Re: [OpenOCD-user] SWD transport for sysfsgpio

[Jean-Christian de R. <jc...@ec...>]

Le 27. 11. 14 15:01, Paul Fertser a écrit :
> Hi,
>
> On Thu, Nov 27, 2014 at 02:33:09AM +0100, Jean-Christian de Rivaz wrote:
>> I initially tried with the FTDI Icebear probe using the
>> swd-resistor-hack.cfg (see my OP). It work fairly well but can fail when
>> programming the flash. I suspect that this can be caused by a SWD WAIT.
> Please see if http://openocd.zylin.com/#/c/2268/ helps.
>
>>> WAIT handling is not yet implemented at
>>> all, so for the target devices like nrf51 that really need it, we can
>>> only suggest using cmsis-dap or stlink for now.
>> I am afraid that I don't understand correctly this part. Should I use
>> cmsis-dap or stlinkfor the SAMD21 ?
> Likely not, I hope 2268 will solve the issue.


Correct, but using bad and unreliable workaround.

I have investigated modifications of my patch to resend the last 
operation when a WAIT response is received. Using an logic analyser that 
decode SWD protocol I have found that the SAMD21 do not reply to the 
resent operations and do not reply to the multiple W_ABORT after that. 
Adding delay up to 100ms after the WAIT response don't change the situation.

I don't understand why resending the last operation after a WAIT 
response don't work like mentioned into the "ARM Debug Interface v5® 
Architecture Specification" document. I am lost here.

Jean-Christian