updated servodemo

Author: ladyada

examples/servo/servo.ino

@@ -33,9 +33,9 @@ Adafruit_PWMServoDriver pwm = Adafruit_PWMServoDriver();
 // have!
 #define SERVOMIN  150 // This is the 'minimum' pulse length count (out of 4096)
 #define SERVOMAX  600 // This is the 'maximum' pulse length count (out of 4096)
-#define USMIN  611 // This is the rounded 'minimum' microsecond length based on the minimum pulse of 150
-#define USMAX  2441 // This is the rounded 'maximum' microsecond length based on the maximum pulse of 600
-#define FREQ 60 // Analog servos run at ~60 Hz updates
+#define USMIN  600 // This is the rounded 'minimum' microsecond length based on the minimum pulse of 150
+#define USMAX  2400 // This is the rounded 'maximum' microsecond length based on the maximum pulse of 600
+#define SERVO_FREQ 60 // Analog servos run at ~60 Hz updates
 
 // our servo # counter
 uint8_t servonum = 0;
@@ -45,8 +45,11 @@ void setup() {
   Serial.println("8 channel Servo test!");
 
   pwm.begin();
-  
-  pwm.setPWMFreq(FREQ);  // Analog servos run at ~60 Hz updates
+  // In theory the internal oscillator is 25MHz but it really isn't
+  // that precise. You can 'calibrate' by tweaking this number till
+  // you get the frequency you're expecting!
+  pwm.setOscillatorFrequency(27000000);  // The int.osc. is closer to 27MHz  
+  pwm.setPWMFreq(SERVO_FREQ);  // Analog servos run at ~60 Hz updates
 
   delay(10);
 }
@@ -57,7 +60,7 @@ void setServoPulse(uint8_t n, double pulse) {
   double pulselength;
 
   pulselength = 1000000;   // 1,000,000 us per second
-  pulselength /= FREQ;   // Analog servos run at ~60 Hz updates
+  pulselength /= SERVO_FREQ;   // Analog servos run at ~60 Hz updates
   Serial.print(pulselength); Serial.println(" us per period"); 
   pulselength /= 4096;  // 12 bits of resolution
   Serial.print(pulselength); Serial.println(" us per bit"); 
@@ -94,6 +97,6 @@ void loop() {
 
   delay(500);
 
-  servonum ++;
+  servonum++;
   if (servonum > 7) servonum = 0; // Testing the first 8 servo channels
-}
+}