[SOLVED: I didn't have slave code uploaded to the Nano. Still learning. Thanks for the help!]
Beginner here, please forgive me if I'm missing something very simple.
I'm trying to connect a Mega to a Nano using I2C, but the I2C scanner sketch I'm using (below) says "No I2C devices found." So I'm trying to identify where the problem is.
I successfully connected an Uno to the Mega via I2C, so I think the wiring is not at fault. Just in case, though, I'll describe it and post pics.
I have the Mega's 20 pin connected to the Uno's 4 pin and the 21 connected to Uno's 5, each with a 4k7ohm pull-up resistor. The GND and 5V pins are also connected. (pics of wiring below) The I2C scanner sees the Uno. Success!
But when I unplug the wires from the Uno and plug them into the Nano in the same pins, there's no I2C connection.
As far as I can tell, the Nano works fine -- I ran a blink sketch on it, and that worked. Is there some other way I can test to see if/where the problem lies in the Nano?
Am I missing something? Thanks in advance for reading this and apologies if my mistake is very dumb.
Here's the scanner code, if that helps:
// --------------------------------------
// i2c_scanner
//
// Version 1
// This program (or code that looks like it)
// can be found in many places.
// For example on the Arduino.cc forum.
// The original author is not know.
// Version 2, Juni 2012, Using Arduino 1.0.1
// Adapted to be as simple as possible by Arduino.cc user Krodal
// Version 3, Feb 26 2013
// V3 by louarnold
// Version 4, March 3, 2013, Using Arduino 1.0.3
// by Arduino.cc user Krodal.
// Changes by louarnold removed.
// Scanning addresses changed from 0...127 to 1...119,
// according to the i2c scanner by Nick Gammon
// http://www.gammon.com.au/forum/?id=10896
// Version 5, March 28, 2013
// As version 4, but address scans now to 127.
// A sensor seems to use address 120.
// Version 6, November 27, 2015.
// Added waiting for the Leonardo serial communication.
//
//
// This sketch tests the standard 7-bit addresses
// Devices with higher bit address might not be seen properly.
//
#include <Wire.h>
void setup()
{
Wire.begin();
Serial.begin(9600);
Serial.println("\nI2C Scanner");
}
void loop()
{
byte error, address;
int nDevices;
Serial.println("Scanning...");
nDevices = 0;
for(address = 1; address < 127; address++ )
{
// The i2c_scanner uses the return value of
// the Write.endTransmisstion to see if
// a device did acknowledge to the address.
Wire.beginTransmission(address);
error = Wire.endTransmission();
if (error == 0)
{
Serial.print("I2C device found at address 0x");
if (address<16)
Serial.print("0");
Serial.print(address,HEX);
Serial.println(" !");
nDevices++;
}
else if (error==4)
{
Serial.print("Unknown error at address 0x");
if (address<16)
Serial.print("0");
Serial.println(address,HEX);
}
}
if (nDevices == 0)
Serial.println("No I2C devices found\n");
else
Serial.println("done\n");
delay(5000); // wait 5 seconds for next scan
}
