How can i send twi data(like accelerometer) by bluetooth to another Nordic?

[lorenzot98]

Good morning, i would want to develop a code in order to have a twi sensor(like an accelerometer) and communicate its data by Bluetooth to another board Nordic, or computer. Now i have two Nordic nrf52840. How can i solve this? Using NUS? And how? Thanks

[Jørgen Holmefjord]

Hi,

It is possible to send TWI sensor data using NUS, or you can create your own custom service/characteristics for sending the data, by following these tutorials:

• Bluetooth low energy Services
• Bluetooth low energy Characteristics

If you send the data through NUS as strings, the data will take more space than necessary, but you can send binary data through NUS as well if you want.

Best regards,
Jørgen

[lorenzot98]

Perfect thanks! Sorry if I use NUS service and i want to send accelerations, gyroscopes and temperature simultaneosly,  i have to work with the uart _event_handler by adding different ble_nus_data_send cases, doesn't it?  If instead I use service/characteristic method , must i create a single service and characteristic for every single data? Sorry because I'm not so familiar with BLE and now i will deepen with your tutorials thanks.

[Jørgen Holmefjord]

If you want to send different data types with NUS you will have to add some sort of tag or header along with the data in order for the receiver to be able to distinguish between the data transfers.

With custom services you can create a separate characteristics for each data type and the receiver will be able to match the received data with the service and characteristics handlers. This will become more clear when you work through the tutorials.

[lorenzot98]

Perfect, thanks for your answers!

Best Regards,

LT

[lorenzot98]

Good morning, I used NUS service and now I'm able to send data between master board and slave board. Now I have another problem: using a terminal emulator like Putty, i have particular characters instead of having numbers(coming from an ADC sampling). I suppose the problem is related to the encoding of the single data, maybe because it reads ASCII characters,doesn't it? How can i solve this problem? In particular, what could I add in the slave code in order to have printed number samples instead of these characters? Thanks

[Jørgen Holmefjord]

Correct, if you send the data as binary bytes, Putty will not be able to show the data, as it will try to decode it as ASCII. You can use sprintf in your application to convert the binary data to a string, either on the transmitter (will increase transferred data size) or on the receiver side. There also exists serial terminals that can show binary\hex data (e.g. Termite or Realterm).