Help with Hardware Serial

jackson_crawford · May 3, 2024, 3:17am

I am attempting to establish a Uart connection between an ESP32C3 XIAO seeeduino and a WT901B Wit-Motion accel, gyro, etc, sensor. I ended up getting a handshake with the two being wired but when I tried implementing them with a custom PCB it doesn't work. I found the issue with the PCB, the RX and TX were not connected properly as the photo I had used for reference was mirrored and I hadn't noticed, anyways I removed the tracers and just wired them but it still isn't working. I tried different serial ports on the ESP but it just wont connect. I really don't know what the issue could be I have tried a lot and I'm not sure what I'm missing. I think it's possible its my code but I didn't change it from what it was in working condition. My code consists of parts of the Wit-Motion supplied code and a timer among a few other things. I was also running into issues with the serial monitor, after about 5-10 seconds it stops displaying anything. I ended up using puTTy for reading it but I don't know why Serial monitor isn't working.

-Upload Settings-
USB CDC on boot -enabled
CPU frequency -160MHz
Core Debug -none
Erase All Flash... -enabled
Flash Frequency -80MHz
Flash Mode -QIO (I tried DIO too but didn't make a difference)
Flash Size -4MB
Upload Speed -512000 (I tried lowering but it just changes it back)
Programmer -Epstool

Code:

#include <REG.h>
#include <wit_c_sdk.h>
#include <HardwareSerial.h>
#include <chrono>
#include <Arduino.h>

bool UP = false;
bool DOWN = false;
bool NEUTRAL = false;

bool neutralOccurred = false;

#define ACC_UPDATE		0x01
#define GYRO_UPDATE		0x02
#define ANGLE_UPDATE	0x04
#define MAG_UPDATE		0x08
#define READ_UPDATE		0x80
static volatile char s_cDataUpdate = 0, s_cCmd = 0xff; 

HardwareSerial MySerial0(0);

static void CmdProcess(void);
static void AutoScanSensor(void);
static void SensorUartSend(uint8_t *p_data, uint32_t uiSize);
static void SensorDataUpdata(uint32_t uiReg, uint32_t uiRegNum);
static void Delayms(uint16_t ucMs);
const uint32_t c_uiBaud[8] = {115200};


class Timer {
public:
    Timer() : m_running(false), m_elapsedTime(0) {}

    void start() {
        if (!m_running) {
            m_startTime = millis();
            m_running = true;
        }
    }

    void stop() {
        if (m_running) {
            m_elapsedTime += millis() - m_startTime;
            m_running = false;
        }
    }

    void reset() {
        m_elapsedTime = 0;
        m_running = false;
    }

    unsigned long getElapsedTime() const {
        if (m_running) {
            return m_elapsedTime + (millis() - m_startTime);
        } else {
            return m_elapsedTime;
        }
    }

private:
    bool m_running;
    unsigned long m_startTime;
    unsigned long m_elapsedTime; // in milliseconds
};

Timer timer;

//********************

void setup() {
  Serial.begin(9600);
  MySerial0.begin(115200, 20, 21);
	WitInit(WIT_PROTOCOL_NORMAL, 0x50);
	WitSerialWriteRegister(SensorUartSend);
	WitRegisterCallBack(SensorDataUpdata);
  WitDelayMsRegister(Delayms);
	Serial.print("\r\n********************** wit-motion normal example  ************************\r\n");
	AutoScanSensor();

}
int i;
float fAcc[3], fGyro[3], fAngle[3];
void loop() {
    
  while (MySerial0.available())
    {
      WitSerialDataIn(MySerial0.read());
    while (Serial.available())
    {
      CopeCmdData(Serial.read());
    }
    CmdProcess();
    if(s_cDataUpdate)
    {
      for(i = 0; i < 3; i++)
      {
        fAcc[i] = sReg[AX+i] / 32768.0f * 16.0f;
        fGyro[i] = sReg[GX+i] / 32768.0f * 2000.0f;
        fAngle[i] = sReg[Roll+i] / 32768.0f * 180.0f;
      }
      if(s_cDataUpdate & ACC_UPDATE)
      {
        Serial.print("acc:");
        Serial.print(fAcc[0], 3);
        Serial.print(" ");
        Serial.print(fAcc[1], 3);
        Serial.print(" ");
        Serial.print(fAcc[2], 3);
        Serial.print("\r\n");
        s_cDataUpdate &= ~ACC_UPDATE;
      }
      s_cDataUpdate = 0;
    }


    if (sqrt((fAcc[0]*fAcc[0])+(fAcc[1]*fAcc[1])+(fAcc[2]*fAcc[2])) > 1.05)
      {
        DOWN = true;
        UP = false;
        NEUTRAL = false;
        Serial.print("Down-");
      }
      if (sqrt((fAcc[0]*fAcc[0])+(fAcc[1]*fAcc[1])+(fAcc[2]*fAcc[2])) < .95)
      {
        UP = true;
        DOWN = false;
        NEUTRAL = false;
        Serial.print("Up+");
      }
      if (  (sqrt((fAcc[0]*fAcc[0])+(fAcc[1]*fAcc[1])+(fAcc[2]*fAcc[2])) < 1.05)  &&  (sqrt((fAcc[0]*fAcc[0])+(fAcc[1]*fAcc[1])+(fAcc[2]*fAcc[2])) > .95)  )
      {
        NEUTRAL = true;
        UP = false;
        DOWN = false;
        Serial.print("Neutral=");
      }
handleEvents(UP, NEUTRAL);
handleEvents2(DOWN, NEUTRAL);
Show();

    }
}


//*******************************

void handleEvents(bool UP, bool NEUTRAL) {
    static bool upDetected = false; // Flag to track if UP has been detected

    if (UP && !upDetected) {
        upDetected = true; // Set UP detected
    } else if (upDetected && NEUTRAL) {
        // If UP has been detected and NEUTRAL occurs, perform the action
        timer.stop();
        upDetected = false; // Reset UP detection
    } else if (!UP && NEUTRAL) {
        // If NEUTRAL occurs without UP, reset UP detection
        upDetected = false;
    }
}

//*******************************

void handleEvents2(bool DOWN, bool NEUTRAL) {
    static bool downDetected = false; // Flag to track if DOWN has been detected

    if (DOWN && !downDetected) {
        if (neutralOccurred) {
            // If DOWN event occurs after NEUTRAL, start the timer
            timer.reset();
        }
        downDetected = true; // Set DOWN detected
    } else if (downDetected && NEUTRAL) {
        // If DOWN has been detected and NEUTRAL occurs, perform the action
        timer.start();
        downDetected = false; // Reset DOWN detection
    }

    // Update the state of NEUTRAL event
    neutralOccurred = NEUTRAL;


}

void Show()
{
  Serial.print(timer.getElapsedTime());
  Serial.print(" , milliseconds  :   ");
  delay(50);
}

//******************************

void CopeCmdData(unsigned char ucData)
{
	static unsigned char s_ucData[50], s_ucRxCnt = 0;
	
	s_ucData[s_ucRxCnt++] = ucData;
	if(s_ucRxCnt<3)return;										//Less than three data returned
	if(s_ucRxCnt >= 50) s_ucRxCnt = 0;
	if(s_ucRxCnt >= 3)
	{
		if((s_ucData[1] == '\r') && (s_ucData[2] == '\n'))
		{
			s_cCmd = s_ucData[0];
			memset(s_ucData,0,50);
			s_ucRxCnt = 0;
		}
		else 
		{
			s_ucData[0] = s_ucData[1];
			s_ucData[1] = s_ucData[2];
			s_ucRxCnt = 2;
			
		}
	}
}

static void CmdProcess(void)
{
	switch(s_cCmd)
	{
		case 'a':	if(WitStartAccCali() != WIT_HAL_OK) Serial.print("\r\nSet AccCali Error\r\n");
			break;
		case 'm':	if(WitStartMagCali() != WIT_HAL_OK) Serial.print("\r\nSet MagCali Error\r\n");
			break;
		case 'e':	if(WitStopMagCali() != WIT_HAL_OK) Serial.print("\r\nSet MagCali Error\r\n");
			break;
		case 'u':	if(WitSetBandwidth(BANDWIDTH_5HZ) != WIT_HAL_OK) Serial.print("\r\nSet Bandwidth Error\r\n");
			break;
		case 'U':	if(WitSetBandwidth(BANDWIDTH_256HZ) != WIT_HAL_OK) Serial.print("\r\nSet Bandwidth Error\r\n");
			break;
		case 'B':	if(WitSetUartBaud(WIT_BAUD_115200) != WIT_HAL_OK) Serial.print("\r\nSet Baud Error\r\n");
              else 
              {
                MySerial0.begin(c_uiBaud[WIT_BAUD_115200]);
                Serial.print(" 115200 Baud rate modified successfully\r\n");
              }
			break;
		case 'b':	if(WitSetUartBaud(WIT_BAUD_9600) != WIT_HAL_OK) Serial.print("\r\nSet Baud Error\r\n");
              else 
              {
                MySerial0.begin(c_uiBaud[WIT_BAUD_9600]); 
                Serial.print(" 9600 Baud rate modified successfully\r\n");
              }
			break;
		case 'r': if(WitSetOutputRate(RRATE_1HZ) != WIT_HAL_OK)  Serial.print("\r\nSet Baud Error\r\n");
			        else Serial.print("\r\nSet Baud Success\r\n");
			break;
		case 'R':	if(WitSetOutputRate(RRATE_10HZ) != WIT_HAL_OK) Serial.print("\r\nSet Baud Error\r\n");
              else Serial.print("\r\nSet Baud Success\r\n");
			break;
    case 'C': if(WitSetContent(RSW_ACC|RSW_GYRO|RSW_ANGLE|RSW_MAG) != WIT_HAL_OK) Serial.print("\r\nSet RSW Error\r\n");
      break;
    case 'c': if(WitSetContent(RSW_ACC) != WIT_HAL_OK) Serial.print("\r\nSet RSW Error\r\n");
      break;
		default :break;
	}
	s_cCmd = 0xff;
}
static void SensorUartSend(uint8_t *p_data, uint32_t uiSize)
{
  MySerial0.write(p_data, uiSize);
  MySerial0.flush();
}
static void Delayms(uint16_t ucMs)
{
  delay(ucMs);
}
static void SensorDataUpdata(uint32_t uiReg, uint32_t uiRegNum)
{
	int i;
    for(i = 0; i < uiRegNum; i++)
    {
        switch(uiReg)
        {
            case AZ:
				s_cDataUpdate |= ACC_UPDATE;
            break;
            case GZ:
				s_cDataUpdate |= GYRO_UPDATE;
            break;
            case HZ:
				s_cDataUpdate |= MAG_UPDATE;
            break;
            case Yaw:
				s_cDataUpdate |= ANGLE_UPDATE;
            break;
            default:
				s_cDataUpdate |= READ_UPDATE;
			break;
        }
		uiReg++;
    }
}

static void AutoScanSensor(void)
{
	int i, iRetry;
	
	for(i = 0; i < sizeof(c_uiBaud)/sizeof(c_uiBaud[0]); i++)
	{
		MySerial0.begin(c_uiBaud[i]);
    MySerial0.flush();
		iRetry = 2;
		s_cDataUpdate = 0;
		do
		{
			WitReadReg(AX, 3);
			delay(200);
      while (MySerial0.available())
      {
        WitSerialDataIn(MySerial0.read());
      }
			if(s_cDataUpdate != 0)
			{
				Serial.print(c_uiBaud[i]);
				Serial.print(" baud find sensor\r\n\r\n");
				return ;
			}
			iRetry--;
		}while(iRetry);		
	}
	Serial.print("can not find sensor\r\n");
	Serial.print("please check your connection\r\n");
}

This is the PCB (the WT901B is getting power):

horace · May 3, 2024, 5:34am

GPIO20 U0RXD and GPIO21 U0TXD are used for Serial programming/debugging
and you have specified pins 20 and 21 for

  MySerial0.begin(115200, 20, 21);

hence Serial does not work

the following code for a ESP32-C3-MINI-1 uses pins 2 and 3 for Serial1

// ESP32-C3-MINI-1 Serial1 test - for loopback test connect pins 2 and 3

// note GPIO20 U0RXD and GPIO21 U0TXD are used for Serial programming/debugging

#define RXD1 3
#define TXD1 2

void setup() {
  // initialize both serial ports:
  Serial.begin(115200);
  Serial1.begin(115200, SERIAL_8N1, RXD1, TXD1);
  Serial.println();
  Serial.println("\n\nESP32-C3 serial1  test Rx pin 3 Tx pin 2");
  Serial.write("   for loopback test connect pin 3 to pin 2\n");
}

void loop() {
  // read from port 1, send to port 0:
  if (Serial1.available()) {
    int inByte = Serial1.read();
    Serial.write(inByte);
  }

  // read from port 0, send to port 1:
  if (Serial.available()) {
    int inByte = Serial.read();
    //Serial.write(inByte);   //echo keyboard
    Serial1.write(inByte);
  }
}

connecting pins 2 and 3 to form a loopback test characters entered on Serial monitor are echoed back to the display

ESP32-C3 serial1  test Rx pin 3 Tx pin 2
   for loopback test connect pin 3 to pin 2
test 1 hello
test2 1234567890
test 3 !"£$%^&*()
test 4 abcdefghijklmnopqrstuvwxyz

could you try pins 2 and 3 for

MySerial0.begin(115200, 2, 3);

jackson_crawford · May 3, 2024, 7:51pm

I modified it and used this

#include <REG.h>
#include <wit_c_sdk.h>
#include <HardwareSerial.h>
#include <chrono>
#include <Arduino.h>

bool UP = false;
bool DOWN = false;
bool NEUTRAL = false;

bool neutralOccurred = false;

#define ACC_UPDATE		0x01
#define GYRO_UPDATE		0x02
#define ANGLE_UPDATE	0x04
#define MAG_UPDATE		0x08
#define READ_UPDATE		0x80
static volatile char s_cDataUpdate = 0, s_cCmd = 0xff; 

HardwareSerial MySerial0(0);

static void CmdProcess(void);
static void AutoScanSensor(void);
static void SensorUartSend(uint8_t *p_data, uint32_t uiSize);
static void SensorDataUpdata(uint32_t uiReg, uint32_t uiRegNum);
static void Delayms(uint16_t ucMs);
const uint32_t c_uiBaud[8] = {4800, 9600, 19200, 38400, 57600, 115200, 230400};


class Timer {
public:
    Timer() : m_running(false), m_elapsedTime(0) {}

    void start() {
        if (!m_running) {
            m_startTime = millis();
            m_running = true;
        }
    }

    void stop() {
        if (m_running) {
            m_elapsedTime += millis() - m_startTime;
            m_running = false;
        }
    }

    void reset() {
        m_elapsedTime = 0;
        m_running = false;
    }

    unsigned long getElapsedTime() const {
        if (m_running) {
            return m_elapsedTime + (millis() - m_startTime);
        } else {
            return m_elapsedTime;
        }
    }

private:
    bool m_running;
    unsigned long m_startTime;
    unsigned long m_elapsedTime; // in milliseconds
};

Timer timer;

//********************

void setup() {
  Serial.begin(9600);
  MySerial0.begin(115200, 2, 3);
	WitInit(WIT_PROTOCOL_NORMAL, 0x50);
	WitSerialWriteRegister(SensorUartSend);
	WitRegisterCallBack(SensorDataUpdata);
  WitDelayMsRegister(Delayms);
	Serial.print("\r\n********************** wit-motion normal example  ************************\r\n");
	AutoScanSensor();

}
int i;
float fAcc[3], fGyro[3], fAngle[3];
void loop() {
    
  while (MySerial0.available())
    {
      WitSerialDataIn(MySerial0.read());
    while (Serial.available())
    {
      CopeCmdData(Serial.read());
    }
    CmdProcess();
    if(s_cDataUpdate)
    {
      for(i = 0; i < 3; i++)
      {
        fAcc[i] = sReg[AX+i] / 32768.0f * 16.0f;
        fGyro[i] = sReg[GX+i] / 32768.0f * 2000.0f;
        fAngle[i] = sReg[Roll+i] / 32768.0f * 180.0f;
      }
      if(s_cDataUpdate & ACC_UPDATE)
      {
        Serial.print("acc:");
        Serial.print(fAcc[0], 3);
        Serial.print(" ");
        Serial.print(fAcc[1], 3);
        Serial.print(" ");
        Serial.print(fAcc[2], 3);
        Serial.print("\r\n");
        s_cDataUpdate &= ~ACC_UPDATE;
      }
      s_cDataUpdate = 0;
    }


    if (sqrt((fAcc[0]*fAcc[0])+(fAcc[1]*fAcc[1])+(fAcc[2]*fAcc[2])) > 1.05)
      {
        DOWN = true;
        UP = false;
        NEUTRAL = false;
        Serial.print("Down-");
      }
      if (sqrt((fAcc[0]*fAcc[0])+(fAcc[1]*fAcc[1])+(fAcc[2]*fAcc[2])) < .95)
      {
        UP = true;
        DOWN = false;
        NEUTRAL = false;
        Serial.print("Up+");
      }
      if (  (sqrt((fAcc[0]*fAcc[0])+(fAcc[1]*fAcc[1])+(fAcc[2]*fAcc[2])) < 1.05)  &&  (sqrt((fAcc[0]*fAcc[0])+(fAcc[1]*fAcc[1])+(fAcc[2]*fAcc[2])) > .95)  )
      {
        NEUTRAL = true;
        UP = false;
        DOWN = false;
        Serial.print("Neutral=");
      }
handleEvents(UP, NEUTRAL);
handleEvents2(DOWN, NEUTRAL);
Show();

    }
}


//*******************************

void handleEvents(bool UP, bool NEUTRAL) {
    static bool upDetected = false; // Flag to track if UP has been detected

    if (UP && !upDetected) {
        upDetected = true; // Set UP detected
    } else if (upDetected && NEUTRAL) {
        // If UP has been detected and NEUTRAL occurs, perform the action
        timer.stop();
        upDetected = false; // Reset UP detection
    } else if (!UP && NEUTRAL) {
        // If NEUTRAL occurs without UP, reset UP detection
        upDetected = false;
    }
}

//*******************************

void handleEvents2(bool DOWN, bool NEUTRAL) {
    static bool downDetected = false; // Flag to track if DOWN has been detected

    if (DOWN && !downDetected) {
        if (neutralOccurred) {
            // If DOWN event occurs after NEUTRAL, start the timer
            timer.reset();
        }
        downDetected = true; // Set DOWN detected
    } else if (downDetected && NEUTRAL) {
        // If DOWN has been detected and NEUTRAL occurs, perform the action
        timer.start();
        downDetected = false; // Reset DOWN detection
    }

    // Update the state of NEUTRAL event
    neutralOccurred = NEUTRAL;


}

void Show()
{
  Serial.print(timer.getElapsedTime());
  Serial.print(" , milliseconds  :   ");
  delay(50);
}

//******************************

void CopeCmdData(unsigned char ucData)
{
	static unsigned char s_ucData[50], s_ucRxCnt = 0;
	
	s_ucData[s_ucRxCnt++] = ucData;
	if(s_ucRxCnt<3)return;										//Less than three data returned
	if(s_ucRxCnt >= 50) s_ucRxCnt = 0;
	if(s_ucRxCnt >= 3)
	{
		if((s_ucData[1] == '\r') && (s_ucData[2] == '\n'))
		{
			s_cCmd = s_ucData[0];
			memset(s_ucData,0,50);
			s_ucRxCnt = 0;
		}
		else 
		{
			s_ucData[0] = s_ucData[1];
			s_ucData[1] = s_ucData[2];
			s_ucRxCnt = 2;
			
		}
	}
}

static void CmdProcess(void)
{
	switch(s_cCmd)
	{
		case 'a':	if(WitStartAccCali() != WIT_HAL_OK) Serial.print("\r\nSet AccCali Error\r\n");
			break;
		case 'm':	if(WitStartMagCali() != WIT_HAL_OK) Serial.print("\r\nSet MagCali Error\r\n");
			break;
		case 'e':	if(WitStopMagCali() != WIT_HAL_OK) Serial.print("\r\nSet MagCali Error\r\n");
			break;
		case 'u':	if(WitSetBandwidth(BANDWIDTH_5HZ) != WIT_HAL_OK) Serial.print("\r\nSet Bandwidth Error\r\n");
			break;
		case 'U':	if(WitSetBandwidth(BANDWIDTH_256HZ) != WIT_HAL_OK) Serial.print("\r\nSet Bandwidth Error\r\n");
			break;
		case 'B':	if(WitSetUartBaud(WIT_BAUD_115200) != WIT_HAL_OK) Serial.print("\r\nSet Baud Error\r\n");
              else 
              {
                MySerial0.begin(c_uiBaud[WIT_BAUD_115200]);
                Serial.print(" 115200 Baud rate modified successfully\r\n");
              }
			break;
		case 'b':	if(WitSetUartBaud(WIT_BAUD_9600) != WIT_HAL_OK) Serial.print("\r\nSet Baud Error\r\n");
              else 
              {
                MySerial0.begin(c_uiBaud[WIT_BAUD_9600]); 
                Serial.print(" 9600 Baud rate modified successfully\r\n");
              }
			break;
		case 'r': if(WitSetOutputRate(RRATE_1HZ) != WIT_HAL_OK)  Serial.print("\r\nSet Baud Error\r\n");
			        else Serial.print("\r\nSet Baud Success\r\n");
			break;
		case 'R':	if(WitSetOutputRate(RRATE_10HZ) != WIT_HAL_OK) Serial.print("\r\nSet Baud Error\r\n");
              else Serial.print("\r\nSet Baud Success\r\n");
			break;
    case 'C': if(WitSetContent(RSW_ACC|RSW_GYRO|RSW_ANGLE|RSW_MAG) != WIT_HAL_OK) Serial.print("\r\nSet RSW Error\r\n");
      break;
    case 'c': if(WitSetContent(RSW_ACC) != WIT_HAL_OK) Serial.print("\r\nSet RSW Error\r\n");
      break;
		default :break;
	}
	s_cCmd = 0xff;
}
static void SensorUartSend(uint8_t *p_data, uint32_t uiSize)
{
  MySerial0.write(p_data, uiSize);
  MySerial0.flush();
}
static void Delayms(uint16_t ucMs)
{
  delay(ucMs);
}
static void SensorDataUpdata(uint32_t uiReg, uint32_t uiRegNum)
{
	int i;
    for(i = 0; i < uiRegNum; i++)
    {
        switch(uiReg)
        {
            case AZ:
				s_cDataUpdate |= ACC_UPDATE;
            break;
            case GZ:
				s_cDataUpdate |= GYRO_UPDATE;
            break;
            case HZ:
				s_cDataUpdate |= MAG_UPDATE;
            break;
            case Yaw:
				s_cDataUpdate |= ANGLE_UPDATE;
            break;
            default:
				s_cDataUpdate |= READ_UPDATE;
			break;
        }
		uiReg++;
    }
}

static void AutoScanSensor(void)
{
	int i, iRetry;
	
	for(i = 0; i < sizeof(c_uiBaud)/sizeof(c_uiBaud[0]); i++)
	{
		MySerial0.begin(c_uiBaud[i]);
    MySerial0.flush();
		iRetry = 2;
		s_cDataUpdate = 0;
		do
		{
			WitReadReg(AX, 3);
			delay(200);
      while (MySerial0.available())
      {
        WitSerialDataIn(MySerial0.read());
      }
			if(s_cDataUpdate != 0)
			{
				Serial.print(c_uiBaud[i]);
				Serial.print(" baud find sensor\r\n\r\n");
				return ;
			}
			iRetry--;
		}while(iRetry);		
	}
	Serial.print("can not find sensor\r\n");
	Serial.print("please check your connection\r\n");
}

I changed the pins definition and it didn't seem to do anything I also tried switching the RX and TX pins as a sanity check and it didn't make a difference.
I just wanted some closure on whether or not I still needed to include the hardware serial:

HardwareSerial MySerial0(0);

And also I just wanted to be clear that this was a ESP32C3 XIAO seed studio not a ESP32C3 mini, I'm sure the chip is the same but I just was curious if the pins would be different as the pin definitions are labeled as 20 and 21 in the data-sheets:
xiao_esp32c3_pinout_top
And just for reference this is the WT901B:
download
Anyways am I doing something wrong or could my device be malfunctioning because it did work as it was but no matter what it is just not working.

I made that the ESP was outputting the sufficient 3.3 volts and it was.
I also checked if it was the sensor not sending data but it seemed like it was functioning properly.

jackson_crawford · May 3, 2024, 8:32pm

I realize now that In the programming I showed the TX and RX were swapped so I tried the other way but nothing.

horace · May 6, 2024, 4:36am

did you try the program of post 2 doing a simple loopback test?

can you give us a link to your WT901B Wit-Motion sensor

how have you connected and powered it?

upload a photo?

jackson_crawford · May 7, 2024, 10:07pm

Link for info Here
Link for product Here

I tried setting up the test but wasn't quite sure how I will try again but for clarification am I just supposed to switch "for loopback test connect pin 3 to pin 2" with whatever the test is going to be?

horace · May 8, 2024, 3:37pm

just to check Serial1 is working you connect pin 2 to pin 3 - characters entered on keyboard should be echoed back to the display
if OK remove link and connect
pin RXD1 3 to WT901B TX
pin TXD1 2 to WT901B RX

serial data from the WT901B should then appear on the serial monitor

jackson_crawford · May 9, 2024, 5:14pm

Ended up getting it working thanks, however what ended up working was pins 20 and 21 not 3 and 2. do you know what that's about?

// ESP32-C3-MINI-1 Serial1 test - for loopback test connect pins 2 and 3

// note GPIO20 U0RXD and GPIO21 U0TXD are used for Serial programming/debugging

#define RXD1 20
#define TXD1 21

void setup() {
  // initialize both serial ports:
  Serial.begin(115200);
  Serial1.begin(115200, SERIAL_8N1, RXD1, TXD1);
  Serial.println();
  Serial.println("\n\nESP32-C3 serial1  test Rx pin 3 Tx pin 2");
  //Serial.write("   for loopback test connect pin 3 to pin 2\n");
}

void loop() {
  // read from port 1, send to port 0:
  if (Serial1.available()) {
    int inByte = Serial1.read();
    Serial.write(inByte);
  }

  // read from port 0, send to port 1:
  if (Serial.available()) {
    int inByte = Serial.read();
    //Serial.write(inByte);   //echo keyboard
    Serial1.write(inByte);
  }
}

sakisdog · September 18, 2024, 10:17am

OMG! Thank you so much for this answer! I was trying to connect a GPS module to pins 20 21 that were the only two i had available on a Lolin C3 Mini board and i could not make it work.
Turned out i had to use Serial1.begin(9600, SERIAL_8N1, 20, 21) instead of Serial.begin(); (take note of the extra '1' next to word Serial)

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