USB CDC on custom board doesn't work

Discussion around product based on ARM Cortex M4 core.

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Posts: 4
Joined: Tue Sep 24, 2013 2:29 pm

USB CDC on custom board doesn't work

Wed Sep 25, 2013 9:53 am

Hi all,

I have custom board based on ATSAM4SA16BA-AU with 16 MHz oscillator. I can't startup USB CDC service on it.

I took SAM4S-XPLD board (based on ATSAM4S16C), build USB CDC example project and it works. Then I change target MCU in that example project to ATSAM4SA16B and download on my custom board using j-link. On attaching board to PC I see "unknown device" in Device manager. What I already tried:

1. I changed oscillator speed in the project from 12MHz to 16MHz.

2. I checked USB+ and USB- lines on board. No schematics problems found (they have 20 ohm resistors as in evaluation board)

What should I check?
Posts: 27
Joined: Wed Jun 06, 2012 2:08 pm

Re: USB CDC on custom board doesn't work

Wed Sep 25, 2013 2:19 pm

Make sure that the USB clock has the right frequency. I don't know these processors, but there could be a difference in programming their usb clocks (clk source, dividers, timers, ...).

Check how the USB connection is detected (VBUS). On a GPIO input, or dedicated pin, how it is set up and handled (GPIO setup, interrupt, polling, ...).

Your USB lib may also have various "#define ...." to be modified according to the processor used and hardware.

Posts: 1
Joined: Thu Jan 12, 2017 5:33 pm

Re: USB CDC on custom board doesn't work

Fri Jan 13, 2017 12:20 pm

Any solution to this problem?
Posts: 68
Joined: Mon Jan 26, 2015 2:33 pm

Re: USB CDC on custom board doesn't work

Fri Aug 04, 2017 9:09 am

paolo_sanchez wrote:Any solution to this problem?
Ha ha I jumped in here based on the date, and then realised the OP was done quite some time ago. Got me paolo_sanchez.

We have implemented USB on a custom board using a SAM4S8B, and got it working... with some work on the I/O lines. We do have a SAM4-XPLAINED, but only used it for testing of the PDC setup for UART's and SPI, so cannot comment on any USB examples. However, we just used the ASF example code, and configured the clocks. Thereafter it's a serial UART.

Anything specific that is tripping you up?

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