atTiny85 5V and servo usage

[CodyMWilson]

Hi all,

I have an atTiny85, and I'd like to control a servo on pin 4. However, this code does not work for me.

`// Trinket Servo Monster sketch
// Hardware: Adafruit Trinket (3V or 5V), micro servo, LED + resistor
// Libraries: uses Adafruit_TiCoServo library to manage servo pulses,
// even though NeoPixels are NOT being used here.

#if !defined(__AVR_ATtiny85__)
 #error "This code is for ATtiny boards"
#endif
#include <Adafruit_TiCoServo.h>
#include <avr/power.h>

// Servo parameters.  Pin MUST be 1 or 4 on a Trinket.  Servo position
// is specified in raw timer/counter ticks (1 tick = 0.128 milliseconds).
// Servo pulse timing is typically 1-2 ms, but can vary slightly among
// servos, so you may need to tweak these limits to match your reality.
#define SERVO_PIN  4 // Pins 1 or 4 are supported on Trinket
#define SERVO_MIN  4 // ~1 ms pulse
#define SERVO_MAX 26 // ~2 ms pulse

#define LED_PIN    0 // "Eye" LED is connected here

Adafruit_TiCoServo servo;

void setup(void) {
#if (F_CPU == 16000000L)
  // 16 MHz Trinket requires setting prescale for correct timing.
  // This MUST be done BEFORE servo.attach()!
  clock_prescale_set(clock_div_1);
#endif
  servo.attach(SERVO_PIN);
  pinMode(LED_PIN, OUTPUT);
  digitalWrite(LED_PIN, HIGH);
}

uint32_t lastLookTime = 0; // Time of last head-turn

void loop(void) {

  unsigned long t = millis(); // Current time

  // If more than 1/2 second has passed since last head turn...
  if((t - lastLookTime) > 500) {
    if(random(10) == 0) { // There's a 1-in-10 chance...
      // ...of randomly moving the head in a new direction:
      servo.write(random(SERVO_MIN, SERVO_MAX));
      lastLookTime = t;   // Save the head-turn time for future reference
    }
  }

  // Unrelated to head-turn check,
  if(random(10) == 0) { // there's a 1-in-10 chance...
    // ...of an "eye blink":
    digitalWrite(LED_PIN, LOW);  // The LED turns OFF
    delay(random(50, 250));      // for just a short random moment
    digitalWrite(LED_PIN, HIGH); // then back ON
  }

  delay(100); // Repeat loop() about 10 times/second
}
`

I'd like to get a servo to run, I've also tried using the TinyServo and PrecisionServo libraries

`#include <TinyServo.h>
const byte SERVOS = 3;
const byte servoPin[SERVOS] = {7};
#define WATERSERVO 4
void setup() {
  // put your setup code here, to run once:
setupServos();
}

void loop() {
  // put your main code here, to run repeatedly:
delay(1000);
moveServo(WATERSERVO, 180);
delay(1000);
moveServo(WATERSERVO, 10);`

Here's the other one

`//
// [email protected]'s ATTiny Hardware Timer Assisted Servo Library v1.0 20-Nov-13
//
// http://code.google.com/p/arduino-tiny/ pinouts
//
//                  ATtiny25/45/85
//                      +-\/-+
//              RESET  1|    |8  VCC
//               3/A3  2|    |7  2/A1
//               4/A2  3|    |6  1
//                GND  4|    |5  0
//                      +----+
//
//                  ATtiny24/44/84
//                      +-\/-+
//                VCC  1|    |14  GND
//                  0  2|    |13  10/A0
//                  1  3|    |12  9/A1
//              RESET  4|    |11  8/A2
//                  2  5|    |10  7/A3
//               3/A7  6|    |9   6/A4
//               4/A6  7|    |8   5/A5
//                      +----+
//
//                    ATtiny2313
//                      +-\/-+
//              RESET  1|    |20  VCC
//                  0  2|    |19  16
//                  1  3|    |18  15
//                  2  4|    |17  14
//                  3  5|    |16  13
//                  4  6|    |15  12
//                  5  7|    |14  11
//                  6  8|    |13  10
//                  7  9|    |12  9
//                GND 10|    |11  8
//                      +----+

#include <TinyServo.h>
const byte SERVOS = 1; // how many servos do you have? up to 5 on ATTiny85 and 8 on ATtiny84/2313
const byte servoPin[SERVOS] = { 4 }; // what pins are your servos on?
// you have the option to give your servos nice names. 0 refers to the first servo pin above, 1 to the second, etc


// ========================================================================================================================
void setup() 
{
  
setupServos();

}

// ========================================================================================================================
void loop() 
{
  
delay(1000);

// servos can be moved individually, by name, to 0° to 180°
moveServo(LEFTLEGSERVO, 180);
moveServo(RIGHTLEGSERVO, 180);
delay(1000);
moveServo(LEFTLEGSERVO, 0);
moveServo(RIGHTLEGSERVO, 0);
delay(1000);

// servos can also be moved en-masse with a loop
for(byte i=0; i <= 180; i++)
  {
  for(byte servo=0; servo < SERVOS; servo++)
    {
    moveServo(servo, i);
    delay(50);
    }
  }

moveServo(LEFTLEGSERVO, 0);
moveServo(RIGHTLEGSERVO, 0);
delay(1000);

// you also have the option of precisely positioning servos by writing directly to the servoPos variables
// to move to 0°, set a value of 0. the value required to move to 180° depends on what chip, timer, and clock speed TinyServo is running on/at:
//       ATtinyx4 / x313 = 225
// ATTinyx5 16MHz Timer1 = 113
// ATTinyx5 16MHz Timer0 = 113
// ATTinyx5 8MHz  Timer1 = 113
// ATTinyx5 8MHz  Timer0 = 57
// The Core defaults to Timer1 on the ATtinyx5, it's recommended you move it to Timer0 by editing /hardware/arduino/cores/tiny/core_build_options.h
servoPos[HEADSERVO] = 50;
delay(1000);

// The maximum value is also available via the SERVOMAX constant
servoPos[HEADSERVO] = 0;
delay(1000);
servoPos[HEADSERVO] = SERVOMAX;

}`

None of these have worked for me. Are there examples of using the Core library for a servo control?

[SpenceKonde]

Is that a fresh tiny85? If so, have you remembered to do "Burn Bootloader" with the desired clock option? A virgin classic AVR always ships with the fuses set for 1 MHz. Since incorrect fuse settings will brick a classic AVR, we follow the convention of every other classic AVR core including the official ones, and only write fuses when doing "burn bootloader". Hence you must do that with a new chip whether or not a bootloader is being used, as well as any time you change one of the settings marked "burn bootloader required" in order for that setting to be applied.

Test with a LED and blink that it is actually running at the clock speed you have selected - if it is blinking faster or (more likely) slower than normal, this is the problem. Since servo control is timing-critical, having the speed set wrong will completely break it.

As for examples of using the included Servo_ATTinyCore... uh, they're kind of included with the core?
https://github.com/SpenceKonde/ATTinyCore/tree/master/avr/libraries/Servo_ATTinyCore/examples

[CodyMWilson]

I have the adafruit trinket 5V atTiny85 - doesn't that already have the clock speed set? Maybe I do need to set the bootloader?