sending/parsing serial data from Max->Arduino to control multiple servos

Projects General Guidance
1

Hello,

I am interested in using Max messages to control multiple servo motors, each independently.

I was able to successfully get a system (hardware, programming using the arduino's Servo library) to control multiple motors from the same Max slider value send over serial (usb).

However, I am a relatively inexperienced programmer, and am having trouble coming up with a protocol to parse the serial data in the Arduino code to send one value to one motor, and a second value to another.

I have done a little bit of research and know that the solution probably calls for an index or address character that I would assign to each position value in Max, and that would be parsed and sent to the various motor positions in Arduino. However, I am struggling to figure out how to format this address character (ASCII vs Integer, etc) and how to code in Arduino to read this address and send it to the particular motor it addresses.

Below I've attached an abridged Arduino 2 code of my general motor set up, and a sample Max patch assigning possible address labels.

Any hints/advice/suggestions would be greatly appreciated!

Thanks!
JCR

//concept sketch in Arduino 2 code for controlling 2 independent motors,

#include <Servo.h> //load servo library

Servo servo1; // create servo object to control a servo (part of servo library protocol)
Servo servo2;

unsigned char temp_data = 0; //value for the entire serial read -some combo of address and position values
unsigned char address = 0; //the address value indicating which servo to send position data (1, 2, 3, etc.)
unsigned char pos = 0; //the motor position value, which follows the address (0-179)

unsigned char Max1; // value for servo1 position
unsigned char Max2; // value for servo2 position

//HERE IS WHERE I WOULD DEFINE SOME FUNCTION TO PARSE THE ADDRESS AND POSITION DATA

void setup()
{
servo1.attach(3); // attaches the output on pin 3 to the servo1
servo2.attach(4); // attaches the output on pin 4 to the servo2

Serial.begin(9600);
}

void loop()
{
if (Serial.available()) { //check if data sent from cpu

temp_data = Serial.read(); //assign value for entire serial read

}

if (address = 1) //is for servo1 position -HERE WILL BE THE IF STATEMENT READING THE ADDRESS

{
pos = Max1;
servo1.write(Max1); // sets the servo1 position according to value
}

if (address = 2) //is for servo2 position

{
pos = Max2;
servo2.write(Max2); // sets the servo2 position according to value
}

delay(15); // waits for the servo to get there
}


----------begin_max5_patcher----------
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-----------end_max5_patcher-----------
2

You might try something like below.

//zoomkat 11-22-12 simple delimited ',' string parse 
//from serial port input (via serial monitor)
//and print result out serial port
//multi servos added 

String readString;
#include <Servo.h> 
Servo myservoa, myservob, myservoc, myservod;  // create servo object to control a servo 

void setup() {
  Serial.begin(9600);

  //myservoa.writeMicroseconds(1500); //set initial servo position if desired

  myservoa.attach(6);  //the pin for the servoa control
  myservob.attach(7);  //the pin for the servob control
  myservoc.attach(8);  //the pin for the servoc control
  myservod.attach(9);  //the pin for the servod control 
  Serial.println("multi-servo-delimit-test-dual-input-11-22-12"); // so I can keep track of what is loaded
}

void loop() {

  //expect single strings like 700a, or 1500c, or 2000d,
  //or like 30c, or 90a, or 180d,
  //or combined like 30c,180b,70a,120d,

  if (Serial.available())  {
    char c = Serial.read();  //gets one byte from serial buffer
    if (c == ',') {
      if (readString.length() >1) {
        Serial.println(readString); //prints string to serial port out

        int n = readString.toInt();  //convert readString into a number

        // auto select appropriate value, copied from someone elses code.
        if(n >= 500)
        {
          Serial.print("writing Microseconds: ");
          Serial.println(n);
          if(readString.indexOf('a') >0) myservoa.writeMicroseconds(n);
          if(readString.indexOf('b') >0) myservob.writeMicroseconds(n);
          if(readString.indexOf('c') >0) myservoc.writeMicroseconds(n);
          if(readString.indexOf('d') >0) myservod.writeMicroseconds(n);
        }
        else
        {   
          Serial.print("writing Angle: ");
          Serial.println(n);
          if(readString.indexOf('a') >0) myservoa.write(n);
          if(readString.indexOf('b') >0) myservob.write(n);
          if(readString.indexOf('c') >0) myservoc.write(n);
          if(readString.indexOf('d') >0) myservod.write(n);
        }
         readString=""; //clears variable for new input
      }
    }  
    else {     
      readString += c; //makes the string readString
    }
  }
}
3

Thanks Zoomcat,

I used the little Max patch below to send data to the serial object formatted as: position value, servo designator letter, and a comma (101a,102a,103a,56b,57b,200c,199c, etc).

The serial reader of your Arduino code read the values and sliced the designator and comma off to give me data like:
"92c
writing Angle: 92
95c
writing Angle: 95
100c
writing Angle: 100
112c
writing Angle: 112
116c
writing Angle: 116
120c
..."

However, I'm still not sure how to parse this data to send to various Servo.writes. This may even be included in the Arduino code you sent, but I'm not experienced with this language and am having a hard time conceptualizing how to separate these data based on the letter designation and comma in between them (which I'm not married to, if there is an easier way to format the data to be isolated in a string).

Any further hints/suggestions would be greatly appreciated. Thanks!


----------begin_max5_patcher----------
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-----------end_max5_patcher-----------
4

Good day,

I have tried your approached and found it complexe, I am also not an expert but found a different approach in API mode. Also take in consideration that I am using xbees series 1 but the logic I am applying could be applied to any sketch. I am simply passing analog values across and the sketch could b modified easily.

I am still building this sketch, at the present moment I am only passing 1 analog value from the pot, I am trying to include another signal to the sketch ending up passing analog X&Y and controlling 2 motors independently.

The trick is to parse the information received

http://forum.arduino.cc/index.php?topic=181305.0

Fabiolus

5

Thanks for all the replies so far, but unfortunately I'm still at a loss as to how to define a system of flags/tags in the Arduino code to separate the value following the tag coming in from the Serial.read (the number preceding the letter designation a, b, c, in my previous example...though it would probably make more sense to have the letter tag come first: a128, rather than 128a, ).

So it would isolate "A138," as the value 138, and I could then define a variable for all values coming in with that have the "A" tag, and set "servo A" to read to those only those values, the "servo B" to read only values with a "B" tag, etc.

Thanks again for all your help!
J

6

Using the code I posted, when you send the control strings using the serial monitor, your servos do not respond? Perhaps your "Max patch" is causing issues.