I am trying to read data from an Arduino UNO to Raspberry Pi with the python smbus module. The only documentation I could find on the smbus module was here. I am not sure what the cmd means in the module. I can use the write to send data to the Arduino. I have written two simple programs one for read and one for write
The one for write
import smbus
b = smbus.SMBus(0)
while (0==0):
var = input("Value to Write:")
b.write_byte_data(0x10,0x00,int(var))
The one for read
import smbus
bus = smbus.SMBus(0)
var = bus.read_byte_data(0x10,0x00)
print(var)
The Arduino code is
#include <SoftwareSerial.h>
#include <LiquidCrystal.h>
#include <Wire.h>
LiquidCrystal lcd(8,9,4,5,6,7);
int a = 7;
void setup()
{
Serial.begin(9600);
lcd.begin(16,2);
// define slave address (0x2A = 42)
#define SLAVE_ADDRESS 0x10
// initialize i2c as slave
Wire.begin(SLAVE_ADDRESS);
// define callbacks for i2c communication
Wire.onReceive(receiveData);
Wire.onRequest(sendData);
}
void loop(){
}
// callback for received data
void receiveData(int byteCount)
{
Serial.println(byteCount);
for (int i=0;i <= byteCount;i++){
char c = Wire.read();
Serial.println(c);
}
}
// callback for sending data
void sendData()
{
Wire.write(67);
lcd.println("Send Data");
}
When I run the read program it returns "33" every time. The Arduino returns that the the sendData function is called.
I am using a Data Level Shifter and the description says it might be a little sluggish.
Has anyone gotten this to work?
I managed to initiate a communication between an Arduino and a Raspberry Pi. The two are connected using two 5k pullup resistors (see this page). The arduino write a byte on the i2c bus for each request. On the Raspberry Pi, hello
is printed every second.
Arduino code:
#include <Wire.h>
#define SLAVE_ADDRESS 0x2A
void setup() {
// initialize i2c as slave
Wire.begin(SLAVE_ADDRESS);
Wire.onRequest(sendData);
}
void loop() {
}
char data[] = "hello";
int index = 0;
// callback for sending data
void sendData() {
Wire.write(data[index]);
++index;
if (index >= 5) {
index = 0;
}
}
Python code on the Raspberry Pi:
#!/usr/bin/python
import smbus
import time
bus = smbus.SMBus(1)
address = 0x2a
while True:
data = ""
for i in range(0, 5):
data += chr(bus.read_byte(address));
print data
time.sleep(1);
On my Raspberry Pi, the i2c bus is 1. Use the command i2c-detect -y 0
or i2c-detect -y 1
to verify if your Raspberry Pi detect your Arduino.