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3

How can I generate this pulse with an Arduino Micro?

Is it necessary an external component?

enter image description here

share|improve this question
    
how much current will you be drawing / what will it be connected to? – JayEye May 26 at 18:00
    
is only for signal generator experiment – Xetam May 26 at 18:04
1  
Looks like something for a 2-bit DA converter. en.wikipedia.org/wiki/Digital-to-analog_converter. A resistor ladder is the simplest solution; en.wikipedia.org/wiki/Resistor_ladder – Mikael Patel May 26 at 18:22
up vote 7 down vote accepted

Take two 10K or so resistors:

    +5V
     |
    10K
     | 
Pin2-+---> output
     |
    10K
     |
    GND

The following program does the trick:

const uint8_t kPin = 2;
const uint32_t kDelay = 10;  // 100Hz

void setup() {
}

void loop() {
  pinMode(kPin, OUTPUT);
  digitalWrite(kPin, HIGH);
  delay(kDelay);

  pinMode(kPin, INPUT);
  delay(kDelay);

  pinMode(kPin, OUTPUT);
  digitalWrite(kPin, LOW);
  delay(kDelay);

  pinMode(kPin, INPUT);
  delay(kDelay);
}

When Pin2 (or any other pin for that matter) is set as INPUT, it is in high-impedance state (theoretically), so effectively you have a voltage divider giving you 1/2 Vcc. When it is set as OUTPUT, and now assuming that its output impedance is << 10KΩ, it drives the output to either +5V or 0V.

enter image description here

share|improve this answer
    
Obviously, this solution does not generalize to multiple levels; folllow @gerben's solution with a resitor ladder for that. However, I like using tri-state pins in creative ways. Charlieplexing is the canonical such example. – JayEye May 27 at 3:26
up vote 5 down vote

enter image description here

If both inputs are 0V, the output will be 0V.

If both inputs are 5V, the output will be 5V.

If one input is 0V and one 5V the output will be 2.5V.

However, if the device attached to the output doesn't have a high input impedance, the voltage will drop some. You could add an opamp to prevent this.

I think you can generate the 2 pins outputs using one of the timers in phase correct pwm mode. Freeing up the cpu and giving a very clean output signal, as using software "pwm" could be slightly of due to interrupts occuring.

share|improve this answer
    
ha! mine uses only one pin :) What did you use to draw the circuit? – JayEye May 26 at 19:19
    
@JayEye cool solution. Didn't think about tri-state. I used kicad to draw the schematic. – Gerben May 27 at 12:36

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