Changing the bitrate for usb-cdc
Hey folks
I'm trying to change the bitrate of the usb-cdc. So far we've been using 115200 as a fix value. Now I need the possibility to run it also on 38400. I know it is possible to configure it that way on the netX, but then the device won't connect to my host, or rather, the host won't recognize the device. Is this a problem of the windows driver and can I really only run it on 115200 kBit/s?
That's what I did too. But not right from scratch. I have the connection running on 115k first, then by some input over this connection I try to reset it to the 38k, which does not seem to work...
It might also be that it is some other problem though, since the application i try to connect to with the 38k is not really transparent for me, meaning I don't know the communication there in detail. I just try to tunnel it to one of the UARTs.
Chris Frickel
Hilscher
Hi HP,
The usb-cdc demo uses the bitrate only to reply to status requests. Windows is kind of suspicious and asks the device after a bitrate change if it really accepted the new value.
Devices like a USB-to-UART converter use the bitrate to configure the UART. However this will not affect the USB connection. The transfer will of course block if the UARTs fifo is full, but it will never be slowed down just because of the bitrate.
The usb-cdc demo is just a simple loop device with no real UART. It will transfer data at the same speed, no matter which bitrate you set.
That's strange. I changed the default bitrate in usb_requests_cdc.c, line 38 to 38400 and it still connects. What did you change?