ESP32 Forum

Is there any reason that pins GPIO33 and 34 are not populated on devkit?
I know they are used in chip with 8MB PSRAM, just like GPIO35-37. The thing is the later are populated and only those 2 are missing.

chegewara wrote: ↑

Sun Oct 24, 2021 10:44 am

Is there any reason that pins GPIO33 and 34 are not populated on devkit?
I know they are used in chip with 8MB PSRAM, just like GPIO35-37. The thing is the later are populated and only those 2 are missing.

right - they are used in chip with 8MB PSRAM, just like GPIO35-37.

rudi ;-) wrote:

chegewara wrote: ↑

Sun Oct 24, 2021 10:44 am

Is there any reason that pins GPIO33 and 34 are not populated on devkit?
I know they are used in chip with 8MB PSRAM, just like GPIO35-37. The thing is the later are populated and only those 2 are missing.

right - they are used in chip with 8MB PSRAM, just like GPIO35-37.

I know they are used on boards with 8MB, just two but:
- i have board with 2MB, so there is missing 2 pins that i could use
- on boards with 8MB psram we have 4 pins that cant be used

Then, where is the logic?

The logic likely is that we want to be able to use the devboards for all variants of the ESP32S3 and we want to lower the amount of people getting into trouble because they accidentally hook up a PSRAM/flash pin to an external peripheral.

ESP_Sprite wrote: ↑

Mon Oct 25, 2021 1:12 am

The logic likely is that we want to be able to use the devboards for all variants of the ESP32S3 and we want to lower the amount of people getting into trouble because they accidentally hook up a PSRAM/flash pin to an external peripheral.

I understand the idea, but:
- the same design is used for all 3 versions: no psram, 2MB psram, 8MB psram
- pins GPIO33-34 are used only in version with 8MB psram, those pins are not populated, to not cause problems,
- pins GPIO35-37 are also used only in version with 8MB psram, those are populated and can cause problems.

So, how pins gpio33-34 are problematic and 35-37 are not problematic to users?

I am not complaining or criticizing design, just i wanted to know if there is problem with those 2 pins.

Because we want to design a compatible package with ESP32-WROOM-32, we use same dimensions, same pin size, same pin pitch. But ESP32-S3 has more pins, we could only add two more pins on the bottom side of the module, then we discard two pins.

Thank you.