2

Board: "ATtiny25/45/85"

Processor: "ATtiny85"

Clock: "Internal 1 MHz"

Programmer: "Arduino as ISP"

I want to run a servo forwards and backwards on an ATtiny85. The servo library is not compatible with the ATtiny85 so I had to write code from scratch. At this point, the code that makes the servo go forwards (clockwise) is:

void setup() {
  pinMode(PB1, OUTPUT);
}

void loop() {
  digitalWrite(PB1, HIGH);
  delayMicroseconds(1000);
  // 1 millisecond determines the servo going forwards
  digitalWrite(PB1, LOW);
  delay(19);
}

And the code that makes the servo go backwards (anti-clockwise) is simply by changing the amount of microseconds to:

delayMicroseconds(2000);

I want to have the servo motor go forwards one cycle for a few seconds and then go backwards for a few. I want this to keep looping. At this point my code is:

void setup() {
  pinMode(PB1, OUTPUT);
}

void loop() {
  digitalWrite(PB1, HIGH);
  delayMicroseconds(1000);
  digitalWrite(PB1, LOW);
  delay(19);
  digitalWrite(PB1, HIGH);
  delayMicroseconds(2000);
  digitalWrite(PB1, LOW);
  delay(19);
}

This however just makes the servo go back and forward at the same spot forever. I do realise I might need a for loop for this but I am confused as how I will do this.

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3
  • Did you have a try on using 8MHz. Commented Sep 15, 2017 at 2:16
  • @AllenChak yeah I did try that however, that still doesn't produce the output that i want because I want the servo to spin forwards and backwards in a row rather than separately. Commented Sep 15, 2017 at 4:05
  • 1
    Try this link: forum.arduino.cc/index.php?topic=62912.msg459183#msg459183 Commented Sep 15, 2017 at 7:08

1 Answer 1

Reset to default
2

The servo can't move back and forward in 40 milliseconds. It'll be more like tremble between both.

Try something like this:

// keep sending 0 position for about 400ms
for(int i = 0; i<20; ++i) {
  digitalWrite(PB1, HIGH);
  delayMicroseconds(1000);
  digitalWrite(PB1, LOW);
  delay(19);
}

// keep sending second position for about 400ms
for(int i = 0; i<20; ++i) {
  digitalWrite(PB1, HIGH);
  delayMicroseconds(2000);
  digitalWrite(PB1, LOW);
  delay(18);
}
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3
  • Hi thanks a lot it really helped and it makes sense too. I just have one question, that delay(19) when changed to delay(20) the servo behaves differently. Why is that delay kept at 19 milliseconds and not something else? thanks again. Commented Sep 15, 2017 at 14:35
  • 1
    The servo expects pulses at 20ms rate (= 50Hz) including High side pulse width. Commented Sep 15, 2017 at 14:54
  • In trying to find basic code to work a servo, this helped a lot. Thank you! Commented Apr 21, 2021 at 9:28

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