Clarification re. GPIO matrix and IO Mux

[permal]

Hi,

The document ESP32 Chip Pin List states the following:

The page "GPIO_Matrix" is for the GPIO-Matrix. The signals of the on-chip functional modules can be mapped onto any GPIO pins.
Some signals can be mapped onto a pin by both IO-MUX and GPIO-Matrix, as shown in the column tagged as "The same input signal from IO_MUX
Core" on the page "GPIO_Matrix".

Have I understood it correctly that any pin of any function can be remapped to any GPIO? For example, is it possible to remap VSPICS0 to GPIO16 and VSPICLK to GPIO17?

[WiFive]

Yes. Any function listed in gpio matrix signals list. Some signals only listed in MUX list restricted to those pins.

[ESP_igrr]

For example, JTAG, SD HOST, SDIO SLAVE, EMAC can not be remapped to other pins using the GPIO matrix (except for a few signals in SD HOST and EMAC). SPI, I2S and all the low speed peripherals can be remapped. As WiFive said, check the list of GPIO matrix signals.

[permal]

Ok, so that means that I can't have both JTAG and Ethernet running at the same time since they both use the MTMS-pin (17), right?

By pulling MTDO/GPIO15 low, you can disable the debug logging on U0TXD, but if doing that by grounding it, you also prevent MTDO to be used by anything else unless you have some control logic that only pulls it low during reset etc. If you don't ground it you potentially risk sending data to whatever is connected to the U0TXD pin during boot. Of course, with a proper line protocol this won't harm anything, but am I thinking about this correctly? Is some control logic actually needed?

[WiFive]

It depends on what you are using the pin for. Some case a pulldown resistor is fine, other case may need a switch.

[permal]

Ok, at least I'm thinking about it correctly.