Lesson 9 Infrared-Receiver

Introduction

An infrared-receiver is a component that receives infrared signals and can independently receive infrared ray and output signals compatible with TTL level. It’s similar with a normal plastic-packaged transistor in size and it is suitable for all kinds of infrared remote control and infrared transmission.

Components

– 1 * Raspberry Pi

– 1 * Breadboard

– 1 * Network cable (or USB wireless network adapter)

– 1 * Infrared-receiver module

– Several jumper wires

Experimental Principle

Infrared receiving head receives infrared signals.

Experimental Procedures

Step 1: Build the circuit

       Infrared-Receiver Module                           Raspberry Pi

                      S ———————————————- GPIO0

                      + ———————————————- 3.3V

                      – ———————————————– GND

Step 2: Edit and save the code (see path/Rpi_SensorKit_code/29_irRecv/irRecv.c)

Step 3: Compile

              gcc  irRecv.c  -lwiringPi

Step 4: Run

              ./a.out

Here you can see the LED on the module light up when infrared rays are received. At the same time, infrared pulses will be printed on the screen.

irRecv.c 

#include <wiringPi.h>
#include <stdio.h>

#define IR 0

int cnt = 0;

void myISR(void)
{
printf("Recevied infrared. cnt = %d\n", ++cnt); 
}

int main(void)
{
if(wiringPiSetup() == -1){ //when initialize wiring failed,print messageto screen
printf("setup wiringPi failed !");
return 1; 
}

if(wiringPiISR(IR, INT_EDGE_FALLING, &myISR) == -1){
printf("setup ISR failed !");
return 1;
}

//pinMode(IR, INPUT);

while(1);

return 0;
}

Python Code

#!/usr/bin/env python
import RPi.GPIO as GPIO

IrPin  = 11
LedPin = 12

Led_status = 1

def setup():
	GPIO.setmode(GPIO.BOARD)       # Numbers GPIOs by physical location
	GPIO.setup(LedPin, GPIO.OUT)   # Set LedPin's mode is output
	GPIO.setup(IrPin, GPIO.IN, pull_up_down=GPIO.PUD_UP)
	GPIO.output(LedPin, GPIO.LOW) # Set LedPin high(+3.3V) to off led

def swLed(ev=None):
	global Led_status
	Led_status = not Led_status
	GPIO.output(LedPin, Led_status)  # switch led status(on-->off; off-->on)
	if Led_status == 1:
		print 'led on...'
	else:
		print '...led off'

def loop():
	GPIO.add_event_detect(IrPin, GPIO.FALLING, callback=swLed) # wait for falling
	while True:
		pass   # Don't do anything

def destroy():
	GPIO.output(LedPin, GPIO.LOW)     # led off
	GPIO.cleanup()                     # Release resource

if __name__ == '__main__':     # Program start from here
	setup()
	try:
		loop()
	except KeyboardInterrupt:  # When 'Ctrl+C' is pressed, the child program destroy() will be  executed.
		destroy()