Streaming SAADC values over BLE at 1 ksps

[Ankush]

Hi ,

I am working on one application in which i need to stream the ADC values over BLE to the mobile App. This should happen at very high rate i.e. 1000 samples per seconds. I am using SAADC of nrf52 with 12 bit resolution.

Can it be possible and what are the parameters should I consider while doing this? Please help me to solve this issue. Kindly suggest any sample code or any important thread related to this.

[puz_md]

Hi Ankush,

while Bluetooth Smart was not designed for high bandwith data streaming, sending 1,5 KB/s (that would be your raw payload) or 2 KB/s (when sending 16 bit values) should be perfectly fine with the nRF52. The receiving side (your mobile app) should be abe to handle the data efficiently, though.

For the communication method, I suggest you use notifications (no handshaking, data packets may be lost) or indications (with handshaking). You may also want to take a look at the UART tunnel implementation provided by Nordic Semiconductor: Nordic UART Service. Probably this would be the easiest way to get your data to your mobile device (although I have not tested actual throughput of this service yet). A samle Central implementation (in your case, that would be the mobile device) can be found here.

Oh, and maybe you want to use SoftDevice S132 v3.0 which has recently been released and should provide higher throughput. If I understand correctly, your movile device will have to support Bluetooth 4.2 to take advantage of the improvements.

[Ankush]

Hi all,

First of all , thanks for your reply.Yes I am using Nordic UART service to send the data over standard NRF APP. Just for understanding I am sending live battery values over BLE. But it is little bit confusing for me that I am not getting how can I sample the data at 1000 sample per second using SAADC.

I am using APP TIMER to do this operation and using APP_TIMER_TICKS(1, APP_TIMER_PRESCALER) command to sample the data. If I am not wrong it will give sampling interval as 1 ms (1000 samples per seconds). But when i am running the code as soon as I enable notification, it will disconnect the operation and starts advertizing again.....Can you suggest me proper way of sampling analog data at 1ksps or above....