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Connect a 11 positions Rotating Switch to the Arduino using a single input pin

I needed an easy way to select a model among 10 for my Arduino-based RC transmitter.

I used this kind of switch, widely available on Ebay:

10 positions Rotating Switch

Between each contact, I soldered a 1kΩ resistor to make the switch act as a fixed-steps 10kΩ potentiometer.

The cursor of the switch is connected to an analog input of the Arduino, and its position is computed with this simple code:

 // Read the position of the rotary switch
 // return value: [0, ROTARY_SWITCH_STEPS]
 #define ROTARY_SWITCH_PIN A6
 #define ROTARY_SWITCH_STEPS 10
 byte read_rotary_switch() {
	byte retval_byt = 0;
	const unsigned int step_int = 1024 / ROTARY_SWITCH_STEPS;
	const unsigned int offset_int = step_int / 2;
	unsigned int limit_int = offset_int;
	unsigned int sample_int = analogRead(ROTARY_SWITCH_PIN) & 0xFFF8; // filter noise: ignore least significant 3 bits
	while (sample_int > limit_int) {
		retval_byt++;
		limit_int += step_int;
	}
	return retval_byt;
 }

There is no debouncing in this code. If you need it, you'll find a more sophisticated version of this function in the RC transmitter source code.

 
Page last modified on February 03, 2015, at 08:39 AM