Nano resets or freezes on calling a function

Question

I'm controlling a light bulb with my Arduino Nano from serial or RF (via nRF24L01+) and I'm passing the commands as a string. After I get all the variables (3 ints) I try calling the function execOrder but no matter what I put in there, the Arduino just hangs or resets. Code is as follows:

#define SSR 3
#define SW 4
#define nanoID 1
bool isPWM = false;
int value;

// Módulo RF
#include <SPI.h>
#include "nRF24L01.h"
#include "RF24.h"
#include "printf.h"
RF24 radio(9,10);
const uint64_t pipes[2] = { 0xF0F0F0F0E1LL, 0xF0F0F0F0D2LL };
#define PayLoad 20

#include <MemoryFree.h>

void setup() {
  pinMode(SSR, OUTPUT);
  pinMode(SW, INPUT_PULLUP);
  digitalWrite(SSR, LOW);
  value = 0;
  Serial.begin(9600);
  Serial.println("------ CEACI SAS -- Controller Module ------");
  Serial.println("Module No: " + String(nanoID));
  // Inicializar RF
  Serial.println("Inicializando RF");
  radio.begin();
  radio.setRetries(15,15);
  radio.setPayloadSize(PayLoad);
  radio.setPALevel(RF24_PA_MIN);
  radio.setDataRate(RF24_250KBPS);
  radio.setCRCLength(RF24_CRC_16);
  delay(100);
  radio.openWritingPipe(pipes[1]);
  radio.openReadingPipe(1,pipes[0]);
  radio.startListening();
  //radio.printDetails(); //RF Debug
  Serial.println("RF listo!");
  Serial.print("freeMemory()=");
  Serial.println(freeMemory());
}

void loop() {
  if (Serial.available()) {
    Serial.println("Rcvd Serial!");
    String msgRcvd = Serial.readString();
    int ID = msgRcvd.substring(4,5).toInt();
    int cmdCode = msgRcvd.substring(10,11).toInt();
    int cmdVal = msgRcvd.substring(16).toInt();
    //Serial.println("ID: "+String(ID)+", CMD: "+String(cmdCode)+", VAL: "+String(cmdVal));
    Serial.print("freeMemory()=");
    Serial.println(freeMemory());
    //execOrder(ID,cmdCode,cmdVal);
  } else if (radio.available()){
    int RFlen=0;
    char msgBuff[]="";
    RFlen = radio.getDynamicPayloadSize();
    delay(10);
    radio.read(&msgBuff, RFlen);
    String msgRcvd(msgBuff);
    int ID = msgRcvd.substring(4,5).toInt();
    int cmdCode = msgRcvd.substring(10,11).toInt();
    int cmdVal = msgRcvd.substring(16).toInt();
    //Serial.println("ID: "+String(ID)+", CMD: "+String(cmdCode)+", VAL: "+String(cmdVal));
    Serial.print("freeMemory()=");
    Serial.println(freeMemory());
    //execOrder(ID,cmdCode,cmdVal);
  } else {
    chkSwitch();
  }
}

void execOrder(int ID, int CMD, int VAL){
  if (ID == nanoID || ID == 0){
    switch(CMD){
      case 0:
        State();
        break;
      case 1:
        value = VAL;
        OnOff();
        break;
      case 2:
        value = VAL;
        PWM();
        break;
    }
  }
}

I wanted to process the incoming string in a function, but it resets as well.

By the way, I'm using MemoryFree library to check if I'm out of memory, and there's plenty of it, so I don't really know where's the problem. Any help would be greatly appreciated!

EDIT:

For the serial part I can do the following (my original code):

if (Serial.find("MOD=")) {
  int ID = Serial.parseInt();
  if (ID == nanoID || ID == 0) {
    Serial.find("CMD=");
    int command = Serial.parseInt();
    int cmdVal = 0;
    if (command != 0){
      Serial.find("VAL=");
      cmdVal = Serial.parseInt();
    }
    Serial.println("MOD: "+String(ID)+", CMD: "+String(command) + ", VAL: " + String(value));
    Serial.print("freeMemory()=");
    Serial.println(freeMemory());
    execOrder(ID,command,cmdVal);
  }
}

And it works flawlessly. But I don't know how to achieve the same results with the RF input. The problem seems to be with using so many strings.

Answer 1

Your problem is not due to memory shortage, but because you are erroneously using pointers.

Even with your fix you are doing the same mistake, you are just not incurring into the same problem by luck as you are not addressing anything new after the bad definition of your variable msgBuff.

Putting all that into simple terms, you should change your code and probably read some articles on C pointers as it looks like you have a Java background (like me).

Your issue is in the char msgBuff[]=""; statement which should be moved after the the call to obtain the payload size and turned into char msgBuff[RFlen];:

int RFlen=radio.getDynamicPayloadSize();
char msgBuff[RFlen];
delay(10);
radio.read(&msgBuff, RFlen);

Answer 2

Ok, I solved it like this:

if (radio.available()){
    int RFlen=0;
    char msgBuff[]="";
    RFlen = radio.getDynamicPayloadSize();
    delay(10);
    radio.read(&msgBuff, RFlen);
    int ID = msgBuff[4] - '0';
    int cmdCode = msgBuff[10] - '0';
    int cmdVal = msgBuff[16] - '0';
    if (cmdCode == 2){
      cmdVal *= 100;
      cmdVal += 10*(msgBuff[17]-'0');
      cmdVal += (msgBuff[18]-'0');
    }
    execOrder(ID,cmdCode,cmdVal);
}

The problem is with using strings, but I don't know why since there's plenty of memory. Anyway, I hope this helps anyone else with the same issue.