Output from waveplayer suddenly shortened

alastair

Hi there,

I have code that sends a white noise masking sound from Ch1 of the Waveplayer to a speaker, and a stimulus wave from Ch2 to a piezo. They are both 20000 samples and the Waveplayer sampling rate is set to 20kHz. I use Triggermode ON and LoadSerialMessages to send the waveforms. Everything was running fine for several days and then all of a sudden the Bpod seemed to delay a little bit while some trials were running and now the waveforms are cut short every time I play anything. They are always cut off at around 50 ms in length. Nothing changed in the code so it seems to be more of a hardware issue. It is still cut off if I make the signals longer.

I have tried changing serial ports, changing Waveplayers, and changing the Bpod state machine but the problem persists with the different equipment. Could it be some sort of timing update issue? I don't understand how it can persist when I change out the hardware unless there is default setting I am missing? Any help you could give me would be greatly appreciated.

Josh

Hello Alastair,

The first 1,280 samples of each waveform are stored in a RAM buffer on the microcontroller. When a waveform is played, these initial samples are read out to the DAC while the microSD read operation is initialized.

If your microSD card failed in a way that returns 0's instead of data, the samples in RAM buffer would still play, lasting 64ms at 20kHz.

It seems unlikely (yet possible) that the microSD cards in both of your analog modules have failed. We had a series of unfortunate experiences with unreliable vendors of SanDisk Industrial microSD cards, before we found a reliable source here.

If you're able to find one in the lab, please try swapping the card to determine whether that is the issue. You'll need a card with at least 8GB, and U1 rating, ideally SanDisk brand. To open the enclosure, press on the lid overhang and feed it through the horizontal slot.

Please let me know if this works!

Thanks,
Josh