Roomba 500 Series - Raw encoder counts readings

Question

I have been trying to read Roomba raw encoder counts I am receiving values, but I have a sudden increase/decrease in values as can be seen over here.

142 152

153 166

167 180

181 196

50101 33280

207 223

222 238

236 252

#include <SoftwareSerial.h>
#include <Wire.h>
// Roomba Create2 connection
int rxPin = 10;
int txPin = 11;
SoftwareSerial Roomba(rxPin, txPin);
void setup() {

pinMode(10, INPUT);
  pinMode(11, OUTPUT);
  pinMode(5, OUTPUT);
  Serial.begin(115200);
  Roomba.begin(19200);
  delay(1000);
    Roomba.write(128);  //Start
  Roomba.write(132);  //Full mode
  delay(1000);
}
char command;
void loop() {



  if (Serial.available()){
    command=Serial.read();} 
switch (command)
  {   
    case '8':
  Roomba.write(byte(145));
  Roomba.write(byte(0));
  Roomba.write(byte(0x28));
  Roomba.write(byte(0));
  Roomba.write(byte(0x28));
  delay(50);
  encoder_counts();
  break;
  case '0':
    Roomba.write(byte(145));
  Roomba.write(byte(0));
  Roomba.write(byte(0));
  Roomba.write(byte(0));
  Roomba.write(byte(0));
  break;
  }
}



void encoder_counts()
{
   unsigned int  right_encoder;
    unsigned int   left_encoder;
   byte  bytes[4];   

  Roomba.write(byte(149)); 
  Roomba.write(byte(2));
  Roomba.write(byte(43));
  Roomba.write(byte(44));
  delay(50);
   int i=0;
while(Roomba.available()) { 
  bytes[i++]=Roomba.read();
left_encoder = (unsigned int)(bytes[0] << 8)|(unsigned int)(bytes[1]&0xFF); 
right_encoder =(unsigned  int)(bytes[2] << 8)|(unsigned int)(bytes[3]&0xFF);
}  



Serial.print(right_encoder);
Serial.print("  ");
Serial.println(left_encoder);

}

so please kindly advice, Thank you

Answer 1

Welcome to Robotics, Ahmed. You have posted the code you use to build the encoder counts, but not the code you used to display the counts. I mention this because you have the encoder counts displayed in your post as:

13786.00 13938.00

as in, with a trailing decimal, but your encoder counts are defined in your code to be integers. This could be problematic if the print function is treating your two-byte integer as the first two bytes of a floating point number.

The second issue it looks like you've got is that you're defining your encoder variables as int instead of unsigned int. Per the manual,

encoder [count] is returned as an unsigned 16-bit number, high byte first

Try redefining your right_encoder and left_encoder as unsigned int, and then also try changing the formatting in your print command to something like Serial.print(right_encoder) instead of Serial.print(right_encoder, 2).

If that doesn't work, please edit your question to post the code you're using to display the values.