For the second part of the robotic arm project my task was to write a piece of software that controls the arm and allows debugging it, as well as learning about it's behaviour for the development of more sophisticated software. The group documentation can be found here.
The other half of my contribution can be found at the Mechanical Design exercise.
To get support of the 1284p that is used on the board controlling the robotic arm I downloaded a forked version of Mighty 1284p and unzipped it to .../Arduino/hardware. Now I restarted the ArduinoIDE and could select "maniacbug Mighty 1284p using Optiboot" from the boards menu.
The software is controlled over the serial monitor and can be used to learn about the way the robotic arm makes it's movements. Later the target values could be pre-defined or even calculated on the go. The only thing really needed is a reliable zero position, otherwise movements can not be reused. Complex tasks could be fulfilled by chaining multiple calls to moveTo. A problem with this code is that it's still moving step by step and has no concept of acceleration and deceleration.
roboticArm.ino#include <Stepper.h>
Stepper motors[] = {
// The first value is the number of steps the motor needs for one revolution, adjust it accordingly
Stepper (200, PA0, PA1, PA2, PA3), // Base
Stepper (200, PB0, PB1, PB2, PB3), // Joint one, just double the wires to send the signal to both motors
Stepper (200, PC0, PC1, PC2, PC3) // Joint two
};
// This can be any position of the arm but the movements will be relative to it
int steps[] = {0, 0, 0};
// fin[] and finCount have to be reset before a new target
boolean fin[] = {false, false, false};
int finCount = 0;
// These are used to hold the serial input
int a = 0; int b = 0; int c = 0;
void setup()
{
Serial.begin(9600);
}
void loop() {
Serial.flush();
Serial.write("Enter target position");
Serial.write("Base");
while(!Serial.available());
a = Serial.read();
Serial.flush();
Serial.write("Joint 1");
while(!Serial.available());
b = Serial.read();
Serial.flush();
Serial.write("Joint 2");
while(!Serial.available());
c = Serial.read();
Serial.flush();
moveTo(a,b,c);
}
void moveTo(int baseTarget, int jointOneTarget, int jointTwoTarget){
while(finCount < 3){ // When all three have finished we are done
//Move each motor one step towards the target positiont
moveMotorOneStep(0, baseTarget);
moveMotorOneStep(1, jointOneTarget);
moveMotorOneStep(2, jointTwoTarget);
}
}
void moveMotorOneStep(int motor, int target){
if(steps[motor] < target){ // We need to move forward
motors[motor].step(1);
steps[motor]++;
}
else if(steps[motor] > target){ // We need to move back
motors[motor].step(-1);
steps[motor]--;
}else if(fin[motor] == false) { // we are in the target position
fin[motor] = true;
finCount++;
}
}