ESP8266 Community Forum

- Wed Sep 24, 2014 6:58 pm #895

Kind of a newbie on the start from nothing trail. I have an ESP-01 and am wondering where I would connect the JTAG. I have not found that documentation anywhere. This forum has been a tremendous help as far as getting an IDE up and running and the xtensa OCD, but if I had the correct JTAG, how would I connect it without a microscope. I may be missing something.

viewtopic.php?f=9&t=142&p=758&hilit=jtag#p758

- Wed Sep 24, 2014 7:15 pm #896

i have an ESP-01 and am wondering where I would connect the JTAG.

unfortunately the MTDO pin is connected to GND on ESP-01 module, and unfortunetly the gnd trace is under the chip. So no, you would have to desolder first the ESP8266, but the gnd trace and solder it back (or even better solder on differen board and not that crap ESP-01 module). You can of course use ESP-03 or ESP-04, on them there is no problem with MTDO.

I don't want to be human! I want to see gamma rays, I want to hear X-rays, and I want to smell dark matter ...
I want to reach out with something other than these prehensile paws and feel the solar wind of a supernova flowing over me.

- Fri Oct 10, 2014 6:55 am #1508

The Xtensa core used in the ESP8266 has support in OpenOCD. OpenOCD works with common ARM JTAG units. JTAG is the same everywhere so these 'ARM' JTAGs should work on the ESP8266 too.

JTAG has several advantages. It can use several different schemes to program the flash chip. JTAG can also provide source level debugging and single step. OpenOCD is already integrated with gdb.

As soon as someone get some hardware it would interesting to see what you can do with OpenOCD.

Could you point me to the version of OpenOCD you found which supports Xtensa cores? I only find some old discussions about it on http://lists.linux-xtensa.org/pipermail/openocd-xtensa/
The hardware is here on my table , just need OpenOCD now

- Fri Oct 10, 2014 9:22 am #1511 none of the version between 0.1.0 and 0.8.0, they simply don't know any tensilica nor xtensa target.

It could be easier to use the "Xtensa OCD Daemon 8.0.1" (the one provided with the VM) and that provided SDK to create own control driver, as said here :

viewtopic.php?f=6&t=12&p=1400&hilit=jtag#p1400

I don't want to be human! I want to see gamma rays, I want to hear X-rays, and I want to smell dark matter ...
I want to reach out with something other than these prehensile paws and feel the solar wind of a supernova flowing over me.