Bluetooth specifications

To connect to the calibration part of the Hamilton, you need to connect to service with UUID 0x1337 that contains two characteristics:

CharacteristicID
Write0x3000
Notification0x5000

The calibration uses the calibration protocol defined here

Data processing

nRF forwards the data received as a string on the Write characteristic and forwards it as a packet with an item ID of 666 to the STM, where it gets processed.

When sending data, nRF receives a packet that contains only one item (with an id of 666), which contains a byte array (an array of ASCII characters), which gets extracted and forwarded through bluetooth notification.