BLE real time data transmission nrf51 DK code

[carvalhn]

Hi Guys,

I need to implement real time streaming of accelerometer and gyro values from the nrf51 DK to either a desktop or android system. Could someone please help me on how to go about with this and if there are any desktop clients JAVA for reading data from the nrf51 board over BLE? Basically, I need to concentrate on data streaming and I need a data rate of 50kbps or so, is that achievable with nrf51? Also, are there any GATT profiles for accelrometer data because I couldnt find any

Thanks and Regards, Neil

[Kenneth]

The max throughput with ANT is 60kbps, however this is without re-transmissions, so achieving 50kbps is not realistic in the long run.

The max throughput with Gazell is up to 500kbps, however then you would require a nRFLU1P USB dongle on the PC side to also run Gazell, theoretically I guess you can then design this with either CDC or HID class for the nRF24LU1P (you might also use libusb, but not sure if that works with Android). It would require some work to get the nRF24LU1P firmware running, in addition you will need to create the application on the peripheral and OS, but technically possible, and likely the best solution in terms of throughput.

In terms of BLE the max throughput is up to 128kbps, however due to the way BLE will re-transmit; if a packet fails it will have to wait until next connection interval (min. 7.5ms) before it will re-transmit. Then the max throughput can reduce rapidly depending on interference in the system. You might be able to achieve 50kbps over time, but the latency can be very high (e.g.>100ms) in some scenarios.

Indepedant of what profile you choose to use to interface the data stream (HID, CDC, proprietary way...) the raw throughput will be the same for any BLE implementation really, given the connection parameters is the same, the difference will be the api mainly.

For a PC application using HID it should in theory work the same independant if it's USB or BLE that is the transport layer. Some resources to get started on a PC application using HID or BLE: msdn.microsoft.com/.../jj128407(v=vs.85).aspx code.msdn.microsoft.com/.../

In terms of source code to get started with the nRF51 or nRF24LU1P you need to look at the SDK's for each of the chips.