I need to output a stream of binary data at a constant rate to a USB port. I am using Windows7, I can connect and send the data to the USB port but what I just can't control is the frequency at which the data is sent. Does anybody know any functions I can use so I can control the baud rate of data getting into a USB port?
Do I need to use a Real Time OS?
This seems like a really good article on the subject:
Embedded.com - An Introduction to USB Development
Sorry I'm not an expert at communicating through USB ports myself, but my guess is that it'd be hard to get a guaranteed data transfer rate if you're not on a real-time OS...simply because your subject to the scheduling of the operating system.
Can you say what kind of app your working on? Is constant rate 100% necessary?
[EDIT]
Shameless plug:
http://sine.ni.com/nips/cds/view/p/lang/en/nid/2381
[/EDIT]
The stream of data needs to be recognized by a device that expects data in a specific format and specific frequency so constant rate is absolutely necessary - up to a 3% deviation is acceptable.
Is there a way I can increase my driver/thread priority through my code so that the timing of the data won't be as suceptible to Windows scheduling?
PS: Thanks for the article!
No idea about Windows but on *nix systems, it's sort of
1. open() the USB device using its device file
2. create a structure object of type struct termios
3. call tcgetattr() to obtain the current port options
4. set the input baud rate with a call to cfsetispeed()
5. set the output baud rate with a call to cfsetospeed().
Hopefully you can find something similar on Windows
USB has no "baud rate." If you need data to be transmitted at a particular rate, then... transmit it at that rate. I'm not sure what your question is.
Code://try //{ if (a) do { f( b); } while(1); else do { f(!b); } while(1); //}
The USB will have a baud rate if it is hooked to a serial port interface, which is what I thought the op had in mind when s/he posted the question. Guess the op will have to clarify what's exactly goin' on.
