Can't write more than 16 bytes using i2c_transfer() on nRF5340 DK

RE: Can't write more than 16 bytes using i2c_transfer() on nRF5340 DK

tozz88 — Tue, 12 Dec 2023 00:22:58 GMT

Great. this answers all my questions. So this ticket is closed in my mind. I'm new to this page so let me know if there is something I'm supposed to do to close this out.

thanks for your help

BobT

RE: Can't write more than 16 bytes using i2c_transfer() on nRF5340 DK

Kenneth — Mon, 11 Dec 2023 21:58:50 GMT

Glad to hear the problem is solved.

Regarding the "DMA" it simply means that the buffer need to be in RAM, not code flash.

Kenneth

RE: Can't write more than 16 bytes using i2c_transfer() on nRF5340 DK

tozz88 — Mon, 11 Dec 2023 20:44:10 GMT

Great. Thanks for your help. I already have an overlay file so adding the following to my &i2c1 entry did the trick:

zephyr,concat-buf-size = <514>;

The code from my original post works for arbitrary sizes up to 512 bytes.

However, I wanted to look into this more as I may be simply delaying the copy step to the driver's code if the buffer I supply isn't accessible to DMA. How do I allocate my buffers to ensure they are accessible to the DMA engine?

thanks.

RE: Can't write more than 16 bytes using i2c_transfer() on nRF5340 DK

Kenneth — Mon, 11 Dec 2023 10:53:08 GMT

Hello,

It looks to be a few things that can cause this:
if statement: https://github.com/zephyrproject-rtos/zephyr/blob/zephyr-v3.5.0/drivers/i2c/i2c_nrfx_twim.c#L92
error code: https://github.com/zephyrproject-rtos/zephyr/blob/zephyr-v3.5.0/drivers/i2c/i2c_nrfx_twim.c#L103

Not entirely sure which is kicking in here. Hopefully you can set a breakpoint here to find exactly what is causing that error code.

Kenneth