USB not working - SOLVED

Discussion around products based on ARM Cortex-A5 core.

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bjornhi2
Posts: 8
Joined: Mon Sep 08, 2014 12:00 pm

USB not working - SOLVED

Fri Feb 20, 2015 2:18 pm

Hi,

We have been able to get more or less all functions of the ATSAMA5D31 working except the USB client port. (Which is somewhat irritating as first programming over JTAG is soo much slower…) 

The normal scenario is that the computer says the connected USB unit is not recognized. Rarely we get to the next step and it is shown as a COM-port. But never been able to use SAM-BA to program it. 
What we tried so far is:
  1. 1. Replace the 12 MHz crystal with 4-5 different alternatives from other suppliers.
  • 2. Modify the load capacitors on the crystal with different values. (Manually measured the frequency to be spot-on 12 Mhz.)
  • 3. Soldered a USB cable directly to vias very close to the processor. (Signal wires on PCB were cut to avoid stubs.)
  • 4. Added caps to power nets VDDUTMIC and VDDUTMII.
None of above does help. As shown in the schematics (http://1drv.ms/1AchZq5) the connection is very simple, not much that can be wrong. 

Open for any tips or ideas. Helpful just to know if anyone are successfully using the USB port on ATSAMA5D31.

Kind regards
Bjorn
Last edited by bjornhi2 on Fri Mar 06, 2015 10:43 am, edited 1 time in total.
stephanhd
Posts: 3
Joined: Sat Jan 17, 2015 8:27 pm

Re: USB not working

Sun Feb 22, 2015 3:58 pm

Hi Björn,


did you found a/the solution? We are struggeling with the same problem (but different CPU==SAM4S16B). Enumeration always failing - no VID/PID from device.



We run Rserial from 33 to 10Oohm, tried a bunch of crystals (12MHz) - CPU is working like charm - except the USB thing (we have several own boards at the start). Best, Stephan
bjornhi2
Posts: 8
Joined: Mon Sep 08, 2014 12:00 pm

Re: USB not working

Mon Feb 23, 2015 8:04 am

stephanhd wrote:Hi Björn,


did you found a/the solution? We are struggeling with the same problem (but different CPU==SAM4S16B). Enumeration always failing - no VID/PID from device.



We run Rserial from 33 to 10Oohm, tried a bunch of crystals (12MHz) - CPU is working like charm - except the USB thing (we have several own boards at the start). Best, Stephan
Hi Stephan,
Unfortunately no working solution yet. Will update post if successful.

/B
bjornhi2
Posts: 8
Joined: Mon Sep 08, 2014 12:00 pm

Re: USB not working

Thu Mar 05, 2015 3:45 pm

Update. Had by mistake connected the VBG pin to 10 nF instead of 10 pF. Changing to 10 pF helped when Linux is running on the processor. USB is working fine in that case. But still issues with SAM-BA. There is a long delay (10-15) seconds and then error "A request for the USB device descriptor failed". 

Any ideas to why normal usage of USB works fine but not SAM-BA?

Kind regards,
Bjorn
stephanhd
Posts: 3
Joined: Sat Jan 17, 2015 8:27 pm

Re: USB not working

Thu Mar 05, 2015 5:09 pm

Hi Björn,

since the SAM4S does not have a VBG it must be something different for us.

But we are (few minutes ago) one step further:
Same board but different CPU.
We had the feeling that something is wrong with this specific batch of CPUs; not moved to another batch and voila: it works like designed from start right away :)

We have a case open at ATMEL; lets see what they could do...

Best and good luck for your project!
Stephan
bjornhi2
Posts: 8
Joined: Mon Sep 08, 2014 12:00 pm

Re: USB not working - SOLVED

Fri Mar 06, 2015 10:31 am

Problem solved!

Apart from the wrong value on the cap on VBG we had another issue. On pin debug RXD pin we had a 10k pull-down. Changed it to a 56k 3.3V pull-up. That made USB and SAM-BA work as normal. By some reason SAM-BA freezes and disables the USB interface otherwise. 

Tricky problem. Hope this thread can be useful for someone else.

Kind regards,
Bjorn

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