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SAM4s bootloader not responding via usb

Posted: Sun Nov 06, 2016 1:26 pm
by talanfree
Hello,
I am trying to communicate with sam4s on my custom board with simple commands given in section 24.5 in datasheet. Bootloader returns answer when is connected via UART. But when when i open terminal and try the same commands when connected to usb it doesn't return anything. USB is successfully enumerated and recognized as ttyACM0. I am running Ubuntu 15.10. Where am getting wrong?

Re: SAM4s bootloader not responding via usb

Posted: Sun Nov 06, 2016 10:37 pm
by tsvoipio
Check your master clock. An UART is much more tolerant toward inexact or varying clock frequency than USB.

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-TV

Re: SAM4s bootloader not responding via usb

Posted: Mon Nov 07, 2016 9:36 am
by talanfree
I am using external clock on XIN pin 12Mhz oscillator from TXC. I checked with a scope. It looks fine.
When USB is attached i can't communicate via UART. I guess it is switched correctly to USB.

Re: SAM4s bootloader not responding via usb

Posted: Tue Nov 08, 2016 9:32 pm
by talanfree
I've success with communication through USB. The solution is described in atmel
knowledge base
http://atmel.force.com/support/articles ... -ubuntu-PC

Does somebody know why reinitialize usb driver is needed?