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CC2650STK: PDM Driver problem on sensortag 2650 (cc2650stk)

Alex Stevenson
Prodigy 90 points
Part Number: CC2650STK
Other Parts Discussed in Thread: CC2650RC, CC2650

Hi,

I'm currently working on a project in which we need to do a simple process on microphone recorded voice. We require various low power on-board sensor, so we have focused on sensortag 2650 (cc2650stk).

I've read (or think that read) about all forum threads regartding the sensortag microphone . As I know, sensortag 2650 remote control kit (cc2650rc) fully supports the microphone functionality; but we are very determined to find a solution to use microphone recorded voice locally on the sensortag.

I've found an example code with the name of "sensortag_audio_cc2650". I added UART write and read capability with the example code and send the data using Debugger Devpack UART port to a PC. Based on my gathered information, the PDM driver converts PDM data received from the microphone to PCM with a sampling rate of 16000Hz and 16-bit sample.

I tried to investigate the captured raw data with audacity. Unfortunately, the result was only some noise that has very little similarity to the real voice that I had made.

I was wondering if there are some body can help me to complete the test procedure, give me a thorough guide or any other suggestion. The main question is that "is there any serious problems preventing cc2650stk from having a functional microphone? Why have TI experts released the functionality for cc2650rc, not cc2650stk?".

Note that we don't need to send any voice over BLE and only wants to temporarily record the voice and do some simple process on it.


Thanks in advance.

  • 0
    TI__Guru 56215 points
    Hi,

    The sensortag audio project should work out of box as it's the same PDM driver and same microphone as the one on the CC2650RC.
    Here is an application note we have provided for the voice solution from TI
    www.ti.com/.../swra506

    What do you mean by raw data? You meant the uncompressed data?
    Can you try to use sine wave generated from audacity with frequency =440Hz and check the PCM data(tempPcmBuf) from the following function in PDMCC26XX.c,
    pdm2pcm16k(bufferRequest.bufferIn, decimationState, object->decimationFilter, (int16_t *)&tempPcmBuf);
    You should be able to see almost 1 period of sine wave. If not, then there might be something wrong with the mic.