ESP32 Forum

Hi,
I'm just getting started with ESP32, and have designed a PCB for the ESP-WROOM-32 that I've just delivered for production.

While waiting for the PCB to be shipped I read in Kolbans book that:

Note that GPIO_NUM_34 – GPIO_NUM_39 are input mode only. You can not use these pins
for signal output. Also, pins 6, 7, 8, 9, 10 and 11 are used to interact with the SPI flash
chip ... you can not use those for other purposes. - page 183

So, going back to my schematics I see that I've connected some of the pins;

• pin 6 is going to output a PWM signal
• pin 7 has been set up to be an interrupt-input from an accelerometer.
• pin 8 to drive a LED

Does the quote above mean that these three connections I've made won't work?

Please clarify what you mean by 'pins of ESP-WROOM32':
- physical pads of the module, numbered from 1 to 38, or
- ESP32 GPIO numbers which are connected to these pads.

Kolban's book refers to GPIO numbers. Using GPIOs 6-8 will indeed be problematic because these pins are internally connected to SPI flash chip.

Hi,
I'm referring to physical pads on the ESP-WROOM-32.
Pad 6 (IO34), pad 7 (IO35) and pad 8 (IO32).

But you're saying that the unusable pins are IO6, IO7, IO8, IO9, IO10 and IO11? As far as I can tell none of those are broken out to physical pads, which would make my PCB design OK.

Scalpel78 wrote:Hi,
I'm referring to physical pads on the ESP-WROOM-32.
Pad 6 (IO34), pad 7 (IO35) and pad 8 (IO32).

But you're saying that the unusable pins are IO6, IO7, IO8, IO9, IO10 and IO11?

Yes, that's correct.

Scalpel78 wrote:As far as I can tell none of those are broken out to physical pads, which would make my PCB design OK.

Yes, it's OK. The only caveat is that IO34 is one of the input-only pins, so outputting a PWM signal on this pin will not work.