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Raspberry Pi to Arduino communication using I2C and interrupts.
/*
* RPi2c - test i2c communication between an Arduino and a Raspberry Pi.
*
* Copyright (c) 2013 Carlos Rodrigues <cefrodrigues@gmail.com>
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include <Wire.h>
static const char intPin = 8;
static const char ledPin = 9;
static const char sensorPin = A0;
short ledValue = 0;
short sensorCurr = 0;
short sensorPrev = -10;
void setup()
{
pinMode(intPin, OUTPUT);
pinMode(ledPin, OUTPUT);
Wire.begin(0x03);
Wire.onReceive(receiveEvent);
Wire.onRequest(requestEvent);
}
void loop() {
sensorCurr = 0;
// Take a few samples and average the results to avoid jitter...
for (int i = 0; i < 10; i++) {
sensorCurr += analogRead(sensorPin);
delay(1);
}
sensorCurr /= 10;
// Trigger an interrupt on the RPi when the sensor changes...
if (abs(sensorCurr - sensorPrev) > 1) {
sensorPrev = sensorCurr;
digitalWrite(intPin, HIGH);
delay(10);
digitalWrite(intPin, LOW);
}
}
void receiveEvent(int bytes) {
int operation = Wire.read();
// Change the LED intensity...
if (operation == 0x01 && bytes > 1) {
ledValue = Wire.read();
analogWrite(ledPin, ledValue);
}
// Consume any remainder bytes...
while (Wire.available()) {
Wire.read();
}
}
void requestEvent() {
// Both the Arduino and RPi are little-endian, no conversion needed...
Wire.write((uint8_t *)&sensorCurr, sizeof(sensorCurr));
}
/* EOF - RPi2c.pde */
#!/usr/bin/env python
#
# RPi2c - test i2c communication between an Arduino and a Raspberry Pi.
#
# Copyright (c) 2013 Carlos Rodrigues <cefrodrigues@gmail.com>
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
#
from __future__ import division
from __future__ import print_function
import RPi.GPIO as GPIO
import smbus
import time
import sys
I2C_BUS = 1
I2C_SLAVE = 0x03
INTERRUPT_PIN = 17
def interpolate(value, a1, a2, b1, b2):
# Normalize the value into a 0..1 interval...
n = float(value - a1) / float(a2 - a1)
# Scale the normalized value to the target interval...
return b1 + (n * (b2 - b1))
if __name__ == '__main__':
# Initialize the interrupt pin...
GPIO.setmode(GPIO.BCM)
GPIO.setup(INTERRUPT_PIN, GPIO.IN)
# Initialize the RPi I2C bus...
i2c = smbus.SMBus(I2C_BUS)
while 1:
try:
# Wait until the Arduino triggers the interrupt...
GPIO.wait_for_edge(INTERRUPT_PIN, GPIO.RISING)
try:
# Get the sensor value from the Arduino (signed 16bit little-endian)...
sensor_value = i2c.read_word_data(I2C_SLAVE, 0x00)
sys.stdout.write("sensor: %d" % sensor_value)
except IOError:
sys.stderr.write("*** error: receiving sensor value ***\n")
continue
sys.stdout.write(" / ")
try:
# Map the sensor value to a [0, 255] interval...
led_value = int(interpolate(sensor_value, 0, 1023, 0, 255))
sys.stdout.write("led: %d\n" % led_value)
# Send the PWM value for the LED to the Arduino...
i2c.write_byte_data(I2C_SLAVE, 0x01, led_value)
except IOError:
sys.stderr.write("*** error: sending led value ***\n")
except KeyboardInterrupt:
GPIO.cleanup()
# vim: set expandtab ts=4 sw=4:
@OlavGullaksen

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OlavGullaksen commented Feb 26, 2016

Hi carlosefr,
I have downloaded your code and it works perfectly and is a very good example indeed of connecting RPi and arduino with the I2C bus.
Br, Olav

@Jonathan-Rosewood

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Jonathan-Rosewood commented Apr 29, 2017

What about any protocol? :)

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