Cannot make ESP32 communicate with ThinkerAI A9G board via UART

Question

I want to use ThinkerAI A9G module via it AT commands, but i cannot make my ESP32 communicate with it. I have connected them but all i get is some strange random symbols. As i understand i could be caused by not matching baud rates, but i have tried all most popular baud rates and tried sending "AT" command to A9G so that it changes its baud rate to match mine, but i always get the same result. Also tried SoftwareSerial, but with it i was not getting anything in my terminal at all.

So heres my setup:

So my ESP32 is connected to A9G like this (left side is esp32):

1. VBUS <-> VUSB
2. GND <-> GND
3. PIN2 <-> TX
4. PIN4 <-> RX

And heres my Arduino sketch:

#include <Arduino.h>

void setup() {
  Serial.begin(115200);

  Serial1.begin(115200, 2, 4); //Here, as i understand i set pin2 to RX and pin4 to TX
}
void loop() {
  while (Serial.available() > 0) {
    Serial1.write(Serial.read());
  }
  while (Serial1.available() > 0) {
    Serial.write(Serial1.read());
  }
}

And when i power everything up, open serial monitor and click "Reset on A9G" i get this:

And when i send any AT commands it doesn't respond. So i suppose i got something wrong and it is not working properly. So i would like to know how to fix this issue and to communicate with A9G.

Upd: was able to get an output to terminal using SoftwareSerial, by setting inverse to true (TX pin on A9G in high when nothing is transmitted, checked with oscilloscope, so not sure if that was the right decision just experimenting to try to make it work), but still i get random junk in the terminal. Sketch:

#include <SoftwareSerial.h> 
SoftwareSerial softSerial(2, 4, 1);

void setup() {
  Serial.begin(115200);

  softSerial.begin(115200);
}
void loop() {  
    while (Serial.available() > 0) {
      softSerial.write(Serial.read());
    }
    while (softSerial.available() > 0) {
      Serial.write(softSerial.read());
    }
}

Result:

Also heres the images of the components that i am using (if its any help):

1. ESP32-S2-MINI

2. ThinkerAI A9G development board

Answer 1

Looks like it was a hardware problem, more precisely with a wires, that i have used to connect A9G with Esp32 which made connection unreliable and because of this i couldn't get an output. After soldering everything, i was able to get an output with this sketch:

#include <SoftwareSerial.h> 
SoftwareSerial softSerial(2, 4);

void setup() {
  Serial.begin(115200);

  softSerial.begin(115200);
}
void loop() {  
    while (Serial.available() > 0) {
      softSerial.write(Serial.read());
    }
    while (softSerial.available() > 0) {
      Serial.write(softSerial.read());
    }
}

And this is what i got after clicking Reset button on A9G:

Init...
00:25:36.737 -> 
00:25:38.296 -> NO SIM CARD
00:25:38.296 -> +CIEV: "Charging)⸮*
00:25:38.296 -> 
00:25:43.674 -> 
00:25:43.674 -> +CREG: 3
00:25:43.674 -> 
00:27:01.000 -> 
00:27:01.000 -> +CREG: 3
00:27:01.000 -> 

As you can see some characters are still corrupted (+CIEV: "Charging)⸮* should be +CIEV: "Charging",90%), but now it is at least usable. Thank you.

Heres the photo of bad connectors: