Arduino Uno SoftwareSerial and Serial conflict

Question

I have a very simple setup with an Arduino Uno R3 connected to my Windows 7 x64 with Arduino 1.0.1.

I have a RF receiver connected to the Arduino on the DI10 port using the SoftwareSerial library. I am using a AM-RRQ3-433 module. See rfsolutions.co.uk/acatalog/AM_Super-heterodyne_Receiver.html

When I receive a byte from the RF receiver, I am simply writing it to the Serial (so that I can see it on my PC in the serial monitor). Doing so seems to conflict between SoftwareSerial and Serial, since the available() function rapidly increases and thus I have a lot of 0's printed (given no data was actually transmitted, but available() returned 63 - the maximum of the receive buffer).

The Arduino code is as follows:

#include <SoftwareSerial.h>
#define rxPin 10
#define txPin 11

SoftwareSerial rf(rxPin, txPin);
int incomingByte = 0;

void setup() {
  pinMode(rxPin, INPUT);  
  Serial.begin(57600);
  rf.begin(2400);
}

void loop() {
  if (rf.available() > 0) {
    incomingByte = rf.read();
    Serial.println(incomingByte, DEC);
  }
}

As a side note, if I remove the pinMode(rxPin, INPUT) line then nothing is ever received (and rf.available() is always 0).

Answer 1

I do not thing that using SoftwareSerial and Serial at the same time is a problem. I am using SoftwareSerial to communicate with my GSM module and use Serial.print(ln) at the same time for debugging.

However to test this is easy: comment out the Serial.println and set the oboard LED on the Uno when available() returns 63 and off when != 63.

If you still notice the input buffer fills up, reading the RF module is the problem.

BTW what kind of RF module are you using?

Answer 2

First, you may need to use Serial.print() instead of Serial.println(). Also, one thing to keep in mind is that the SoftwareSerial.h library was changed last year and it requires a different format when you're using Serial.print(). You may actually need to change your output line to

 Serial.print( (Dec) incomingByte );

I had to do this for one of my projects.