JTAG, VSIP and EMAC pins

Posts: 7
Joined: Tue May 29, 2018 2:11 pm

JTAG, VSIP and EMAC pins

Postby habibh » Tue Jun 05, 2018 8:14 am


I am going to use ESP32-PICO-D4 in my project with external flash and sRAM. I want to use VSPI in my project for communicating with external flash and sRAM. The SPI pins are already used in ESP32-PICO-D4 for connecting embedded flash and these pins cannot be used. So my question is if i am using VSPI pins and JTAG pins than i will not be able to use Ethernet funcction of ESP32-PICO-D4 in my project ?
In the attachment I have highlighted the pins that are shairing the same functionality..

ESP32 Pins.PNG
ESP32 Pins.PNG (270.84 KiB) Viewed 763 times

Posts: 37
Joined: Fri Aug 24, 2018 1:14 pm

Re: JTAG, VSIP and EMAC pins

Postby phatpaul » Fri Oct 19, 2018 6:27 pm

Seems I'm unable to use JTAG and Ethernet at the same time.
I'm not sure what's going on exactly.

I don't see how the pins are shared because I'm not using GPIO13/MTCK for anything other than JTAG (it is apparently not required for Ethernet RMII, although some documentation lists it as EMAC_RX_ER).

When I start-up with JTAG connected, the emacT task fails to init the PHY chip (LAN8720).

But if I temporarily disconnect JTAG, then emac starts up fine and then I can reconnect JTAG and both works fine.
Currently it's just an annoyance for me, not a show-stopper. But I'd like to know how to fix it.

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