Raspberry Pi Forums

Code: Select all

Traceback (most recent call last):
  File "/home/pi/sketchbook/I2Ctalk04/I2Ctalk04.py", line 36, in <module>
    readBunchOfData(4)
  File "/home/pi/sketchbook/I2Ctalk04/I2Ctalk04.py", line 25, in readBunchOfData
    myDataHere = readBlockData(numBytes)
  File "/home/pi/sketchbook/I2Ctalk04/I2Ctalk04.py", line 17, in readBlockData
    x = bus.read_i2c_block_data(address, 0, numBytes)
  File "/usr/local/lib/python3.4/dist-packages/smbus2/smbus2.py", line 391, in read_i2c_block_data
    ioctl(self.fd, I2C_SMBUS, msg)
OSError: [Errno 121] Remote I/O error

Code: Select all

from smbus2 import SMBus
import time

bus = SMBus(1)
address = 0x04

def writeNumber(value):
    bus.write_byte(address, value)
    return -1

def readNumber():
    number = bus.read_byte(address)
    return number

def readBlockData(numBytes):
    res3 = []
    x = bus.read_i2c_block_data(address, 0, numBytes)
    res3.extend(x)
    return res3

def readBunchOfData(numBytes):
    # Send number of bytes we are requesting
    writeNumber(numBytes)
    # Receive data
    myDataHere = readBlockData(numBytes)
    # Show what we've got
    print ("We received ", numBytes, " of data")
    for i in range(0, numBytes):
        print (myDataHere[i])
        

while True:
    # For now, hard-code 4 bytes of data
    print ()
    print ("We are requesting ", 4, " bytes of data")
    readBunchOfData(4)
    print ()

Code: Select all

#include <Wire.h>

#define SLAVE_ADDRESS 0x04
int number = 0;
int dataNo = 0;

void setup() {
  Serial.begin(9600);
  Wire.begin(SLAVE_ADDRESS);
  
  Wire.onReceive(receiveData);
  Wire.onRequest(sendData);
  
  Serial.println("Ready!");
}

void loop() {
  doingSomething(10);
}

void doingSomething(int loops) {
  for (int i = 0; i<loops; i++) {
    Serial.print("I'm doing something else...");
    Serial.println(i);
    delay(50);
  }
}

void receiveData(int byteCount) {
  while(Wire.available()) {
    number = Wire.read();
    
    if (dataNo == 0) {
      // dataNo, so this is how many bytes to send - currently hard-coded at 4
      dataNo = number;
    }
    else {
      // We should not get here
      Serial.println("We got to hole 1");
    }  
  }
}

void sendData() {
  byte output[] = {0x01,0x02,0x03,0x04};  // This is just some sample data for testing
  Wire.write(output, 4);
  dataNo = 0;
}