JTAG Daisy-Chaining
Posted: Thu Aug 24, 2017 2:59 am
by rezarethink
I'm planning on using the ESP32 along with an STM32. Is it possible to do JTAG daisy-chaining? And would both ICs need to be powered up for JTAG to work for either IC?
Thnx,
Reza
Re: JTAG Daisy-Chaining
Posted: Thu Aug 24, 2017 9:31 am
by ESP_Sprite
In theory, it should be possible to daisy-chain JTAG; the protocol is built for this. In designing the OpenOCD drivers, we've tried to take this scenario into account; however due to it not being a standard usage scenario, we can't guarantee we haven't missed something here or there. (If we did, feel free to report a bug and we'll fix it.) You do need to power both devices when you daisy-chain JTAG; the nature of the protocol makes it impossible for a powered-off device to pass along data in a compatible fashion.