esp 32 - problems redefining tx and rx pins on Serial 0 on version 2.0.13 and 2.0.14

[xalier1]

Board

LOLIN s2 mini

Device Description

no other hardware other the LOLIN s2 mini board required

Hardware Configuration

A jumper between the tx and rx pins is needed to show functionality with the sketch provided.

Version

v2.0.14

IDE Name

Arduino IDE

Operating System

Windows 10

Flash frequency

Not sure - not changed from default.

PSRAM enabled

no

Upload speed

921600

Description

Upgrading from version 2.0.12 to 2.0.14 broke the sketch below until the statement " Serial0.end(true);" was added before the Serial0.begin() statement. The Serial0.end() statement is not required in this sketch if this sketch is run on 2.0.12 or earlier.

Sketch

int count = 0;

void setup() {
         unsigned long start = micros();
         Serial.begin(9600);     // opens serial port, sets data rate to 9600 bps
         while (!Serial  && ( (micros() - start) < 1*1000*1000l)) {
            delay(1);
         }
         if(!Serial) {
          Serial.println("timed out waiting for Serial");
         }
         Serial.println("Starting test");
         //Serial1.begin(9600);
         Serial0.end(true);  // not required by 2.0.12 but required by 2.0.13 and 14
         Serial0.begin(9600, SERIAL_8N1, 37, 39); // rx=37, tx=39 for wemos esp32s2
         // need to jumper pins 37 to 39 to get a uart loopback
         Serial0.println("Counter: "+String(count++)); 
}

void loop() {
  static unsigned long lastTM=millis();  // close enough to send in setup()

  static String x="";
  while (Serial0.available() > 0) {
    // read the incoming byte:
    char incomingByte = Serial0.read();
    x += incomingByte;
  }

  if( millis() - lastTM > 1*1000) {
    lastTM = millis();
    if( x != "" ) {
      Serial.print("Received: "+x);
      x ="";
    }
    else {
      Serial.println("Timed out on receive");
    }    
    Serial0.println("Counter: "+String(count++));
  }
}

Debug Message

No debug messages go to USB console when core debug level is set to verbose on this LOLIN s2 mini board.

Other Steps to Reproduce

Important to jumper pins 37 to 39 to connect RX to TX for the serial0 uart to be able to receive what is sent to allow the provided sketch to run without receive timeouts messages.

In looking at the differences between HardwareSerial.cpp for 2.0.12 and 2.0.14, there appear to be changes that assume that serial0 is special and associated with the console. The LOLIN-MINI-S2 uses the "USB CDC on boot:Enabled" setting on the Arduino IDE since there is no independent chip on the board to translate from an esp uart to the usb for the console. Changes to the 2.0.14 hardwareserial.cpp code provided a clue to terminate Serial0 before using the serial0.begin statement to define the uart rx and tx pins. The changes in HardwareSerial.cpp from 2.0.12 to 2.0.14 seem to be tuned to support a console for a board that has a console associated with serial0. I can change my code permanently to call serial0.end() before serial0.begin is called if that is recommended as a work around solution going forward. If no code changes are planned, please suggest a way to allow use of serial0 with user configurable rx and tx pins on boards like the LOLIN s2 mini that is unlikely to break in future releases.

I have checked existing issues, online documentation and the Troubleshooting Guide

• I confirm I have checked existing issues, online documentation and Troubleshooting guide.

[VojtechBartoska]

@SuGlider Please help with the triage.

[SuGlider]

Issue with 2.0.14 confirmed. I'll test it with the code in the release/v2.x and, if necessary, fix it there for the 2.0.15.
This issue doesn't happen with 3.0.0-Alpha-3, which uses a refactored UART code.

@xalier1 - please stick to the 2.0.13 for now. 2.0.15 shall fix it and some other HardwareSerial issues.

[xalier1]

@SuGlider - thanks for investigating this. Just to make sure that you are seeing the same problem that I am, the problem also exists on 2.0.13. I had to revert to 2.0.12 for the problem to not occur.

[SuGlider]

@xalier1 - yes. I'll dig into it and fix it for 2.0.15.

[SuGlider]

Fix by #9373
To be released within 2.0.15