call of overloaded write(int) is ambiguous

Question

The code below works fine WITHOUT the function spinLeft() (which I copied from goForward and modified). When I tried to add that function (to be used later) I got the error above. But I can't see where I did anything not already done. How did adding another function generate this error?

The rest of the error message says:

Roomba4operants.ino: In function 'void spinLeft()':
Roomba4operants:57: error: call of overloaded 'write(int)' is ambiguous
/Users/royclymer/Desktop/Arduino.app/Contents/Resources/Java/libraries/SoftwareSerial/SoftwareSerial.h:92: note: candidates are: virtual size_t SoftwareSerial::write(uint8_t)
/Users/royclymer/Desktop/Arduino.app/Contents/Resources/Java/hardware/arduino/cores/arduino/Print.h:49: note:                 size_t Print::write(const char*)

Code:

#include <SoftwareSerial.h>

int rxPin = 3;
int txPin = 6;
int ledPin = 13;

SoftwareSerial Roomba(rxPin,txPin);

void setup() {
  pinMode(ledPin, OUTPUT);   // sets the pins as output
  Serial.begin(115200);
  Roomba.begin(115200);  
  digitalWrite(ledPin, HIGH); // say we're alive
  Serial.println ("Sending start command...");
  delay (1000);
   // set up ROI to receive commands  
  Roomba.write(128);  // START
  delay(150);
  Serial.println ("Sending Safe Mode command...");
  delay (1000);
  Roomba.write(131);  // SAFE
  delay(150);
  digitalWrite(ledPin, LOW);  // say we've finished setup
  Serial.println ("Ready to go!");
  delay (5000);
}

void loop() {
  digitalWrite(ledPin, HIGH); // say we're starting loop
  Serial.println ("Go Forward");
  goForward();
  delay (1000);
  Serial.println ("Halt!");
  halt();
  Serial.println ("Go Backwards");
  delay (200);
  goBackward();
  delay (1000);
  Serial.println ("Halt!");
  halt();
  while(1) { } // Stop program
}

void goForward() {
  Roomba.write(137);   // DRIVE
  Roomba.write((byte)0x00);   // 0x00c8 == 200
  Roomba.write(0xc8);
  Roomba.write(0x80);
  Roomba.write((byte)0x00);
}

void spinLeft() {
  Roomba.write(137);   // DRIVE
  Roomba.write((byte)0x00);   // 0x00c8 == 200
  Roomba.write(0xc8);
  Roomba.write(0x00);         //0x0001==spin left
  Roomba.write((byte)0x01);
}

void goBackward() {
  Roomba.write(137);   // DRIVE
  Roomba.write(0xff);   // 0xff38 == -200
  Roomba.write(0x38);
  Roomba.write(0x80);
  Roomba.write((byte)0x00);
}

void halt(){
 byte j = 0x00;
 Roomba.write(137);   
 Roomba.write(j);   
 Roomba.write(j);
 Roomba.write(j);
 Roomba.write(j);
}

Answer 1

0x00 can be interpreted as both an integer literal or a pointer literal. The compiler doesn't know which you mean, as you have overloads for both.

So change that line to:

Roomba.write((byte)0x00);

or the slightly more verbose C++-style cast:

Roomba.write(static_cast<byte>(0x00));