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USB Full-speed comms?

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USB Full-speed comms?

By roach
-  Mon Jul 10, 2006 5:42 am #15622
I'm trying to interface with an LPC2138 over USB. Basically what I want is the equivalent of a virtual COM port (like the cp210x, or FTDI chips), but with the transfer rates of USB Full-speed (supported by the mcu).

Surely I can't be the first person to want to do this, but there is a pretty sever shortage of source code samples out there, so I wondered if anyone here would have any links or tips they'd be willing to share.

I know I'll need the following:

1) an LPC20XX full-speed USB stack. (thinking of using LPCUSB, here)
2) a device driver for windows that can talk to the device, preferrably open-source.

any ideas?

By SOI_Sentinel
-  Mon Jul 10, 2006 8:10 am #15630
Hmmm... if your LPC firmware you found mimics the Communication Device Class, it'll be recognized by any modern OS as a serial port. I've looked at this from a Microchip USB based system this weekend, actually. It might have that baud rate limitation you're seeing (probably 921Kbps?), though.

Hmmm...

Other than a custom solution, maybe you can get it to masquerade as a Mass Storage device?
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By roach
-  Mon Jul 10, 2006 12:04 pm #15642
SOI_Sentinel wrote:Hmmm... if your LPC firmware you found mimics the Communication Device Class, it'll be recognized by any modern OS as a serial port. I've looked at this from a Microchip USB based system this weekend, actually. It might have that baud rate limitation you're seeing (probably 921Kbps?), though.

Hmmm...

Other than a custom solution, maybe you can get it to masquerade as a Mass Storage device?
Yeah, all the Virtual COM port drivers I've seen have a baud rate cap at about 115Kbps. 921 would be sweet by comparison, but still not the 12Mbps I'm looking for. I thought about doing mass-storage device, but then all operations would have to be through the file system (loading firmware, uploading/downloading files, getting device information, etc.) This is not really convenient for me, but if it's the only full-speed solution I can find, I'll probably go with that.

By Kuroi Kenjin
-  Tue Jul 11, 2006 4:33 am #15660
well it'll be good for the uploading/downloading files. For the upgrading and device information you can take a lesson from Linux's /proc file. That is a virtual file with process information and it doesn't actually exist on the hard drive. You can do something like that.
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