How to get die temperature on NRF52832 using Zephyr

[Christian Holland]

I'm trying to get a temperature reading from the on-chip temperature sensor on the NRF52832 - I know it is not a very accurate sensor but I still want to use it. I found a very cohesive example of how to do this using the nRF SDK:

nRF5_SDK_15.0.0_a53641a/examples/peripheral/temperature

But I'd now like to implement this in Zephyr - has anyone got any examples of this working? I guess it'd be as simple as referencing the nrf_temp.h library that the example uses in order to get the necessary functions?

Any pointers would be greatly appreciated

Thanks

[Simonr]

Hi

Nordic contributes device support to the Zephyr open source project and can recommend it as a solution, though we do not offer technical support for Zephyr RTOS on nRF52 today. I am sorry, but we don't offer technical support for the Zephyr RTOS on nRF52 as of yet.

Best regards,

Simon

[David]

Are there any news on this topic? I would be interested in the answer to the original question

Thanks

[Christian Holland]

Hi mate, I struggled with this one so I'll help you out - this is how I did it in the end:

static int read_temperature(struct device *temp_dev,

    struct sensor_value *float_val) {

  const char *name = temp_dev->name;

  struct sensor_value temp_val;

  int ret;

  ret = sensor_sample_fetch(temp_dev);

  if (ret) {

    printk("%s: I/O error: %d", name, ret);

    return ret;

  }

  ret = sensor_channel_get(temp_dev, SENSOR_CHAN_DIE_TEMP, &temp_val);

  if (ret) {

    printk("%s: can't get data: %d", name, ret);

    return ret;

  }

  //printk("%s: read %d.%d C\n", name, temp_val.val1, temp_val.val2);

  float_val->val1 = temp_val.val1;

  float_val->val2 = temp_val.val2;

  generic_data[3] = temp_val.val1;

  return 0;

}

[David]

Hi Christian,

Thank you for the fast reply. Could you please tell me how to populate struct device* in your function call?

I found another example (installed with nRF Connect SDK in \ncs\v1.5.0\zephyr\samples\sensor\thermometer) that is quite similar to your code. Unfortunately, the following initialisation returns an error

temp_dev = device_get_binding("TEMP_0");

Best regards

David

[Christian Holland]

I assign temp_dev by using the CONFIG_TEMP_NRF5_NAME macro:

temp_dev = device_get_binding(CONFIG_TEMP_NRF5_NAME);

[David]

According to Zephyr documentation, the default value for CONFIG_TEMP_NRF5_NAME should be "TEMP_0", but that doesn't work for me. Could you check how it's expanded in your example?

Which chip / board do you use? I have an nRF52840-DK

What are the contents of your prj.conf file? Do I have to enable something more than CONFIG_SENSOR=y

[Christian Holland]

We've only been testing and using NRF52832 so i guess the binding could be different for the 528340 (although i wouldn't imagine so).

Try adding this to you prj.conf

CONFIG_TEMP_NRF5=y

[David]

Thank you for the hint. Unfortunately, CONFIG_TEMP_NRF5_NAME is still undefined.

However, CONFIG_HAS_HW_NRF_TEMP is set to 1, which means the hardware exists, but I can't figure out its name.

[Christian Holland]

Are you sure to include the sensor header file too?

#include <drivers/sensor.h>

If not I'm not sure what else, there's nothing else relevant in my prj.conf. Are you in the Zephyr Slack channel? They're normally quite helpful there.