RE: Setting up devicetree for I2C device that has address changed

Jared — Tue, 02 Jul 2024 12:42:10 GMT

Mike,

I think the best approach would be to use i2c_transfer() instead of i2c_transfer_dt(), since the former takes the address as an argument instead of using the address that is specified in the devicetree node.

regards

Jared

RE: Setting up devicetree for I2C device that has address changed

Mike Austin (LPI) — Mon, 01 Jul 2024 23:40:17 GMT

Hi Jared,

Sorry - I probably should have provided more detail.

I am trying to write some firmware that enables me to change the I2C address on a batch of these MLX90640 sensors, doing this one sensor at a time. I have about 20 in my application, and I need them all to be unique so I can access the info of each of them over the same I2C bus.

So, sequence is:

I connect one sensor up to my DK
Check that I can access it via is default address (0x33)
Take the updated address as input via UART
Reconfigure the sensor to that new I2C address
Then check that I can access it via the new address.
I then remove that sensor from the I2C bus, and connect up the next sensor
Then repeat steps 1-6 with the next sensor

So, I don't want to have to rebuild everything between steps 4-5 and 5-6.

I've not actually tried this approach as yet (still waiting for the sensors to arrive), but as I understand it, this code:

static const struct i2c_dt_spec mlx90640_i2c = I2C_DT_SPEC_GET(I2C0_NODE);

Will simply populate the values of the i2c_dt_spec structure with the device and addr info from the device tree. So, in theory, when I get to step 5, I just need up update the value of mlx90640_i2c.addr with the new address (e.g. 0x40) and I should then be able to read/write to it.

Does that sound like it will work?

Regards,

Mike

RE: Setting up devicetree for I2C device that has address changed

Jared — Mon, 01 Jul 2024 13:08:21 GMT

Hi there,

I'm not sure I understand the question. The device node label will be updated once you rebuild your project.

Are you getting any build errors?

Please elaborate on the question.

regards

Jared