USB CDC ACM data transfer

[Petar02]

Hello,

I have a problem with a tablet that i was planning on using (Xiaomi Pad Pro), my device (nrf25840 dk) is sending data in packets, 4000bytes per packet and its sending 77 packets per second. And its working for every other mobile device including some xiaomi s, but for this tablet somehow the speed is 2 times slower. on the nrf side, the data is processed at the set speed but when data needs to be send its 2 times slower that set speed, so there is no missing data on tablet side. My question is there a way to force on the nrf side to set a seed, because its seems that tablet slows down communication with nrf and data transfer.

Thanks in advence.

Petar.

[Kenneth]

Hi,

As a USB device I don't think it's much that can be done no, I am still a bit interested in how this 77 packet/s is implemented, so just to make sure I don't misunderstand: If you keep 4000bytes, but slowly reduce from 77 packets/s (308kBps) to e.g. 70 (280kBps) or 60 (240kBps), does that work, or you have to go all the way down to 45 packet/s (180kBps).

Kenneth

[Petar02]

Hi,

I didn't actually try to reduce the number of packets, because my adc runs at 153kHz and I just collect data from the adc output into ping pong buffers and send them using the nrf USB CDC ACM function to send data. sdk-zephyr/samples/subsys/usb/cdc_acm/src/main.c at v4.0.99-ncs1-2 · nrfconnect/sdk-zephyr. It goes on its own down to 45 packets just for that one tablet haha, but stil adc running on 153kHz.