Our little USB interfaced thing is doing something else that I don't understand.
We use an LPC1768 to manage DACS and stuff. It has a USB interface, which we program such that it enumerates as a serial port. Sometimes, when we talk from a PC to the box, we get extra junk characters in the ascii data coming back from our box. This happens with Windows and Linux, using standard terminal programs or our own test programs.
There is a baud rate parameter in the ARM usb driver, and we set that to 115K baud and compiled the app. Turns out that the software running on the PC has to have its baud rate set high, 38K or more, or we get the garbles. A serial port opened at, say, 9600 has the junk characters.
What's weird is that, to me, the baud rate shouldn't matter. There is no actual serial data anywhere in the system.
I wonder if the OS attempts to throttle data into applications or something, based on the fake declared baud rate. But why *extra* junk characters?