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I am new to ESP32, and I had do the same project with Arduino and it's working fine, now I am trying the same project to control 8 channel relays with an ESP32 Wroom 32, but I am not able to choose which pins used to connect to relay board and the ESP32.
Please help me to understand the raw pin number and board pin number connection ESP WROOM 32 Board.
The problem here is that you haven't identified the board. The ESP-WROOM-32 is just the module at the top of this board.
By doing a reverse image search I see that this board is one of those cheap Chinese breakout boards sold under a dozen different names with no documentation or diagrams. I'm sorry you've got sucked into this — the market is rife with this junk at the moment. You hear the the Espressif ESP32 is a reputable bit of gear (which it is), but you end up buying these high volume, zero effort, cheap cash grabs.
There is no way anyone can answer your question given the information you've provided. You've been sold a puzzle, not a product.
By digging a little further I see one of the potential origins of this board is the DOIT ESP32 DEVKIT V1. Going down that rabbit hole a little further I see they at least published some schematics. I found the link here, but that page itself is not useful.
Part of the very rough schematics is this section, which shows the pin mapping between the ESP32 and the pin headers.
For example, the pin marked D13 on your board corresponds to pin 3 of J1, which is connected to pin 16 of the ESP32, which is its GPIO13/AD2_4/T4/SD_D3 pin. You should be able to figure out the rest of the mappings from there.
Note that there is no guarantee that the board you have faithfully implements this schematic, but there's a high likelihood. Given this as a starting point you should at least be able to easily confirm the mapping with a multimeter in continuity mode.
