the SDK (lines 13966-13971). Please note that I haven't tested this, so I don't know the outcome. Please see this thread for more info on the baud rate generator. All peripherals use the same one, so don't mind it saying UART.