ESP32 Forum

I have GPIO12 pulled high through a 10k resistor, and I believe I have followed the various other documented pin rules when enabling usage of the embedded flash on this chip.

However, I am a little unclear if I need any special strapping for the MTDO and GPIO5 pins, to configure rising/falling edge timing, when using this embedded flash. I have not seen any comments on this in any forums, so I presume I can just leave them as default/floating?

I need those pins for other components, so it would be nice to know they don't need any special configuration.

Thanks.

Hi Brento,

I think the confusion here is over the "Timing of SDIO Slave" table in section "2.4 Strapping Pins" of the ESP32 datasheet.

This is only something you need to be concerned about if using the SDIO Slave peripheral. Booting ESP-IDF from the embedded flash chip doesn't involve the SDIO Slave peripheral at all (it's not related to the SPI Flash controller), so this table probably doesn't apply.

Separately to that, MTDO can be pulled high (default) or low on reset, but if pulled low then you won't receive any UART output during early boot. This output can be pretty useful when doing initial board bringup.

Ok, I will leave GPIO and MTDO floating, since it does not apply here.

I will rely on MTDO's default pull-up when left floating, since it sounds like that would be valuable for debugging.