ESP32-WROOM-32E dual chip pinouts

[Chillance]

Hi!

So, I'm using an ATSAMD51J20 to talk to this ESP32-WROOM-32E module and would like to get some advice on how exactly pins are mapped and how to best connect it up since I'm having issues talking to it and would like to confirm things before I do another set of hardware prototypes.

As far as I understand it, it has the ESP-AT firmware flashed from factory and to communicate using these AT commands, according to https://docs.espressif.com/projects/esp ... p32-series you would use:
GPIO16 (RX) (pin 27) is connected to PA04 on the SAMD5
GPIO17 (TX) (pin 28) is connected to PA05 on the SAMD5
GPIO15 (CTS) (pin 23) is connected to PA07 on the SAMD5
GPIO14 (RTS) (pin 13) is connected to PA06 on the SAMD5

CTS and RTS aren't really used, but they are there just in case.

EN (pin 3) is connected to PB15 on the SAMD5.

GPIO00 (pin 25) is connected through a 10k pullup to 3.3V. Button connects to GND.
GPIO02 isn't connected (floating?).
GPIO04 isn't connected (floating?).

TXD0 (pin 35) and RXD0 (pin 34) were wrongly connected to PB22 and PB23 which wouldn't work unfortunately since RXD0 should have been connected to a PAD0 pin on the SAMD5 (TX needs to be on a pin that is PAD0 apparently). But if communication is through the other set (UART1) then this shouldn't matter, right?

PB15 is set as output and high, so EN pin should have 3.3V. Rest should be fine I guess, and it should boot up into the AT commands firmware...

So, does anyone here see anything wrong/missing here? I'm testing with a simple firmware in the SAMD5 that is essentially sending "" (empty string) to just test the connection to the ESP32-WROOM-32 module, but that fails. I think I get a timeout.

Obviously there are many things that can be at fault here, but I figured I put this out there for feedback on this at least while I'm investigation further. One thing that makes this a bit confusing is that from what I've seen others do is to connect TXD0 (pin 35) and RXD0 (pin 34) to use this AT command firmware. So, if that is the case, what's with the UART1 usage? What am I missing here? If UART0 is suppose to be used that explains why it's not working for me but then I don't understand the documentation.

Thanks,
Chillance

[becorey]

since I'm having issues talking to it and would like to confirm things before I do another set of hardware prototypes.

Can you breadboard your design to confirm the connections before doing hardware prototypes? It can be wasteful to test out new connections with a pcb layout, as you're experiencing right now. Always test it first.

I'm testing with a simple firmware in the SAMD5 that is essentially sending "" (empty string) to just test the connection to the ESP32-WROOM-32 module, but that fails. I think I get a timeout.

Can you try sending anything other than an empty string? Maybe that looks like no data was sent so it keeps waiting. Send a simple int or string you can verify was received.

[ESP_Sprite]

So, does anyone here see anything wrong/missing here? I'm testing with a simple firmware in the SAMD5 that is essentially sending "" (empty string) to just test the connection to the ESP32-WROOM-32 module, but that fails. I think I get a timeout.

...What do you expect to go over the serial line when you send an empty string?