Arduino with structures invalid output

Question

Am trying to write Arduino code to control few stepper motors from my c++ app through serial communication. the code i wrote seems to be ok but it gives strange type of output when i send serial command from my c++ app or Arduino IDE serial monitor.

code

    #include <AccelStepper.h>
    // BaudRate
    #define BAUD 9600

    #define NO_OF_STEPPERS 3  // total # of stepper motors  + 1 , as our motor count star from 1 not from 0 , 

    struct steppers_struct {
      int stepper_id = 0;  // stepper no
      bool status = false;  // status bool 
      int steps_2_move = 0;  // steps the motor needs to move.

    };
    steppers_struct  steppers_rack[NO_OF_STEPPERS]; // init structure

    // Step and Dir pins Array 
    int step_pin_m[NO_OF_STEPPERS];
    int dir_pin_m[NO_OF_STEPPERS];
    int enable_pin_m[NO_OF_STEPPERS];

    // AcceStepper Stepper Array
    AccelStepper stepper_m[NO_OF_STEPPERS];

    // Driver A4988
    #define motorInterfaceType 1

    // Buffer
    char buf[80];

    // Readline funtion load buffer
    int readline(int readch, char *buffer, int len) {
        static int pos = 0;
        int rpos;

        if (readch > 0) {
            switch (readch) {
                case '\r': // Ignore CR
                    break;
                case '\n': // Return on new-line
                    rpos = pos;
                    pos = 0;  // Reset position index ready for next time
                    return rpos;
                default:
                    if (pos < len-1) {
                        buffer[pos++] = readch;
                        buffer[pos] = 0;
                    }
            }
        }
        return 0;
    }

    // Setup 
    void setup() {
        Serial.begin(BAUD);  // init serial

      // stepper dir and step pins. 
      step_pin_m[1] = 2;
      dir_pin_m[1] = 5;
      enable_pin_m[1] = 8; // on CNC shield v3 its pin 8

      step_pin_m[2] = 3;
      dir_pin_m[2] = 6;
      enable_pin_m[2] = 8; // on CNC shield v3 its pin 8


      for(int i=1; i<=NO_OF_STEPPERS; i++)
      {
          stepper_m[i] = AccelStepper(motorInterfaceType, step_pin_m[i], dir_pin_m[i]);   
          stepper_m[i].setMaxSpeed(1000);
          stepper_m[i].setSpeed(1000);  
          pinMode(enable_pin_m[i], OUTPUT);   // Enable Motors
          Serial.print("AccelStepper initalized..");Serial.print("\n");     
      }

      // Some LED
     // pinMode(53, OUTPUT); // Red LED it D53
     // pinMode(52, OUTPUT); // Green LED it D52  
    }


    void loop() {
       // Serial Read Start
       if (readline(Serial.read(), buf, 80) > 0) {
      // command format 1:100;2:200;3:300
      // Read each command pair 

        char* command = strtok(buf, ";");
          while (command != 0)
          {
        // Split the command in two values
        char* separator = strchr(command, ':');
        if (separator != 0)
        {
            // Actually split the string in 2: replace ':' with 0
            *separator = 0;
            int stepperId = atoi(command);
            ++separator;
            int stepperSteps = atoi(separator);

            // Steppers id stars from 1
            if(stepperId != 0){   

            steppers_rack[stepperId].stepper_id = stepperId;
            steppers_rack[stepperId].steps_2_move = stepperSteps;
            if(stepperSteps != 0){
                steppers_rack[stepperId].status = true;
            }else{
                steppers_rack[stepperId].status = false;
            }
               //   Serial.print(" stepper id: "); Serial.print(steppers_rack[stepperId].stepper_id); Serial.print(" stepper steps: "); Serial.print(steppers_rack[stepperId].steps_2_move); Serial.print("\n");    // output OK.
            }   

        } // if end
        // Find the next command in input string
        command = strtok(0, ";");

        }  // while end   
       } // Serial Read End

    // Problems start here when i try to use or change stepper structure data. 

     // Loop on Stepper_Struct
      for(int i=1; i<=NO_OF_STEPPERS; i++)
      {   
        if(steppers_rack[i].steps_2_move != 0 && steppers_rack[i].status == true){
   Serial.print(" stepper id : ");  Serial.print(steppers_rack[i].stepper_id); Serial.print(" Steps to move : ");  Serial.print(steppers_rack[i].steps_2_move);  Serial.print(" status : ");   Serial.print(steppers_rack[i].status);  Serial.print("\n");  // Output not OK
    delay(500);   
              // Lets move stepper motor one step it time so that all motors looks moving it same time , sync
              stepper_m[i].move(1); // this states to move one step ahead
              stepper_m[i].runToPosition();
              steppers_rack[i].steps_2_move -- ;  // deducted one step from the total step motors is told to take
            if(steppers_rack[i].steps_2_move == 0){
              steppers_rack[i].status = false;
            }
        }  // if end
      }  // for end
    } // loop end

so here are few known issues am experiencing with it

1) first when i send command (1:3;2:3) from Arduino Serial Monitor then it not display any output , i have to send it two times then i see output in serial Monitor.

2) another main issue is strange output i get when i sent command : 1:3;2:3 ( mean stepper 1 move 3 steps and stepper 2 also move 3 steps )

 stepper id : 14897 Steps to move : 14848 status : 51
 stepper id : 14897 Steps to move : 59 status : 51
 stepper id : 14897 Steps to move : 12858 status : 51
 stepper id : 14897 Steps to move : 12857 status : 51
 stepper id : 14897 Steps to move : 12856 status : 51
 stepper id : 1 Steps to move : 372 status : 1
 stepper id : 49 Steps to move : 12855 status : 51
 stepper id : 1 Steps to move : 371 status : 1
 stepper id : 49 Steps to move : 12854 status : 51

so am not sure from where these big numbers 14897 , 51 , 49 etc are coming ?

so any idea what am doing wrong and to make the code working so that i can sync multiple stepper motors.

sorry i had to add all code in case someone try to run and debug it

51 is ASCII code of character '3', 49 is '1'. you can strtok with more separators like ",:" — Juraj
– Juraj, Commented Jul 12, 2019 at 12:44
some example of strtok stackoverflow.com/questions/56939302/… — Juraj
– Juraj, Commented Jul 12, 2019 at 12:48
@Juraj am already splitting it by : the output get messy in Loop on Stepper_Struct ... above it you can see i have write output OK — user889030
– user889030, Commented Jul 12, 2019 at 13:22

Kentaro Okuda · Accepted Answer · 2019-07-12 18:18:31Z

1

I see an array index out of bounds problem.

You declared an array of struct this way.

#define NO_OF_STEPPERS 2  // total # of stepper motors
steppers_struct  steppers_rack[NO_OF_STEPPERS]; // init structure

The number of elements in steppers_rack is 2.

Now, you are accessing steppers_rack[2] in the for loop below. Index 2 is out of the bounds.

for(int i=1; i<=NO_OF_STEPPERS; i++) {
  if (steppers_rack[i].steps_2_move != 0 && steppers_rack[i].status == true) {

When i is 2, steppers_rack[i].steps_2_move and steppers_rack[i].status return something other than 0 and the if statement evaluates to true.

answered Jul 12, 2019 at 18:18

Kentaro Okuda

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2 Comments

user889030 Over a year ago

yes good point i updated the code [ #define NO_OF_STEPPERS 3 // total motors + 1 ] and test it and its producing same problem :(

Kentaro Okuda Over a year ago

Try changing for(int i=1; i<=NO_OF_STEPPERS; i++) to for(int i=1; i < NO_OF_STEPPERS; i++).

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