Implementation for (*i2c_callback_t) in Zephyr

[drumpros]

Hello there,

In the Zephyr docs i can see theres a typedef for i2c_callback_t but looking through the SDK, i cannot see a any uses for this type.

i am trying to create a callback for my successful/unsuccessful i2c operations, i have also tried using i2c_target_config and the i2c_target_register() function, but had no luck with callbacks.

is there a way to implement this i2c_callback_t? i am on Zephyr 3.2.99.

[Einarh]

Hello

Looking at the documentation I agree it looks like you're supposed to set it up using i2c_target_register().

It also seems to me like callbacks are only implemented for the I2C slave API, so if you're trying to set up these callbacks for a master device that might be why you're unsuccessful.

I would recommend asking about this on Zephyr's Discord forum:

https://www.zephyrproject.org/community/

Best regards,

Einar

[drumpros]

Hi, i have had no luck asking on the Zephyr community, i have also tried to set up a callback on a slave device  using target register but it returns -ENOSYS which happens 'If target mode is not implemented'. any ideas on how to fix this issue?

Thanks

[Sigurd]

Looks like you need to use a transfer_cb function for use with the callback. See https://github.com/nrfconnect/sdk-zephyr/blob/v3.3.99-ncs1/include/zephyr/drivers/i2c.h#L741

If the driver does not implement this function, you will get the ENOSYS error (Function not implemented).

	if (api->transfer_cb == NULL) {
		return -ENOSYS;
	}

The underlaying nrf i2c driver does not implement this API function.

https://github.com/nrfconnect/sdk-zephyr/blob/v3.3.99-ncs1/drivers/i2c/i2c_nrfx_twim.c#L298

It has it has configure, transfer and recover_bus

[andrew_alloy]

I followed the Zephyr docs to implement this today and then got -ENOSYS and found that the Nordic drivers don't support it even though the functionality was merged into Zephyr's main branch on Aug 11, 2022.  Sigurd Do you know when this will be implemented in Nordic's drivers?

[Sigurd]

andrew_alloy said:

Do you know when this will be implemented in Nordic's drivers?

Not sure. I have now flagged this as a feature request.