Generate particular pulse using Arduino

Question

How can I generate this pulse with an Arduino Micro?

Is it necessary an external component?

enter image description here

• JayEye: how much current will you be drawing / what will it be connected to?
• Xetam: is only for signal generator experiment
• Mikael Patel: 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

Answer 1

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

• JayEye: 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.

Answer 2

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.

• JayEye: ha! mine uses only one pin :) What did you use to draw the circuit?
• Gerben: @JayEye cool solution. Didn't think about tri-state. I used kicad to draw the schematic.