13. Networking and Communications¶
The name could be quite scary , yet it wasn’t that much . Just kidding , it was a hell load of information !!
Group Assignment¶
Arduinos¶
A straight forward easy-looking connection between 2 arduinos .
We understood the concept and the code . It’s all Here.
I2C vs SPI¶
First , I did some research on communication protocols to understand the difference and be able to decide which one to use .
came across this Article it was very useful .
It seemed that I2C is less complicated especially in wiring , so I’m going for it .
Also , found a former student : Aby Michael documentation on I2C connection between Attiny 44 and Atmega 328 . It was very helpful .
I2C¶
Design¶
2 Boards of attiny 44 : teacher and student .
Used Kicad , getting quite handy around it by now . 2 simple boards with a button and led on each .
Milling and Soldering¶
Got the gcode from Fab Modules
Milled on a China Router 3040 using the OpenBuilds software .
Programming¶
One board will be the teacher and the other is the student .
The Led on student’s board blinks when it receives data .
Code for Teacher :
#include <Wire.h>
#define I2C_SLAVE_ADDR 0x26
int x = 0;
void setup() {
// Start the I2C Bus as Master
Wire.begin();
}
void loop() {
Wire.beginTransmission(9); // transmit to device #9
Wire.write(x); // sends x
Wire.endTransmission(); // stop transmitting
x++; // Increment x
if (x > 5) x = 0; // `reset x once it gets 6
delay(1000);
}
Code for Student :
#include <Wire.h>
#define ADDR 0x26 // i2c slave address (38)
#define LED1 10 // ATtiny PA3
void setup(){
pinMode(LED1 ,OUTPUT); // for verification
digitalWrite(4, HIGH); //pullup of SCL
digitalWrite(6,HIGH); //pullup of SDA
Wire.begin(ADDR);
delay(1000); // wait for a second
}
void loop(){
byte byteRcvd = 0;
if (Wire.available()){ // got I2C input!
byteRcvd = Wire.read(); // get the byte from master
// byteRcvd += 10; // add 10 to what's received
// Wire.read()(byteRcvd); // send it back to master
if(byteRcvd!=0){
digitalWrite(LED1, HIGH); //blue led= receive
delay(500);
//digitalWrite(LED1, LOW);
//delay(200);
}
}
}
Do you copy ?¶
Connections
Master board powered by FTDI cable .
Connected pins between boards as drawn , GND , VCC , SDA & SCK .
UART¶
my Instructor adviced me to make a UART protocol .
UART stands for Universal Asynchronous Receiver/Transmitter. It’s not a communication protocol like SPI and I2C, but a physical circuit in a microcontroller, or a stand-alone IC. A UART’s main purpose is to transmit and receive serial data.
Board¶
A bridge and 2 nodes ,
Node Design on kicad
Through Gimp
Fab Modules
Milled on MonoFab
Solder
Bridge Design on kicad
Through Gimp
Fab Modules
Milled on MonoFab
Solder
Programming¶
Code used
//
//
// hello.bus.45.c
//
// 9600 baud serial bus hello-world
//
// Neil Gershenfeld
// 11/24/10
//
// (c) Massachusetts Institute of Technology 2010
// Permission granted for experimental and personal use;
// license for commercial sale available from MIT.
//
#include <avr/io.h>
#include <util/delay.h>
#include <avr/pgmspace.h>
#include <string.h>
#define output(directions,pin) (directions |= pin) // set port direction for output
#define input(directions,pin) (directions &= (~pin)) // set port direction for input
#define set(port,pin) (port |= pin) // set port pin
#define clear(port,pin) (port &= (~pin)) // clear port pin
#define pin_test(pins,pin) (pins & pin) // test for port pin
#define bit_test(byte,bit) (byte & (1 << bit)) // test for bit set
#define bit_delay_time 100 // bit delay for 9600 with overhead
#define bit_delay() _delay_us(bit_delay_time) // RS232 bit delay
#define half_bit_delay() _delay_us(bit_delay_time/2) // RS232 half bit delay
#define led_delay() _delay_ms(100) // LED flash delay
#define led_port PORTB
#define led_direction DDRB
#define led_pin (1 << PB0)
#define serial_port PORTB
#define serial_direction DDRB
#define serial_pins PINB
#define serial_pin_in (1 << PB3)
#define serial_pin_out (1 << PB4)
#define node_id '0'
void get_char(volatile unsigned char *pins, unsigned char pin, char *rxbyte) {
//
// read character into rxbyte on pins pin
// assumes line driver (inverts bits)
//
*rxbyte = 0;
while (pin_test(*pins,pin))
//
// wait for start bit
//
;
//
// delay to middle of first data bit
//
half_bit_delay();
bit_delay();
//
// unrolled loop to read data bits
//
if pin_test(*pins,pin)
*rxbyte |= (1 << 0);
else
*rxbyte |= (0 << 0);
bit_delay();
if pin_test(*pins,pin)
*rxbyte |= (1 << 1);
else
*rxbyte |= (0 << 1);
bit_delay();
if pin_test(*pins,pin)
*rxbyte |= (1 << 2);
else
*rxbyte |= (0 << 2);
bit_delay();
if pin_test(*pins,pin)
*rxbyte |= (1 << 3);
else
*rxbyte |= (0 << 3);
bit_delay();
if pin_test(*pins,pin)
*rxbyte |= (1 << 4);
else
*rxbyte |= (0 << 4);
bit_delay();
if pin_test(*pins,pin)
*rxbyte |= (1 << 5);
else
*rxbyte |= (0 << 5);
bit_delay();
if pin_test(*pins,pin)
*rxbyte |= (1 << 6);
else
*rxbyte |= (0 << 6);
bit_delay();
if pin_test(*pins,pin)
*rxbyte |= (1 << 7);
else
*rxbyte |= (0 << 7);
//
// wait for stop bit
//
bit_delay();
half_bit_delay();
}
void put_char(volatile unsigned char *port, unsigned char pin, char txchar) {
//
// send character in txchar on port pin
// assumes line driver (inverts bits)
//
// start bit
//
clear(*port,pin);
bit_delay();
//
// unrolled loop to write data bits
//
if bit_test(txchar,0)
set(*port,pin);
else
clear(*port,pin);
bit_delay();
if bit_test(txchar,1)
set(*port,pin);
else
clear(*port,pin);
bit_delay();
if bit_test(txchar,2)
set(*port,pin);
else
clear(*port,pin);
bit_delay();
if bit_test(txchar,3)
set(*port,pin);
else
clear(*port,pin);
bit_delay();
if bit_test(txchar,4)
set(*port,pin);
else
clear(*port,pin);
bit_delay();
if bit_test(txchar,5)
set(*port,pin);
else
clear(*port,pin);
bit_delay();
if bit_test(txchar,6)
set(*port,pin);
else
clear(*port,pin);
bit_delay();
if bit_test(txchar,7)
set(*port,pin);
else
clear(*port,pin);
bit_delay();
//
// stop bit
//
set(*port,pin);
bit_delay();
//
// char delay
//
bit_delay();
}
void put_string(volatile unsigned char *port, unsigned char pin, PGM_P str) {
//
// send character in txchar on port pin
// assumes line driver (inverts bits)
//
static char chr;
static int index;
index = 0;
do {
chr = pgm_read_byte(&(str[index]));
put_char(&serial_port, serial_pin_out, chr);
++index;
} while (chr != 0);
}
void flash() {
//
// LED flash delay
//
clear(led_port, led_pin);
led_delay();
set(led_port, led_pin);
}
int main(void) {
//
// main
//
static char chr;
//
// set clock divider to /1
//
CLKPR = (1 << CLKPCE);
CLKPR = (0 << CLKPS3) | (0 << CLKPS2) | (0 << CLKPS1) | (0 << CLKPS0);
//
// initialize output pins
//
set(serial_port, serial_pin_out);
input(serial_direction, serial_pin_out);
set(led_port, led_pin);
output(led_direction, led_pin);
//
// main loop
//
while (1) {
get_char(&serial_pins, serial_pin_in, &chr);
flash();
if (chr == node_id) {
output(serial_direction, serial_pin_out);
static const char message[] PROGMEM = "node ";
put_string(&serial_port, serial_pin_out, (PGM_P) message);
put_char(&serial_port, serial_pin_out, chr);
put_char(&serial_port, serial_pin_out, 10); // new line
led_delay();
flash();
input(serial_direction, serial_pin_out);
}
}
}
Flashed the code and tested the nodes after they are connected through a bus .
Changed the node id for each board
for Bridge
#define node_id '0'
for Node 1
#define node_id '1'
for Node 2
#define node_id '2'
Using serial monitor in Arduino ..
Sending node 0 , node 1 , node 2
files¶
Download design files and code Here.