Setting up a MP8862 with i2c

[J Boumans]

Hey devs,

I'm trying to get the i2c interface to work with the MP8862. I followed the TWIS driver guide to get started and in there everything worked.

Now I wanted to setup the sensor and thus changed my overlay file to:

&i2c1{
	compatible="nordic,nrf-twim";
	status = "okay";
	sda-pin = <30>;
	scl-pin = <31>;
	clock-frequency = <I2C_BITRATE_STANDARD>;

	twis_device1:MP8862@6b {
		status = "okay";
		label = "MP8862";
		reg = <0x6b>;
	};
};

I just used the i2c to send the reset command and would want to try to poll it, but that gives me following error: from.

I2C device 1: MP8862
I2C Master: Slave ADDR: 0x6b SCL: 31, SDA: 30, CLK(Hz): 100000

[00:00:01.270,660] <err> i2c_nrfx_twim: Error 0x0BAE0001 occurred for message 0
[00:00:02.270,843] <err> i2c_nrfx_twim: Error 0x0BAE0001 occurred for message 0
[00:00:03.271,026] <err> i2c_nrfx_twim: Error 0x0BAE0001 occurred for message 0
[00:00:04.271,240] <err> i2c_nrfx_twim: Error 0x0BAE0001 occurred for message 0
[00:00:05.271,423] <err> i2c_nrfx_twim: Error 0x0BAE0001 occurred for message 0
[00:00:06.271,636] <err> i2c_nrfx_twim: Error 0x0BAE0001 occurred for message 0

I could find it was an internal error, but could not find where it was coming. 

Hope you can help!

Joep

[Simon]

I guess it is the function i2c_write() you're running that is causing it to fault. That function should be coupled with i2c_nrfx_twim_transfer(), which will run nrfx_twim_xfer(). The function nrfx_twim_xfer() has the following return types:

https://github.com/nrfconnect/sdk-hal_nordic/blob/8f013ea950f41bf69b18bf688bfb0dd80a3fdc44/nrfx/drivers/include/nrfx_twim.h#L299-L306

If you take a look at modules\hal\nordic\nrfx\drivers\nrfx_errors.h, the error 0x0BAE0001 evaluates to NRFX_ERROR_DRV_TWI_ERR_ANACK. That error means that a NACK is received after sending the address, so the address you're sending is not acknowledge by the MP8862. I can see that you have set the address to 0x6b, is that the correct one? Doublecheck the datasheet, and maybe check the lines using a logic analyzer to see what is actually sent.

Best regards,

Simon

[J Boumans]

I tried to used the i2c_nrfx_twim_transfer() to send the data, but it is undefined. I included nrfx_twim.h and enabled it in the conf with 

config_nrfx_twim=y

.

How should I include it?

Indeed the address for my testing setup was off. I did not yet have time to test this with the correct setup.

[Simon]

I would not recommend you to mix the Zephyr layer and the nrfx layer (the Zephyr layer will use the nrfx layers under the hood). The zephyr api will get information about the I2C configuration from dts (e.g. overlay) and Kconfig (e.g. prj.conf), and the nrfx layer will not. I have gone more into details about the NRFX/Zephyr layer in this answer: https://devzone.nordicsemi.com/f/nordic-q-a/70627/what-s-the-official-way-to-implement-a-simple-peripheral-spi-i2c-etc-with-ncs/290247#290247 

By the way, here is a sample that demonstrates how to use the NRFX API: https://github.com/nrfconnect/sdk-zephyr/tree/d9cc0d37bf45a544ccc7bb0df159d470b836724d/samples/boards/nrf/nrfx  

Best regards,

Simon