ESP32 serial2 does not send anything

Sandwich1699975 · January 22, 2023, 5:11am

I have an ESP32 DOIT DEV V1 3.3v:

I can confirm that the SMS hat can send and receive AT commands through serial correctly. As discussed here.

I would like to use both hardware serial ports on the ESP32 to debug and talk to the hat at the same time. Serial1 for USB debug, and Serial2 for the SMS hat.

This is the test code I'm using:

#include <HardwareSerial.h>

void setup() {
Serial.begin(115200);
Serial2.begin(115200, SERIAL_8N1, 16, 17);
}

void loop() {
  if (Serial2.available() > 0) {
    Serial.write(Serial2.read());
  }
  if (Serial.available() > 0) {
    Serial2.write(Serial.read());
  }
}

^{*Unplugged for photo. TX -> TX and RX -> RX is how it's meant to be. Please see here.}

esptool.py:

Detecting chip type... ESP32
Chip is ESP32-D0WDQ6 (revision v1.0)
Features: WiFi, BT, Dual Core, 240MHz, VRef calibration in efuse, Coding Scheme None
WARNING: Detected crystal freq 41.01MHz is quite different to normalized freq 40MHz. Unsupported crystal in use?
Crystal is 40MHz
MAC: 30:ae:a4:f4:d0:b8
Uploading stub...
Running stub...
Stub running...
Manufacturer: 20
Device: 4016
Detected flash size: 4MB
Hard resetting via RTS pin...

I can receive input through serial, But I can't send anything to the HAT.

Why isn't serial 2 TX working?

red_car · January 22, 2023, 5:49am

Can you try connecting the Tx pin of the ESP32, to the Rx pin of your USB/TTL adapter (and GND to GND), and run the following.

#include <HardwareSerial.h>

void setup()
{
  Serial2.begin(115200, SERIAL_8N1, 16, 17);
}


void loop()
{
  Serial2.println(millis());
  delay(2000);
}

Would be good to understand which side of the ESP32-SIM67600 communication is not working.

red_car · January 22, 2023, 7:38am

OK... I did a bit of playing with an ESP32, and my SIM7600 (the one that works ok).

I used your code and got nothing returned. After a bit of digging I believe the issue is with the way you are declaring the 2nd serial port. Try this version...

#include <HardwareSerial.h>

HardwareSerial SerialPort2 (2);   // This is the key line missing.

void setup()
{
  Serial.begin(115200);
  SerialPort2.begin(115200, SERIAL_8N1, 16, 17);
}

void loop()
{
  while (Serial.available() > 0)
    SerialPort2.write(Serial.read());
    
  while (SerialPort2.available() > 0)
    Serial.write(SerialPort2.read());
}

Interestingly, if I called it "Serial2" instead of "SerialPort2" it fails to compile.

J-M-L · January 22, 2023, 8:36am

It’s because it’s already there line 108

github.com

espressif/arduino-esp32/blob/2333df5ac650fd9ebc0a1a0d7df93851c86a95e1/cores/esp32/HardwareSerial.cpp#L108


      
          #if !defined(NO_GLOBAL_INSTANCES) && !defined(NO_GLOBAL_SERIAL)
          #if ARDUINO_USB_CDC_ON_BOOT //Serial used for USB CDC
          HardwareSerial Serial0(0);
          #else
          HardwareSerial Serial(0);
          #endif
          #if SOC_UART_NUM > 1
          HardwareSerial Serial1(1);
          #endif
          #if SOC_UART_NUM > 2
          HardwareSerial Serial2(2);
          #endif
          
          
void serialEventRun(void)
          {
          #if ARDUINO_USB_CDC_ON_BOOT //Serial used for USB CDC
              if(Serial0.available()) serialEvent();
          #else
              if(Serial.available()) serialEvent();
          #endif
          #if SOC_UART_NUM > 1

red_car · January 22, 2023, 8:42am

Noted. Where does this get set?

J-M-L · January 22, 2023, 9:03am

In here for example

github.com

espressif/arduino-esp32/blob/8ee5f0a11e5423a018e0f89146e05074466274db/tools/sdk/esp32s3/include/soc/esp32s3/include/soc/uart_caps.h#L24


      
          
          
#pragma once
          
          
#ifdef __cplusplus
          extern "C" {
          #endif
          
          
#define SOC_UART_FIFO_LEN          (128)      /*!< The UART hardware FIFO length */
          #define SOC_UART_BITRATE_MAX       (5000000)  /*!< Max bit rate supported by UART */
          
          
#define SOC_UART_NUM           (3)
          
          
// UART has an extra TX_WAIT_SEND state when the FIFO is not empty and XOFF is enabled
          #define SOC_UART_SUPPORT_FSM_TX_WAIT_SEND   (1)
          
          
#ifdef __cplusplus
          }
          #endif

I suppose it depends on your board that one is for esp32s3

Here it is for the standard ESP32

github.com

espressif/arduino-esp32/blob/bcc1d758fc343887de03affeedfbb33522ff2523/tools/sdk/esp32/include/soc/esp32/include/soc/soc_caps.h#L265


      
          #  define SOC_TWAI_BRP_MAX              256
          #  define SOC_TWAI_BRP_DIV_SUPPORTED    1
          #  define SOC_TWAI_BRP_DIV_THRESH       128
          #else
          #  define SOC_TWAI_BRP_MAX              128
          #endif
          #define SOC_TWAI_SUPPORT_MULTI_ADDRESS_LAYOUT   1
          
          
/*-------------------------- UART CAPS ---------------------------------------*/
          // ESP32 have 3 UART.
          #define SOC_UART_NUM                (3)
          #define SOC_UART_SUPPORT_REF_TICK   (1)         /*!< Support REF_TICK as the clock source */
          #define SOC_UART_FIFO_LEN           (128)       /*!< The UART hardware FIFO length */
          #define SOC_UART_BITRATE_MAX        (5000000)   /*!< Max bit rate supported by UART */
          
          

          
/*-------------------------- SPIRAM CAPS -------------------------------------*/
          #define SOC_SPIRAM_SUPPORTED    1
          
          
/*--------------------------- SHA CAPS ---------------------------------------*/
          /* ESP32 style SHA engine, where multiple states can be stored in parallel */

red_car · January 22, 2023, 9:27am

I'm using an ESP32-WROOM-32U... closest board I could find is ESP32-WROOM-DA Module.

However, although Serial2 seems to be defined (and when I print SOC_UART_NUM = 3), the serial port does not work. It only works if I define with a different name ?

J-M-L · January 22, 2023, 11:16am

What pins did you use ?

sumguy · January 22, 2023, 3:43pm

In your picture you have TX to TX and RX to RX it should be TX to RX and RX to TX

red_car · January 22, 2023, 5:57pm

16 (Rx), 17 (Tx).

red_car · January 22, 2023, 5:59pm

No it shouldn't. The pin labels on the HAT refer to the Raspberry Pi, not the SIM7600.

sumguy · January 22, 2023, 7:36pm

OK my bad, thanks for the correction

J-M-L · January 22, 2023, 11:22pm

Sounds right
Did you try with any example?

sumguy · January 23, 2023, 4:32am

So the P-TX to RX-3.3v and P-RX to TX-3.3v works with Arduino (5v) but not ESP32 (3.3v) so the UART header is probably right what about the UART voltage selection is that set to 3.3v (default). Can you adjust the UART header and get a response sending AT commands over USB just to take any external module out of the equation.

Edit : the tx rx connections I refer to are the ones at the uart header.

Sandwich1699975 · January 23, 2023, 6:05am

I can't communicate over a 5 volt USB TTL adaptor (RX TX header) to the hat, But I can send AT commands through the Arduino UNO (RX TX header) to the hat, and the Shield's built-in USB port.

Sandwich1699975 · January 23, 2023, 6:11am

Works as expected here:

Output from USB:

Sandwich1699975 · January 23, 2023, 6:24am

No Luck from this one. I can't send anything to the HAT, and the USB UART adaptor doesn't work with this either. for some reason

Which doesn't make much sense if I could receive from the last script. But when I boot my 3rd party serial monitor for the USB the TX light gets stuck on. If i disconnect and plug back it it turns off

red_car · January 23, 2023, 7:01am

Ok so can you just confirm what works and what doesn't...

Uno hardware with blank sketch (effectively sending to/from commands from the IDE serial monitor)?
Uno Software serial? Using pass-through sketch?
ESP32 using pass-though sketch ? (using port 0 monitor, and port 2 for SIM7600). You get boot messages but can't send commands?
USB/TTL adapter and your 3rd party monitor doesn't work?

PS. My ESP32 is now working fine using Serial2... don't need to rename as per post #3... but at the time it definitely wasn't so not sure what changed... I should have been more methodical when playing around.

Sandwich1699975 · January 24, 2023, 1:00am

I went back and re-did all of these tests to be sure

115200 baud
UNO can send and relieve data from SMS hat.
UNO can't receive data from TX2 on ESP32, but can send data to RX2
- This is wired TX UNO -> TX2 ESP32 & RX UNO RX2 ESP32

9600 baud for software serial
UNO can talk to the SMS hat perfectly fine
UNO can send to the ESP32 Serial2 fine, but cannot receive from it

115200 baud
Correct, I get the boot and can't send messages
The use of HardwareSerial SerialPort2 (2); didn't make a difference. I had trouble getting it to work at all a min ago, so I deleted it and used the code below. Which gets the boot message at least.

#include <HardwareSerial.h>


void setup()
{
  Serial.begin(115200);
  Serial2.begin(115200, SERIAL_8N1, 16, 17);
}

void loop()
{
  while (Serial.available() > 0)
    Serial2.write(Serial.read());
    
  while (Serial2.available() > 0)
    Serial.write(Serial2.read());
}

Correct. I can't talk to the hat at all. As soon as I connect on the serial monitor, the TX light on the USB turns solid red even through I'm not sending anything. When resetting the SMS hat, the RX light flashes once for some reason.

system · July 23, 2023, 1:01am

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ESP32 serial2 does not send anything

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