PIC18F I2C Communication with Arduino

[HenrikOlsson]

The data being sent is the value 0, that looks alright to me though I've literally never used I2CWrite.
Check the pins you're using for multiplexed functions, specifically analog such as ADC and comparators and make sure the pins are set to digital.

Then I'd check the pins with a scope or logic analyzer to verify if data is actually coming out or not - if you don't KNOW, for sure, that the Arduino code is working.

/Henrik.

[Dave]

I've literally never used I2CWrite.
Really Henrick? Wow, I use it all the time to write to serial eeprom's, a/d's and i/o expanders, etc. You should really design more hardware..

[Scampy]

Can you inform us which 18F pic you are using?

Most of the 18F PICs (28 pin and 40 pin) have the hardware I2C pins on PORT C not PORTB. Whilst I'm sure PBP can define any pins, it might be "better" to use the actual pins associated with the hardware module on the PIC, eg

SCLpin             var PORTC.3          'clk
SDApin             var PORTC.4          'data

[picmilan]

I am using PIC18F2450 which doesn't have hardware I2C pins.Isn't I2CWRITE just a software solution and not using actual hardware?

here is arduino code:

#include <Wire.h>

void setup() {
  Wire.begin(0x26);                // join i2c bus with address
  Wire.onReceive(receiveEvent); 
  Serial.begin(9600);          
  
}

void loop() {
 delay(1000);

}


void receiveEvent(int howMany) {

  while (1 < Wire.available()) { 
    char c = Wire.read(); 
    Serial.print(c);    
  }
  int x = Wire.read();   
  Serial.println(x);
}

[picmilan]

I am using 2 2.2K pull up resistors on pins.

Correct arduino code:

#include <Wire.h>

void setup() {
  Wire.begin(0x26);                // join i2c bus with address
  Wire.onReceive(receiveEvent); 
  Serial.begin(9600);          
  
}

void loop() {
 delay(1000);

}
void receiveEvent(int howMany) {

while(Wire.available() > 0){  
  int x = Wire.read();    
 Serial.println(x); 
  }
}

[HenrikOlsson]

Dave,
I do design hardware from time to time but yeah, I'd love to do more. I tend to use SPI as I think it's both easier and faster and all the functions you mention are available in chips with SPI-interface as well as I2C so I've never actually had the need TO use it - that's it really.

Scampy,
I2C/Read/Write are not "hardware assisted" commands, they do not use the (M)SSP module in the PIC so any pins can be used.

picmilan,
I'll repeat what I said earlier: Check if the pins you're using has analog functions and make sure they're turned off.

/Henrik.

[picmilan]

picmilan,
I'll repeat what I said earlier: Check if the pins you're using has analog functions and make sure they're turned off.

/Henrik.

Yeah,You are right! Looking at datasheet those pins are analog by default..

Now Control Address and write address is what confuses me.Control Address is 0x26 as defined in arduino code,right? so what is write address?

Is SPI easier? I don't have many pins available but if I2C doesn't work I guess I don't have any other option.