Servo - April 2012

www.servomagazine.com/index.php?/magazine/article/april2012_MrRoboto

an Arduino UNO equivalent board that has 128K Flash and 16K RAM, and the CEREBOT MX3cK with the same specs and Arduino capability, but with the chipKIT pinout instead of Arduino. Also in Figure 1 are the CEREBOT MX4cK (512K Flash/16K RAM) and MX7cK (512K Flash/128K RAM) boards. All are capable of being directly programmed by the Arduino or MPLAB. These boards range in price from under $30 to about $120. Their onboard development capabilities go up with the size and price of the board.

Okay. The boards are capable, look cool in the color red, and have lots of connectors, but how do we use them? The answer involves a bunch of wires. The CEREBOT boards have Pmod cables that nicely interface to Pmod boards (which Digilent has SCORES of!). However, the peculiar connector layout of an Arduino-based footprint does not lend itself well to using the Pmod boards directly. They can be used, but you’ll have to use solderless jumper wires that have a six-pin female connector on one end and a bunch of individual female connectors on the other. Then, route the wires to power, ground, and signal lines as you require.

Like I previously mentioned, I am easily distracted and in the case of your question, got off on a tangent that involved making a six servo hexapod using nine gram servos that I got from Hobby People for $2 each (new!) and just HAD to build! Hobby People continually has outrageous sales on stuff like this; check them out at www.hobby people.net to see what I mean. They are an RC car and airplane distributor, but we hobby robotics folks use a lot of the same electronics and equipment in our playtime.

I am going to use six servos connected to the MAX32 via a PmodCON3 servo Pmod board — actually two of them — to drive my hexapod using an interesting idea that I got from my friend, Dan Michaels and his NICO robot

Figure 2

Listing 1: Some basic Arduino servo code.

// Variation of the Sweep example
// by BARRAGAN <http://barraganstudio.com>
// which is in the public domain.

#include <Servo.h>
Servo leftFront;  // create servo object to control a servo
Servo leftMiddle;
Servo leftRear;
Servo rightFront;
Servo rightMiddle;
Servo rightRear;

int pos = 0; // variable to store the servo position
void setup()
{
  leftFront.attach(8);
  leftMiddle.attach(9);
  leftRear.attach(10);
  rightFront.attach(5);
  rightMiddle.attach(6);
  rightRear.attach(7);
}
void loop()
{
  for(pos = 0; pos < 180; pos += 1)  // goes from 0 to 180 degrees
  { // in steps of 1 degree
 leftFront.write(pos);
 leftMiddle.write(pos);
 leftRear.write(pos);
 rightFront.write(pos);
 rightMiddle.write(pos);
 rightRear.write(pos);
 delay(15);
  }
  for(pos = 180; pos>=1; pos-=1) // goes from 180 to 0 degrees
  {
 leftFront.write(pos);
 leftMiddle.write(pos);
 leftRear.write(pos);
 rightFront.write(pos);
 rightMiddle.write(pos);
 rightRear.write(pos);
 delay(15);
  }
}