USB isochronous bandwidth problem
Posted: Tue Sep 27, 2016 4:20 pm
Hi,
I'm using a STM32L4 as an USB audio device (with ST-HAL library).
My program works fine when I use a small number of audio channels but stops working when I increase it.
I suspected some bandwidth problem, so I opened wireshark to check USB traffic between the computer and my device. But I'm having trouble to understand what wireshark tells me.
From what I've read, host and device exchange one USB isochronous data frame every 1ms. And a frame is composed of 1 data packet.
But with wireshark, I see 9 packets of data in 1 data frame.
If you look at the capture below, the host is sending a huge data frame (>3kbytes) to the device.
Did I misunderstand how USB isochronous works ? Why am I seeing so much data packet in one frame ?
Thanks for your help
I'm using a STM32L4 as an USB audio device (with ST-HAL library).
My program works fine when I use a small number of audio channels but stops working when I increase it.
I suspected some bandwidth problem, so I opened wireshark to check USB traffic between the computer and my device. But I'm having trouble to understand what wireshark tells me.
From what I've read, host and device exchange one USB isochronous data frame every 1ms. And a frame is composed of 1 data packet.
But with wireshark, I see 9 packets of data in 1 data frame.
If you look at the capture below, the host is sending a huge data frame (>3kbytes) to the device.
Did I misunderstand how USB isochronous works ? Why am I seeing so much data packet in one frame ?
Thanks for your help