[LEDE-DEV] Archer c7 corrupted firmware bootloop - tftp aborting - serial not working

[Russell Senior]

>>>>> "Alberto" == Alberto Bursi <alberto.bursi at outlook.it> writes:

Alberto> On 06/04/2017 02:54 PM, QWeRKUS qwErkus wrote:
>> Thank you for your reply. JTAG seems even trickier than serial. So
>> far all my attempts to scan for a valid JTAG chain end up with:
>> 
>> Error: JTAG scan chain interrogation failed: all zeroes
>> 
>> There a just too many variables to check for a newbie like myself, so
>> I guess I'll go with the spi programmer. Turns out this is another
>> thing the pi can do (via flashrom) so no need for new hardware. Are
>> you sure you need to desolder the chip though ? Shouldn't this be
>> working with a 8 pin SOIC clamp and and external 3.3V power source (I
>> have an old ATX PSU doing the job) ?
>> 
>> 
Alberto> It should, but in some cases it does not (depends from how the
Alberto> board was designed) and in those situations you need to
Alberto> desolder the chip. I got most of these "cases where it does not
Alberto> work" in PC and laptop boards though.

If the CPU is trying to access the SPI bus at the same time, it can be
problematic.  On a TP Link WDR3600 board, I had to figure out how to
hold the CPU in reset.  You might be able to do that from the JTAG nSRST
pin.  Make sure it's connected.  On the WDR3600 board, there was a shunt
resistor missing.

  http://www.jtagtest.com/pinouts/ejtag

Tie nSRST to ground with a jumper wire or similar, attach your SOIC
clip, and run flashrom.


-- 
Russell Senior, President
russell at personaltelco.net