RE: Formatting data send through saadc ble uart example

awneil — Mon, 22 Aug 2016 13:18:56 GMT

The UART profile is just a raw data profile, where you need to interpret data on the receiver side yourself

In other words, just like sending data over a real UART - hence the name!

RE: Formatting data send through saadc ble uart example

Stefan Birnir Sverrisson — Mon, 22 Aug 2016 11:47:03 GMT

Transfer over BLE is via bytes. You can put up to 20 bytes in each packet. If you have a SAADC value that is e.g. 10 bit value, you can fragment each value into two bytes, higher and lower byte, and then send the two bytes over BLE. If you wish to fill up a data packet with 20 bytes, each packet will contain 10 SAADC values with this method. The BLE peer device is responsible for defragment/decode the received data. An example of SAADC value fragmentation is available on Nordic's Github page. In this example in function saadc_callback, all data in the SAADC buffer is transmitted over BLE via NUS service. Before transmission, the data is fragmented. Maximum 10 samples are sent in each packet.
You can in theory send SAADC samples to any BLE profile you wish, but the data on the receiver side might not be interpreted correctly. The UART profile is just a raw data profile, where you need to interpret data on the receiver side yourself. A common example of SAADC use is to measure battery voltage, convert the measured voltage to battery level in % and send that value over BLE. An example of this is shown in this example, see the adc_event_handler function. The battery level value can be received with e.g. nRFToolbox HRM app.

To receive BLE data on PC, you need BLE device, e.g. BLE dongle. It can not be traditional Bluetooth dongle as that implements Bluetooth classic protocols. Bluetooth classic and Bluetooth low energy (BLE) are not compatible.