I am setting up an Arduino to collect temperature and pressure data, and I want to broadcast that data via bluetooth.

My question boils down to what allocated UUID is best for my characteristic, and I think it would be great if that UUID specified the unit.

On BlueTooth Sig's website there is a pdf file with a bunch of 'allocated' UUIDs of which there is a column called 'Allocation Type' and under that column there are two categories of interest 'GATT Unit' and 'GATT Characteristic and Object Type'.

The UUID '2A6E' is a GATT Characteristic and Object Type and it appears to be what most people use to define a temperature characteristic.

The UUID '27AC' is a GATT Unit and it describes/allocated for 'thermodynamic temperature (degree Fahrenheit)'.

I am wondering if I can use a GATT Unit UUID to declare my characteristics so that I also get to convey the unit along with the data.

The pdf file showing all the different allocated UUIDs can be found here: https://btprodspecificationrefs.blob.core.windows.net/assigned-values/16-bit%20UUID%20Numbers%20Document.pdf

  • Have you checked file:///C:/Users/km72670/Downloads/GATT_Specification_Supplement_v5.pdf to see which one suits your use case better ? It appears that if you're sending a 2A6E, its Celcius. If 0x2A1C, you can send a bit that says C or F. See bluetooth.com/wp-content/uploads/Sitecore-Media-Library/Gatt/… Vs bluetooth.com/wp-content/uploads/Sitecore-Media-Library/Gatt/… Explore and experiment and let us know what you learned. Jan 12, 2022 at 17:57
  • You are correct in that 2A6E is in Celcius. I have a short bit of code doing that now. I tried using 2A1C to send farenheight, but I am running into problems with formating. I think this weekend I will do some more digging to figure out how to properly format values when accompanied with flags. The GATT Supplement was very helpful. Jan 18, 2022 at 13:10


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