Hi,

I am using this board from Olimex:
http://www.olimex.com/dev/sam7-h256.html
My problem is that this board has a resistor pull-up on DDP, and all the examples I have found for starting some USB communication handle DDP pullup by switching on a mosfet (this is also the recommended mode in the datasheet).
It does not work also (no interrupts received) if I connect the board directly (I wonder how the Sam-Ba firmware works here). How should the usual AT91C_UDP_ENDBUSRES be handled in this case? Is there a workaround for this?
Should I directly consider that this already happened upon reset and continue setting up the endpoint? I have no more ideas...

Thanks,
Costa

Hi Costa

A board with a direct pull-up will cause the PC to try to enumerate as soon as the board is connected (powered via the USB).

This is not a problem if there is code running on the board which handles the USB connection (eg. the USB boot loader when the NV bit to start application is not programmed, or the FLASH is fully erased, or user code is available with the necessary functionality).

Where this won't work is when there is a debugger being used and the debugger must first load the program. In this case the PC will not detect the device and enumeration will fail and the only way to start again is to unplug the power, which will subsequently fail again when connected).

The same problem is true on ATMEL's EVB. The way around this is to power the board directly with 5V (external power supply), load the program with the debugger and, once it is running, connect the USB cable to the PC. Olimex's board for the SAM7X does have a switch which allows this to be controlled in SW but the header that you have is obviously made as simple as possible and so is not so suitable for USB development without a little more effort.

Regards

Mark

www.uTasker.com

Hi Mark,

Thanks a lot!
I was convinced that I could somehow get it started without a separate power supply, but now I have added one (in parallel with the USB power, which is not so good, but I didn't burn anything so far, and I have no other options than cutting tracks, which is not good either). It works. I still have to see what happens with only USB as power source, but I'll do that *after* I get it all done.

Thanks again & Regards,
Costa