AVR-CDC

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Total votes: 8

christian
Objective Development
Objective Development
Posts: 1428
Joined: Thu Nov 09, 2006 11:46 am

AVR-CDC

Postby christian » Mon Apr 09, 2007 1:01 pm

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Guest

Re: AVR-CDC

Postby Guest » Wed Feb 06, 2008 5:01 pm

This device implements a serial device that has at least two advantages compared to using an FT232 or similar:

* No special driver is necessary, Windows uses its supplied driver. For unknown reason, the user must supply a .INF file.

* The baudrate / parity / stopbit setting is totally transparent to the application; the user can select any baud rate, and the result is always the maximum USB speed. No hassle with garbage data when a wrong communication setting is used.

IMHO, this kind of interface tends to arise to an allround solution for a couple of microcontroller applications.

cz8pru

CDC ACM

Postby cz8pru » Tue Mar 04, 2008 7:18 pm

I try this project under Linux (kernel 2.6.17) and it doesn't work, but under Windows XP it works well. That's pity.

Can you help me with driver for linux?

email: cz8pru@seznam.cz

christian
Objective Development
Objective Development
Posts: 1428
Joined: Thu Nov 09, 2006 11:46 am

Postby christian » Wed Mar 05, 2008 4:27 pm

Linux does have a driver, but maybe you have not enabled the module when compiling the kernel. You need the cdc-acm module.

suriva.25

question about USB - CDC

Postby suriva.25 » Mon Sep 01, 2008 11:26 am

anybody have tested USB -CDC/Virtual COM port?
it's just half duplex or full duplex??

henni
Posts: 16
Joined: Mon Sep 08, 2008 4:17 pm

Re: question about USB - CDC

Postby henni » Mon Sep 08, 2008 4:27 pm

> anybody have tested USB -CDC/Virtual COM port?
> it's just half duplex or full duplex??
Full-duplex.
Therefore, RTS and CTS handshake cannot controlled by host driver, and appropriate handshake signaling must be done by AVRCDC if needed.

This AVRCDC does no handshake at all, and don't support modem status lines (DTR, DCD, RI, DSR) and no BREAK signaling in either direction.

I have written AVRCDC based firmware that (at least) fakes modem status lines and BREAK for a dedicated reason:
"http://www.tu-chemnitz.de/~heha/bastelecke/Rund um denPC/FunkUsb/"
Last edited by henni on Mon Sep 22, 2008 11:37 am, edited 1 time in total.

henni
Posts: 16
Joined: Mon Sep 08, 2008 4:17 pm

Re: CDC ACM

Postby henni » Mon Sep 08, 2008 4:30 pm

> I try this project under Linux (kernel 2.6.17) and it doesn't work,
> but under Windows XP it works well. That's pity.
>
> Can you help me with driver for linux?

Maybe you must somehow enable that Linux supports BULK pipes on low-speed devices.
Generally, Linux prohibits this feature because it's outside USB specification as it may consume too much bandwidth.


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