Questions on the temperature sensor tutorial (temp conversion and decimal numbers)

RE: Questions on the temperature sensor tutorial (temp conversion and decimal numbers)

MartinBL — Tue, 05 Apr 2016 14:47:55 GMT

Generally speaking there are no restrictions on how you represent your value itself, if that is what you are asking. The Bluetooth SIG defined services and characteristics might be a bit confusing in the beginning. It might sound like you have to comply with these definitions always. But the deal with those is that if you are making e.g. a heart rate monitor belt then you can use these predefined standards so that all HRM applications for smart phones, for example, knows how to interpret the data. However, you are completely free to make whatever application you can imagine and represent your data however you want.

RE: Questions on the temperature sensor tutorial (temp conversion and decimal numbers)

Revo — Tue, 05 Apr 2016 13:43:48 GMT

Thank you very much, you can close the question! I'll be asking soon for other applications!

Edit: just to know for my future application, if i want to transmit the values of a sensor connected to the ADC (i convert the analog signal in digital, then send it bi BLE to a pc), there is a particular protocol to represent it on the pc or i just have to transimt for example the values returned in the ADC register?

RE: Questions on the temperature sensor tutorial (temp conversion and decimal numbers)

MartinBL — Tue, 05 Apr 2016 13:28:26 GMT

No worries. Unfortunately the MCP for PC cannot show you the decimal value. It will only show you the hex string. What you can do is to look at the ble_app_hts example in the SDK (hts = Health Thermometer Service). In this example you will see how to represent a temperature value in compliance with the Bluetooth SIG defined temperature measurement characteristic. When you have a temperature characteristic configured correctly you can use MCP for Android or iPhone to see the decimal values. Just enable "Parse known characteristics" in the settings menu and MCP will format the numbers for you. Note that MCP for phones only parses the values for known Bluetooth SIG defined characteristics. So it won't, e.g., parse the custom values we use in the tutorial.

RE: Questions on the temperature sensor tutorial (temp conversion and decimal numbers)

Revo — Tue, 05 Apr 2016 11:58:15 GMT

Great, thanks! And about getting the value in decimal instead of hexadecimal, on the control panel? Sorry for bothering!

RE: Questions on the temperature sensor tutorial (temp conversion and decimal numbers)

MartinBL — Tue, 05 Apr 2016 11:43:28 GMT

The result of the sd_temp_get() function is the nRF5 die temperature in 0.25 degrees celsius as documented here. So to get the real temperature you would have to divide the value by 4. Then you can convert it to fahrenheit by multiplying the temperature by 1.8 and finally add 32.

Bluetooth SIG has also defined a Temperature Measurement Characteristic with a standard way of representing the temperature. However, to make it simple and to show how to use vendor specific UUIDs I chose to do it differently and leave it up to the user to handle the conversion and representation.

I should probably have made this clearer in the tutorial and I will try to get it updated.