Elechouse voice recognition module v3.1 on Arduino Mega

hakar99 · March 29, 2026, 12:29pm

Hello people,
I need help with setting up the Elechouse voice recognition module v3.1 on Arduino Mega.
I saw a few topics about this but I couldn't get to a solution.
my module works fine on an Uno board but doesn't work on Mega boards.
it keeps giving me "Check record failed or timeout." in the serial.
what is the issue?
I have also tried all possible pins, and have even changed the code to follow those pins but still nothing.
I will attach the connection and the code here for better understanding.
Thanks in advance.

/**
 ******************************************************************************
 * @file    vr_sample_train.ino
 * @author  JiapengLi
 * @brief   This file provides a demostration on 
 * how to train VoiceRecognitionModule to record your voice
 ******************************************************************************
 * @note:
 * Use serial command to control VoiceRecognitionModule. '
 * All commands are case insensitive. Default serial baud rate 115200.
 * 
 * COMMAND        FORMAT                        EXAMPLE                    Comment
 * 
 * train          train (r0) (r1)...            train 0 2 45               Train records
 * load           load (r0) (r1) ...            load 0 51 2 3              Load records
 * clear          clear                         clear                      remove all records in  Recognizer
 * record         record / record (r0) (r1)...  record / record 0 79       Check record train status
 * vr             vr                            vr                         Check recognizer status
 * getsig         getsig (r)                    getsig 0                   Get signature of record (r)
 * sigtrain       sigtrain (r) (sig)            sigtrain 0 ZERO            Train one record(r) with signature(sig)
 * settings       settings                      settings                   Check current system settings
 ******************************************************************************
 * @section  HISTORY
 * 
 * 2013/06/13    Initial version.
 */
#include <SoftwareSerial.h>
#include "VoiceRecognitionV3.h"

/**        
 * Connection
 * Arduino    VoiceRecognitionModule
 * 2   ------->     TX
 * 3   ------->     RX
 */
VR myVR(2,3);    // 2:RX 3:TX in the original code but I have tried almost all pins

/***************************************************************************/
/** declare print functions */
void printSeperator();
void printSignature(uint8_t *buf, int len);
void printVR(uint8_t *buf);
void printLoad(uint8_t *buf, uint8_t len);
void printTrain(uint8_t *buf, uint8_t len);
void printCheckRecognizer(uint8_t *buf);
void printUserGroup(uint8_t *buf, int len);
void printCheckRecord(uint8_t *buf, int num);
void printCheckRecordAll(uint8_t *buf, int num);
void printSigTrain(uint8_t *buf, uint8_t len);
void printSystemSettings(uint8_t *buf, int len);
void printHelp(void);

/***************************************************************************/
// command analyze part
#define CMD_BUF_LEN      64+1
#define CMD_NUM     10
typedef int (*cmd_function_t)(int, int);
uint8_t cmd[CMD_BUF_LEN];
uint8_t cmd_cnt;
uint8_t *paraAddr;
int receiveCMD();
int checkCMD(int len);
int checkParaNum(int len);
int findPara(int len, int paraNum, uint8_t **addr);
int compareCMD(uint8_t *para1 , uint8_t *para2, int len);

int cmdTrain(int len, int paraNum);
int cmdLoad(int len, int paraNum);
int cmdTest(int len, int paraNum);
int cmdVR(int len, int paraNum);
int cmdClear(int len, int paraNum);
int cmdRecord(int len, int paraNum);
int cmdSigTrain(int len, int paraNum);
int cmdGetSig(int len, int paraNum);
int cmdSettings(int len, int paraNum);
int cmdHelp(int len, int paraNum);
/** cmdList, cmdLen, cmdFunction has correspondence */
const char cmdList[CMD_NUM][10] = {  // command list table
  {
    "train"  }
  ,
  {
    "load"  }
  , 
  {
    "clear"  }
  ,
  {
    "vr"  }
  ,
  {
    "record"  }
  ,
  {
    "sigtrain"  }
  ,
  {
    "getsig"  }
  ,
  {
    "Settings"  }
  ,
  {
    "test"  }
  ,
  {
    "help"  }
  ,
};
const char cmdLen[CMD_NUM]= {    // command length
  5,  //  {"train"},
  4,  //  {"load"}, 
  5,  //  {"clear"},
  2,  //  {"vr"},
  6,  //  {"record"},
  8,  //  {"sigtrain"},
  6,  //  {"getsig"},
  8,  //  {"Settings"},
  4,  //  {"test"},
  4,  //  {"help"}
};
cmd_function_t cmdFunction[CMD_NUM]={      // command handle fuction(function pointer table)
  cmdTrain,
  cmdLoad,
  cmdClear,
  cmdVR,
  cmdRecord,
  cmdSigTrain,
  cmdGetSig,
  cmdSettings,
  cmdTest,
  cmdHelp,
};

/***************************************************************************/
/** temprory data */
uint8_t buf[255];
uint8_t records[7]; // save record

void setup(void)
{
  myVR.begin(9600);

  /** initialize */
  Serial.begin(115200);
  Serial.println(F("Elechouse Voice Recognition V3 Module \"train\" sample."));

  printSeperator();
  Serial.println(F("Usage:"));
  printSeperator();
  printHelp();
  printSeperator();
  cmd_cnt = 0;
}

void loop(void)
{
  int len, paraNum, paraLen, i;

  /** receive Serial command */
  len = receiveCMD();
  if(len>0){
    /** check if the received command is valid */
    if(!checkCMD(len)){

      /** check parameter number of the received command  */
      paraNum = checkParaNum(len);

      /** display the receved command back */
      Serial.write(cmd, len);

      /** find the first parameter */
      paraLen = findPara(len, 1, &paraAddr);

      /** compare the received command with command in the list */
      for(i=0; i<CMD_NUM; i++){
        /** compare command length */
        if(paraLen == cmdLen[i]){
          /** compare command content */
          if( compareCMD(paraAddr, (uint8_t *)cmdList[i], paraLen) == 0 ){
            /** call command function */
            if( cmdFunction[i](len, paraNum) != 0){
              printSeperator();
              Serial.println(F("Command Format Error!"));
              printSeperator();
            }
            break;
          }
        }
      }

      /** command is not supported*/
      if(i == CMD_NUM){ 
        printSeperator();
        Serial.println(F("Unkonwn command"));
        printSeperator();
      }
    }
    else{
      /** received command is invalid */
      printSeperator();
      Serial.println(F("Command format error"));
      printSeperator();
    }
  }

  /** try to receive recognize result */
  int ret;
  ret = myVR.recognize(buf, 50);
  if(ret>0){
    /** voice recognized, print result */
    printVR(buf);
  }
}

/**
 * @brief   receive command from Serial.
 * @param   NONE.
 * @retval  command length, if no command receive return -1.
 */
int receiveCMD()
{
  int ret;
  int len;
  unsigned long start_millis;
  start_millis = millis();
  while(1){
    ret = Serial.read();
    if(ret>0){
      start_millis = millis();
      cmd[cmd_cnt] = ret;
      if(cmd[cmd_cnt] == '\n'){
        len = cmd_cnt+1;
        cmd_cnt = 0;
        return len;
      }
      cmd_cnt++;
      if(cmd_cnt == CMD_BUF_LEN){
        cmd_cnt = 0;
        return -1;
      }
    }

    if(millis() - start_millis > 100){
      cmd_cnt = 0;
      return -1;
    }
  }
}

/**
 * @brief   compare two commands, case insensitive.
 * @param   para1  -->  command buffer 1
 * para2  -->  command buffer 2
 * len    -->  buffer length
 * @retval  0  --> equal
 * -1  --> unequal
 */
int compareCMD(uint8_t *para1 , uint8_t *para2, int len)
{
  int i;
  uint8_t res;
  for(i=0; i<len; i++){
    res = para2[i] - para1[i];
    if(res != 0 && res != 0x20){
      res = para1[i] - para2[i];
      if(res != 0 && res != 0x20){
        return -1;
      }
    }
  }
  return 0;
}

/**
 * @brief   Check command format.
 * @param   len  -->  command length
 * @retval  0  -->  command is valid
 * -1  -->  command is invalid
 */
int checkCMD(int len)
{
  int i;
  for(i=0; i<len; i++){
    if(cmd[i] > 0x1F && cmd[i] < 0x7F){

    }
    else if(cmd[i] == '\t' || cmd[i] == ' ' || cmd[i] == '\r' || cmd[i] == '\n'){

    }
    else{
      return -1;
    }
  }
  return 0;
}

/**
 * @brief   Check the number of parameters in the command
 * @param   len  -->  command length
 * @retval  number of parameters
 */
int checkParaNum(int len)
{
  int cnt=0, i;
  for(i=0; i<len; ){
    if(cmd[i]!='\t' && cmd[i]!=' ' && cmd[i] != '\r' && cmd[i] != '\n'){
      cnt++;
      while(cmd[i] != '\t' && cmd[i] != ' ' && cmd[i] != '\r' && cmd[i] != '\n'){
        i++;
      }
    }
    i++;
  }
  return cnt;
}

/**
 * @brief   Find the specified parameter.
 * @param   len       -->  command length
 * paraIndex -->  parameter index
 * addr      -->  return value. position of the parameter
 * @retval  length of specified parameter
 */
int findPara(int len, int paraIndex, uint8_t **addr)
{
  int cnt=0, i, paraLen;
  uint8_t dt;
  for(i=0; i<len; ){
    dt = cmd[i];
    if(dt!='\t' && dt!=' '){
      cnt++;
      if(paraIndex == cnt){
        *addr = cmd+i;
        paraLen = 0;
        while(cmd[i] != '\t' && cmd[i] != ' ' && cmd[i] != '\r' && cmd[i] != '\n'){
          i++;
          paraLen++;
        }
        return paraLen;
      }
      else{
        while(cmd[i] != '\t' && cmd[i] != ' ' && cmd[i] != '\r' && cmd[i] != '\n'){
          i++;
        }
      }
    }
    else{
      i++;
    }
  }
  return -1;
}

int cmdHelp(int len, int paraNum)
{
  if(paraNum != 1){
    return -1;
  }
  printSeperator();
  printHelp();
  printSeperator();
  return 0;
}

/**
 * @brief   Handle "train" command
 * @param   len     --> command length
 * paraNum --> number of parameters
 * @retval  0 --> success
 * -1 --> Command format error
 */
int cmdTrain(int len, int paraNum)
{
  int i, ret;
  if(paraNum < 2 || paraNum > 8 ){
    return -1;
  }

  for(i=2; i<=paraNum; i++){
    findPara(len, i, &paraAddr);
    records[i-2] = atoi((char *)paraAddr);
    if(records[i-2] == 0 && *paraAddr != '0'){
      return -1;
    }
  }
  printSeperator();
  ret = myVR.train(records, paraNum-1, buf);
  //  ret = myVR.train(records, paraNum-1);
  if(ret >= 0){
    printTrain(buf, ret);
  }
  else if(ret == -1){
    Serial.println(F("Train failed."));
  }
  else if(ret == -2){
    Serial.println(F("Train Timeout."));
  }
  printSeperator();
  return 0;
}

/**
 * @brief   Handle "load" command
 * @param   len     --> command length
 * paraNum --> number of parameters
 * @retval  0 --> success
 * -1 --> Command format error
 */
int cmdLoad(int len, int paraNum)
{
  int i, ret;
  if(paraNum < 2 || paraNum > 8 ){
    return -1;
  }

  for(i=2; i<=paraNum; i++){
    findPara(len, i, &paraAddr);
    records[i-2] = atoi((char *)paraAddr);
    if(records[i-2] == 0 && *paraAddr != '0'){
      return -1;
    }
  }
  //  myVR.writehex(records, paraNum-1);
  ret = myVR.load(records, paraNum-1, buf);
  printSeperator();
  if(ret >= 0){
    printLoad(buf, ret);
  }
  else{
    Serial.println(F("Load failed or timeout."));
  }
  printSeperator();
  return 0;
}

/**
 * @brief   Handle "clear" command
 * @param   len     --> command length
 * paraNum --> number of parameters
 * @retval  0 --> success
 * -1 --> Command format error
 */
int cmdClear(int len, int paraNum)
{
  if(paraNum != 1){
    return -1;
  }
  if(myVR.clear() == 0){
    printSeperator();
    Serial.println(F("Recognizer cleared."));
    printSeperator();
  }
  else{
    printSeperator();
    Serial.println(F("Clear recognizer failed or timeout."));
    printSeperator();
  }
  return 0;
}

/**
 * @brief   Handle "vr" command
 * @param   len     --> command length
 * paraNum --> number of parameters
 * @retval  0 --> success
 * -1 --> Command format error
 */
int cmdVR(int len, int paraNum)
{
  int ret;
  if(paraNum != 1){
    return -1;
  }
  ret = myVR.checkRecognizer(buf);
  if(ret<=0){
    printSeperator();
    Serial.println(F("Check recognizer failed or timeout."));
    printSeperator();
    return 0;
  }
  printSeperator();
  printCheckRecognizer(buf);
  printSeperator();
  return 0;
}

/**
 * @brief   Handle "record" command
 * @param   len     --> command length
 * paraNum --> number of parameters
 * @retval  0 --> success
 * -1 --> Command format error
 */
int cmdRecord(int len, int paraNum)
{
  int ret;
  if(paraNum == 1){
    ret = myVR.checkRecord(buf);
    printSeperator();
    if(ret>=0){
      printCheckRecordAll(buf, ret);
    }
    else{
      Serial.println(F("Check record failed or timeout."));
    }
    printSeperator();
  }
  else if(paraNum < 9){
    for(int i=2; i<=paraNum; i++){
      findPara(len, i, &paraAddr);
      records[i-2] = atoi((char *)paraAddr);
      if(records[i-2] == 0 && *paraAddr != '0'){
        return -1;
      }      
    }

    ret = myVR.checkRecord(buf, records, paraNum-1);    // auto clean duplicate records
    printSeperator();
    if(ret>=0){
      printCheckRecord(buf, ret);
    }
    else{
      Serial.println(F("Check record failed or timeout."));
    }
    printSeperator();
  }
  else{
    return -1;
  }
  return 0;
}

/**
 * @brief   Handle "sigtrain" command
 * @param   len     --> command length
 * paraNum --> number of parameters
 * @retval  0 --> success
 * -1 --> Command format error
 */
int cmdSigTrain(int len, int paraNum)
{
  int ret, sig_len;
  uint8_t *lastAddr;
  if(paraNum < 2){
    return -1;
  }

  findPara(len, 2, &paraAddr);
  records[0] = atoi((char *)paraAddr);
  if(records[0] == 0 && *paraAddr != '0'){
    return -1;
  }

  findPara(len, 3, &paraAddr);
  sig_len = findPara(len, paraNum, &lastAddr);
  sig_len +=( (unsigned int)lastAddr - (unsigned int)paraAddr );

  printSeperator();
  ret = myVR.trainWithSignature(records[0], paraAddr, sig_len, buf);
  //  ret = myVR.trainWithSignature(records, paraNum-1);
  if(ret >= 0){
    printSigTrain(buf, ret);
  }
  else{
    Serial.println(F("Train with signature failed or timeout."));
  }
  printSeperator();

  return 0;
}

/**
 * @brief   Handle "getsig" command
 * @param   len     --> command length
 * paraNum --> number of parameters
 * @retval  0 --> success
 * -1 --> Command format error
 */
int cmdGetSig(int len, int paraNum)
{
  int ret;
  if(paraNum != 2){
    return -1;
  }

  findPara(len, 2, &paraAddr);
  records[0] = atoi((char *)paraAddr);
  if(records[0] == 0 && *paraAddr != '0'){
    return -1;
  }

  ret = myVR.checkSignature(records[0], buf);

  printSeperator();
  if(ret == 0){
    Serial.println(F("Signature isn't set."));
  }
  else if(ret > 0){
    Serial.print(F("Signature:"));
    printSignature(buf, ret);
    Serial.println();
  }
  else{
    Serial.println(F("Get sig error or timeout."));
  }
  printSeperator();

  return 0;
}

/**
 * @brief   Handle "test" command
 * @param   len     --> command length
 * paraNum --> number of parameters
 * @retval  0 --> success
 * -1 --> Command format error
 */
int cmdTest(int len, int paraNum)
{
  printSeperator();
  Serial.println(F("TEST is not supported."));
  printSeperator();
  return 0;
}

int cmdSettings(int len, int paraNum)
{
  int ret;
  if(paraNum != 1){
    return -1;
  }
  ret = myVR.checkSystemSettings(buf);
  if( ret > 0){
    printSeperator();
    printSystemSettings(buf, ret);
    printSeperator();
  }
  else{
    printSeperator();
    Serial.println(F("Check system settings error or timeout"));
    printSeperator();
  }
  return 0;
}

/*****************************************************************************/
/**
 * @brief   Print signature, if the character is invisible, 
 * print hexible value instead.
 * @param   buf     --> command length
 * len     --> number of parameters
 */
void printSignature(uint8_t *buf, int len)
{
  int i;
  for(i=0; i<len; i++){
    if(buf[i]>0x19 && buf[i]<0x7F){
      Serial.write(buf[i]);
    }
    else{
      Serial.print(F("["));
      Serial.print(buf[i], HEX);
      Serial.print(F("]"));
    }
  }
}

/**
 * @brief   Print signature, if the character is invisible, 
 * print hexible value instead.
 * @param   buf  -->  VR module return value when voice is recognized.
 * buf[0]  -->  Group mode(FF: None Group, 0x8n: User, 0x0n:System
 * buf[1]  -->  number of record which is recognized. 
 * buf[2]  -->  Recognizer index(position) value of the recognized record.
 * buf[3]  -->  Signature length
 * buf[4]~buf[n] --> Signature
 */
void printVR(uint8_t *buf)
{
  Serial.println(F("VR Index\tGroup\tRecordNum\tSignature"));

  Serial.print(buf[2], DEC);
  Serial.print(F("\t\t"));

  if(buf[0] == 0xFF){
    Serial.print(F("NONE"));
  }
  else if(buf[0]&0x80){
    Serial.print(F("UG "));
    Serial.print(buf[0]&(~0x80), DEC);
  }
  else{
    Serial.print(F("SG "));
    Serial.print(buf[0], DEC);
  }
  Serial.print(F("\t"));

  Serial.print(buf[1], DEC);
  Serial.print(F("\t\t"));
  if(buf[3]>0){
    printSignature(buf+4, buf[3]);
  }
  else{
    Serial.print(F("NONE"));
  }
  Serial.println(F("\r\n"));
}

/**
 * @brief   Print seperator. Print 80 '-'.
 */
void printSeperator()
{
  for(int i=0; i<80; i++){
    Serial.write('-');
  }
  Serial.println();
}

/**
 * @brief   Print recoginizer status.
 * @param   buf  -->  VR module return value when voice is recognized.
 * buf[0]     -->  Number of valid voice records in recognizer
 * buf[i+1]   -->  Record number.(0xFF: Not loaded(Nongroup mode), or not set (Group mode)) (i= 0, 1, ... 6)
 * buf[8]     -->  Number of all voice records in recognizer
 * buf[9]     -->  Valid records position indicate.
 * buf[10]    -->  Group mode indicate(FF: None Group, 0x8n: User, 0x0n:System)
 */
void printCheckRecognizer(uint8_t *buf)
{
  Serial.print(F("All voice records in recognizer: "));
  Serial.println(buf[8], DEC);
  Serial.print(F("Valid voice records in recognizer: "));
  Serial.println(buf[0], DEC);
  if(buf[10] == 0xFF){
    Serial.println(F("VR is not in group mode."));
  }
  else if(buf[10]&0x80){
    Serial.print(F("VR is in user group mode:"));
    Serial.println(buf[10]&0x7F, DEC);
  }
  else{
    Serial.print(F("VR is in system group mode:"));
    Serial.println(buf[10], DEC);
  }
  Serial.println(F("VR Index\tRecord\t\tComment"));
  for(int i=0; i<7; i++){
    Serial.print(i, DEC);
    Serial.print(F("\t\t"));
    if(buf[i+1] == 0xFF){
      if(buf[10] == 0xFF){
        Serial.print(F("Unloaded\tNONE"));
      }
      else{
        Serial.print(F("Not Set\t\tNONE"));
      }
    }
    else{
      Serial.print(buf[i+1], DEC);
      Serial.print(F("\t\t"));
      if(buf[9]&(1<<i)){
        Serial.print(F("Valid"));
      }
      else{
        Serial.print(F("Untrained"));
      }
    }

    Serial.println();
  } 
}

/**
 * @brief   Print record train status.
 * @param   buf  -->  Check record command return value
 * buf[0]     -->  Number of checked records
 * buf[2i+1]  -->  Record number.
 * buf[2i+2]  -->  Record train status. (00: untrained, 01: trained, FF: record value out of range)
 * (i = 0 ~ buf[0]-1 )
 * num  -->  Number of trained records
 */
void printCheckRecord(uint8_t *buf, int num)
{
  Serial.print(F("Check "));
  Serial.print(buf[0], DEC);
  Serial.println(F(" records."));

  Serial.print(num, DEC);
  if(num>1){
    Serial.println(F(" records trained."));
  }
  else{
    Serial.println(F(" record trained."));
  }

  for(int i=0; i<buf[0]*2; i += 2){
    Serial.print(buf[i+1], DEC);
    Serial.print(F("\t-->\t"));
    switch(buf[i+2]){
    case 0x01:
      Serial.print(F("Trained"));
      break;
    case 0x00:
      Serial.print(F("Untrained"));
      break;
    case 0xFF:
      Serial.print(F("Record value out of range"));
      break;
    default:
      Serial.print(F("Unknown Stauts"));
      break;
    }
    Serial.println();
  }
}

/**
 * @brief   Print record train status.
 * @param   buf  -->  Check record command return value
 * buf[0]     -->  Number of checked records
 * buf[2i+1]  -->  Record number.
 * buf[2i+2]  -->  Record train status. (00: untrained, 01: trained, FF: record value out of range)
 * (i = 0 ~ buf[0]-1 )
 * num  -->  Number of trained records
 */
void printCheckRecordAll(uint8_t *buf, int num)
{
  Serial.print(F("Check 255"));
  Serial.println(F(" records."));

  Serial.print(num, DEC);
  if(num>1){
    Serial.println(F(" records trained."));
  }
  else{
    Serial.println(F(" record trained."));
  }
  myVR.writehex(buf, 255);
  for(int i=0; i<255; i++){
    if(buf[i] == 0xF0){
      continue;
    }
    Serial.print(i, DEC);
    Serial.print(F("\t-->\t"));
    switch(buf[i]){
    case 0x01:
      Serial.print(F("Trained"));
      break;
    case 0x00:
      Serial.print(F("Untrained"));
      break;
    case 0xFF:
      Serial.print(F("Record value out of range"));
      break;
    default:
      Serial.print(F("Unknown Stauts"));
      break;
    }
    Serial.println();
  }
}

/**
 * @brief   Print check user group result.
 * @param   buf  -->  Check record command return value
 * buf[8i]    -->  group number.
 * buf[8i+1]  -->  group position 0 status.
 * buf[8i+2]  -->  group position 1 status.
 * ...                ...
 * buf[8i+6]  -->  group position 5 status.
 * buf[8i+7]  -->  group position 6 status.
 * (i = 0 ~ len)
 * len  -->  number of checked groups
 */
void printUserGroup(uint8_t *buf, int len)
{
  int i, j;
  Serial.println(F("Check User Group:"));
  for(i=0; i<len; i++){
    Serial.print(F("Group:"));
    Serial.println(buf[8*i]);
    for(j=0; j<7; j++){
      if(buf[8*i+1+j] == 0xFF){
        Serial.print(F("NONE\t"));
      }
      else{
        Serial.print(buf[8*i+1+j], DEC);
        Serial.print(F("\t"));
      }
    }
    Serial.println();
  }
}

/**
 * @brief   Print "load" command return value.
 * @param   buf  -->  "load" command return value
 * buf[0]    -->  number of records which are load successfully.
 * buf[2i+1]  -->  record number
 * buf[2i+2]  -->  record load status.
 * 00 --> Loaded 
 * FC --> Record already in recognizer
 * FD --> Recognizer full
 * FE --> Record untrained
 * FF --> Value out of range"
 * (i = 0 ~ (len-1)/2 )
 * len  -->  length of buf
 */
void printLoad(uint8_t *buf, uint8_t len)
{
  if(len == 0){
    Serial.println(F("Load Successfully."));
    return;
  }
  else{
    Serial.print(F("Load success: "));
    Serial.println(buf[0], DEC);
  }
  for(int i=0; i<len-1; i += 2){
    Serial.print(F("Record "));
    Serial.print(buf[i+1], DEC);
    Serial.print(F("\t"));
    switch(buf[i+2]){
    case 0:
      Serial.println(F("Loaded"));
      break;
    case 0xFC:
      Serial.println(F("Record already in recognizer"));
      break;
    case 0xFD:
      Serial.println(F("Recognizer full"));
      break;
    case 0xFE:
      Serial.println(F("Record untrained"));
      break;
    case 0xFF:
      Serial.println(F("Value out of range"));
      break;
    default:
      Serial.println(F("Unknown status"));
      break;
    }
  }
}

/**
 * @brief   Print "train" command return value.
 * @param   buf  -->  "train" command return value
 * buf[0]    -->  number of records which are trained successfully.
 * buf[2i+1]  -->  record number
 * buf[2i+2]  -->  record train status.
 * 00 --> Trained 
 * FE --> Train Time Out
 * FF --> Value out of range"
 * (i = 0 ~ len-1 )
 * len  -->  length of buf
 */
void printTrain(uint8_t *buf, uint8_t len)
{
  if(len == 0){
    Serial.println(F("Train Finish."));
    return;
  }
  else{
    Serial.print(F("Train success: "));
    Serial.println(buf[0], DEC);
  }
  for(int i=0; i<len-1; i += 2){
    Serial.print(F("Record "));
    Serial.print(buf[i+1], DEC);
    Serial.print(F("\t"));
    switch(buf[i+2]){
    case 0:
      Serial.println(F("Trained"));
      break;
    case 0xFE:
      Serial.println(F("Train Time Out"));
      break;
    case 0xFF:
      Serial.println(F("Value out of range"));
      break;
    default:
      Serial.print(F("Unknown status "));
      Serial.println(buf[i+2], HEX);
      break;
    }
  }
}

/**
 * @brief   Print "sigtrain" command return value.
 * @param   buf  -->  "sigtrain" command return value
 * buf[0]  -->  number of records which are trained successfully.
 * buf[1]  -->  record number
 * buf[2]  -->  record train status.
 * 00 --> Trained 
 * F0 --> Trained, signature truncate
 * FE --> Train Time Out
 * FF --> Value out of range"
 * buf[3] ~ buf[len-1] --> Signature.
 * len  -->  length of buf
 */
void printSigTrain(uint8_t *buf, uint8_t len)
{
  if(len == 0){
    Serial.println(F("Train With Signature Finish."));
    return;
  }
  else{
    Serial.print(F("Success: "));
    Serial.println(buf[0], DEC);
  }
  Serial.print(F("Record "));
  Serial.print(buf[1], DEC);
  Serial.print(F("\t"));
  switch(buf[2]){
  case 0:
    Serial.println(F("Trained"));
    break;
  case 0xF0:
    Serial.println(F("Trained, signature truncate"));
    break;
  case 0xFE:
    Serial.println(F("Train Time Out"));
    break;
  case 0xFF:
    Serial.println(F("Value out of range"));
    break;
  default:
    Serial.print(F("Unknown status "));
    Serial.println(buf[2], HEX);
    break;
  }
  Serial.print(F("SIG: "));
  Serial.write(buf+3, len-3);
  Serial.println();
}

/**
 * @brief   Print "settings" command return value.
 * @param   buf  -->  "settings" command return value
 * buf[0]  -->  number of records which are trained successfully.
 * buf[1]  -->  record number
 * buf[2]  -->  record train status.
 * 00 --> Trained 
 * F0 --> Trained, signature truncate
 * FE --> Train Time Out
 * FF --> Value out of range"
 * buf[3] ~ buf[len-1] --> Signature.
 * len  -->  length of buf
 */

const unsigned int io_pw_tab[16]={
  10,  15,  20,  25,  30,  35,  40,  45, 
  50,  75,  100, 200, 300, 400, 500, 1000
};

void printSystemSettings(uint8_t *buf, int len)
{

  switch(buf[0]){
  case 0:
  case 3:
    Serial.println(F("Baud rate: 9600"));
    break;
  case 1:
    Serial.println(F("Baud rate: 2400"));
    break;
  case 2:
    Serial.println(F("Baud rate: 4800"));
    break;
  case 4:
    Serial.println(F("Baud rate: 19200"));
    break;
  case 5:
    Serial.println(F("Baud rate: 38400"));
    break;
  default:
    Serial.println(F("Baud rate: UNKONOWN"));
    break;
  }

  switch(buf[1]){
  case 0:
  case 0xFF:
    Serial.println(F("Outpu IO Mode: Pulse"));
    break;
  case 1:
    Serial.println(F("Outpu IO Mode: Toggle"));
    break;
  case 2:
    Serial.println(F("Outpu IO Mode: Clear(When recognized) "));
    break;
  case 3:
    Serial.println(F("Outpu IO Mode: Set(When recognized)"));
    break;
  default:
    Serial.println(F("Output IO Mode: UNKONOWN"));
    break;
  }

  if(buf[2] > 15){
    Serial.println(F("Pulse width: UNKONOWN"));
  }
  else{
    Serial.print(F("Pulse Width: "));
    Serial.print(io_pw_tab[buf[2]], DEC);
    Serial.println(F("ms"));
  }

  if(buf[3] == 0 || buf[3] == 0xFF){
    Serial.println(F("Auto Load: disable"));
  }
  else{
    Serial.println(F("Auto Load: enable"));
  }

  switch(buf[4]){
  case 0:
  case 0xFF:
    Serial.println(F("Group control by external IO: disabled"));
    break;
  case 1:
    Serial.println(F("Group control by external IO: system group selected"));
    break;
  case 2:
    Serial.println(F("Group control by external IO: user group selected"));
    break;
  default:
    Serial.println(F("Group control by external IO: UNKNOWN STATUS"));
    break;
  }
}

void printHelp(void)
{
  Serial.println(F("COMMAND        FORMAT                        EXAMPLE                    Comment"));
  printSeperator();
  //  Serial.println(F("--------------------------------------------------------------------------------------------------------------"));
  Serial.println(F("train          train (r0) (r1)...            train 0 2 45               Train records"));
  Serial.println(F("load           load (r0) (r1) ...            load 0 51 2 3              Load records"));
  Serial.println(F("clear          clear                         clear                      remove all records in  Recognizer"));
  Serial.println(F("record         record / record (r0) (r1)...  record / record 0 79       Check record train status"));
  Serial.println(F("vr             vr                            vr                         Check recognizer status"));
  Serial.println(F("getsig         getsig (r)                    getsig 0                   Get signature of record (r)"));
  Serial.println(F("sigtrain       sigtrain (r) (sig)            sigtrain 0 ZERO            Train one record(r) with signature(sig)"));
  Serial.println(F("settings       settings                      settings                   Check current system settings"));
  Serial.println(F("help           help                          help                       print this message"));
}

applebanna648 · March 29, 2026, 12:56pm

The issue is that on the Arduino Mega, Pin 3 does not support RX when using the SoftwareSerial library. Only specific pins on the Mega can be used for RX (10, 11, 12, 13, 14, 15, 50, 51, 52, 53, and A8-A15), as mentioned here

Move your module's TX wire to Mega Pin 10.
Move your module's RX wire to Mega Pin 11.
Change your code to: VR myVR(10, 11);

Alternatively, since the Mega has multiple hardware serial ports, you should consider using Serial1 (Pins 18/19) instead of SoftwareSerial for much better reliability.

xfpd · March 29, 2026, 1:04pm

Using the same error in more than one place in the sketch makes troubleshooting more difficult.

In reading this about SoftwareSerial library: https://docs.arduino.cc/learn/built-in-libraries/software-serial/

Not all pins on the Mega and Mega 2560 boards support change interrupts, so only the following can be used for RX: 10, 11, 12, 13, 14, 15, 50, 51, 52, 53, A8 (62), A9 (63), A10 (64), A11 (65), A12 (66), A13 (67), A14 (68), A15 (69)

hakar99 · April 5, 2026, 1:43pm

after changing the pin locations. no improvement was done unfortunately.
now, the module's TX wire is connected to Mega's Pin 10.
the module's RX wire is connected to Mega Pin 11.
the code is also changed to VR myVR(10, 11);
I even went and bought another voice module and Mega board but still nothing, same exact error.

hakar99 · April 5, 2026, 1:46pm

understandable, but this is the original setup code from the library itself.
I tried a few of these pins here but nothing worked.

Not all pins on the Mega and Mega 2560 boards support change interrupts, so only the following can be used for RX: 10, 11, 12, 13, 14, 15, 50, 51, 52, 53, A8 (62), A9 (63), A10 (64), A11 (65), A12 (66), A13 (67), A14 (68), A15 (69)

should I just call it quits and forget it?

xfpd · April 5, 2026, 3:59pm

The documentation I read (the manual and the library) shows the Uno R3 using SoftwareSerial with Pin 2 and Pin 3. Both manual and library show how to test the module with just a terminal and a comm port.

You did not write if "almost all pins" test good or bad.

I will guess "bad." Verify you have "rx/tx" connected correctly. Perhaps not important, but Uno R3 pins 2 and 3 can also generate interrupts. I would test the Uno R3 using SoftwareSerial using any pair of pins other than 2/3. If this fails to connect, then I would guess interrupts are mandatory. If that is true, I would test just Pin 2 (with any pin for TX) for pass/fail, and if that fails I would test just pin 3 (with any pin for RX) for pass/fail. This should determine if interrupts are needed.

And... the last thing in the world I would ever do is buy a "speech" product from a company that can't spell it correctly... and not just once.

jremington · April 5, 2026, 4:02pm

Use one of the four hardware serial ports on the Mega, instead of software serial.

hakar99 · April 5, 2026, 4:19pm

I bought from a local store here that sells arduino things. did not know they misspelled a bunch of words.
I will look for something else I guess, or try to connect the uno board to the mega board as a last resort.

xfpd · April 5, 2026, 4:46pm

This statement is confusing... and makes me wonder if more has been done incorrectly. Try the experiments I mentioned above.

jremington · April 5, 2026, 4:46pm

You could also try reading post #8, and following the suggestion. As suggested in post #3 as well.

hakar99 · April 6, 2026, 4:47pm

I meant to connect the voice module to the uno since it works fine.
then connect the uno board to the mega board some how.
it will complicate things more but I have to make the mega board work somehow.

xfpd · April 6, 2026, 4:53pm

Please, show each of the above suggestions and the results you found.

jremington · April 6, 2026, 4:54pm

The obvious way to do that is to use hardware serial on the Mega.

But perhaps you should choose simpler projects and learn a bit more about how Arduinos work, before attempting this slightly more difficult challenge.

hakar99 · April 7, 2026, 4:32pm

okay, after tampering with the library for a while, I got it to work.
the hardware suggestion did work, but not with the regular library.
thanks everyone, this was a relief indeed

xfpd · April 7, 2026, 4:36pm

What is your final hardware and library configuration? Would you supply a drawing and the code?

hakar99 · April 9, 2026, 5:45pm

am I allowed to share the modified library?
will I not get sued by the original author?

jremington · April 9, 2026, 6:54pm

Arduino is open source and resources are shared. Feel free to post the modified library.

Topic		Replies	Views
Voice recognition module V3.1 General Guidance	19	160	April 23, 2026
Voice recognition module with mega arduino 2560 General Guidance	20	1019	August 24, 2024
Voice module recognition v3 to arduino mega 2560 General Guidance	5	468	January 12, 2025
Error de timeout al ejecutar comando en Modulo de reconocimiento de Voz con Arduino Mega 2560 Español	5	130	April 22, 2025
Interface ELECHOUSE Speech Recognition Module V3 using arduino uno General Guidance	1	83	October 9, 2025

Elechouse voice recognition module v3.1 on Arduino Mega

Related topics