Xcore 200 Issue with 3 Bytes per sub slot
Posted: Fri Oct 19, 2018 10:04 am
Hi,
I'm working with the xCore 200 MC Audio dev kit and the reference software. As mentioned in this topic, we want to use 40 USB channels. To get this amount of channel, we need to use 3 Bytes per sub slot.
First, I tried 3 Bytes per sub slot for only 32 channels to validate the use of 3 Bytes per sub slot.
And I got a problem on the PLAY path (Computer > USB > XMOS). The data output is hashed periodically (cf the output below where the input is a sawtooth)
The period of this hashing is 56 samples at 48kHz (1.17 ms), so there is 56 samples of zero and then 56 samples of data etc...
The time taken for each frame (one sample for all the channels) is below the maximum time per sample (20.8 us at 48 kHz). However, the time taken for each frame varies periodically.
I didn't modify the Software Reference, except the VENDOR_ID/DEVICE_ID/USB descriptors to work with our Theysicon driver and the define to use 3 Bytes per sub slot.
For 30 channels 3 Bytes per sub slot or 32 channels 4 Bytes per sub slot, everything works fine. However for 40 channels we need to use 3 Bytes per sub slot (and so we get the problem).
Thanks for any help. I created this new topic (rather than continue the old one) because it is linked directly to the reference Software, which is announced to work at 32 channels.
Marc
I'm working with the xCore 200 MC Audio dev kit and the reference software. As mentioned in this topic, we want to use 40 USB channels. To get this amount of channel, we need to use 3 Bytes per sub slot.
First, I tried 3 Bytes per sub slot for only 32 channels to validate the use of 3 Bytes per sub slot.
And I got a problem on the PLAY path (Computer > USB > XMOS). The data output is hashed periodically (cf the output below where the input is a sawtooth)
The period of this hashing is 56 samples at 48kHz (1.17 ms), so there is 56 samples of zero and then 56 samples of data etc...
The time taken for each frame (one sample for all the channels) is below the maximum time per sample (20.8 us at 48 kHz). However, the time taken for each frame varies periodically.
I didn't modify the Software Reference, except the VENDOR_ID/DEVICE_ID/USB descriptors to work with our Theysicon driver and the define to use 3 Bytes per sub slot.
For 30 channels 3 Bytes per sub slot or 32 channels 4 Bytes per sub slot, everything works fine. However for 40 channels we need to use 3 Bytes per sub slot (and so we get the problem).
Thanks for any help. I created this new topic (rather than continue the old one) because it is linked directly to the reference Software, which is announced to work at 32 channels.
Marc