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C5535 eZdsp stereo recording

Adrien Beraud
Prodigy 70 points
Other Parts Discussed in Thread: TMS320C5535

Hi,

I'm trying to make audio recording work on the TMS320C5535 eZdsp, starting from the Connected Audio Framework (CAF).

Since the mic-bias is only wired to the left channel, I use a self-powered microphone and disabled the micbias.
Until now things are going fine, and after enabling ENABLE_STEREO_RECORD, the PC receives a 16kHz stereo audio stream.

However I have issues with the way the stream is transmitted to the PC by USB.
The PC receives audio samples in the wrong order.

I first tried to modify appRecordAudio() in app_usbac.c by commenting out *leftDataBuf++ = 2*dataLength
This helped but did not fixed everything. My current issue is that about 20 times a sec, the left and right channel are reversed during 17 samples.

To highlight the issue I set the record data to constant values (different for left and right).
These two screen-shots show the result: the two channels are reversed from time to time.

  • 0
    Prodigy 70 points

    Hi,

    I finally fixed this issue. I'm not entirely sure but the problem seemed to be that the usb message length was computed using the number of samples received from i2s.

    It was almost always 32 "false" 16bits bytes (64 true bytes), ie 16 stereo 16bit samples, but sometimes it was 34 bytes - ie 17 stereo samples - and this apparently caused the message to be shifted and the right and left channels to be reversed for this usb message.

    I harcoded a message length of 32 in app_usb.c line 1268 and the issue was solved.

  • 0 in reply to Adrien Beraud
    Prodigy 10 points
    HI Adrien Beraud：
    I have a same problem of stereo recording . But i can not slove it. can you help me? I use the veision of Connected Audio Framework (CAF) is v02.00.02.04 . In this version, line 1268 do not have any content.