13. Networking and Communications

design and build a wired &/or wireless network connecting at least two processors

I2C Communication

For my final project, I need to make get signal from mpu6050 3-axis accelerometer. But I had no idea to how I2C works, I decided to try with Hello I2C board. I added names on the boards. And I read the wire library reference page on arduino.cc. It was hard to use the wire library because of ATtiny has only few memory for the wire library.

I found a useful website in here. The ATtiny85 (and it's cousins) does not have I2C (or SPI) "built in". Instead it has a Universal Serial Interface (USI) that can be used to facilitate I2C and SPI.

I used Tinywire library, Arduino IDE, SoftwareSerial, but It doesn’t work. I didn’t figure out yet what is the problem.

Download - TinyWire Master library
Download - TinyWire Slave library

Arduino Sketch

I wanted to make simple code that master just pass the data to the slaves which I send it from computer using SoftwareSerial
Master Code on the bridge board

#include <TinyWireM.h>
#include <USI_TWI_Master.h>
#include <SoftwareSerial.h>

SoftwareSerial TinySerial(3, 4);
#define Device1_address 0x26

int received;

void setup(){
TinyWireM.begin();
TinySerial.begin(9600);
TinySerial.println("Tiny Serial Connected");
}

void loop() {
if(TinySerial.available()) {
   received = TinySerial.read();
   TinySerial.println(" Starting Transmission");
   TinySerial.println(received);
   TinyWireM.beginTransmission(Device1_address);
   TinyWireM.send(received);
   TinyWireM.endTransmission();
   TinySerial.println("ended");
}
}

Slave Code on the node board

#include "TinyWireS.h"
#define I2C_SLAVE_ADDR 0x26

void setup() {
pinMode(4, OUTPUT);
TinyWireS.begin(I2C_SLAVE_ADDR);
}

void loop() {
byte byteRcvd = 0;
if (TinyWireS.available()){
   byteRcvd = TinyWireS.receive();
   if(byteRcvd ==0x01){
     digitalWrite(4, HIGH);
   }}}

Failure

Serial Communication works, but the wrong value came out from ATtiny45. I thought that It was problem about 1MHz/8MHz. or because of the ATTiny, there are only mentioned about ATtiny85 on github. I search for the difference with ATtiny45 and ATtiny85, but there are nothing big difference except EEPROM memory. I changed to 1MHz, but It couldn't be uploaded because SoftwareSerial couldn't work on 1MHz. So I tried with no Serial communication and just send specific data to slave on 1MHz. Then It works.

MPU6050 using I2C

I designed for a tiny MPU 6050 sensor and tried to program it using I2C arduino library.

download the eagle files

Failure

MPU6050 package is too small to cut by 1/64 mill, so I tried to cut by hand using box cutter. but I trusted myself moo much. as you can see the picture, It was awful to solder MPU6050.

burnd

I failed to mill it nice and solder it. so I tried with commercial MPU6050 breakout board (GY521).
Arduino Code : MPU6050test.ino
Library : Jeff Rowberg has made an I2C lib: http://www.i2cdevlib.com/devices/mpu6050
Reference : http://playground.arduino.cc/Main/MPU-6050
Wire connection : SCL - A5, SDA - A4, INT - D2

Test with Hello Bus

I followed the tutorial with Neil's board and succeed it.