networking and communications

For this topic another board similar to the one made in the input devices week was assembled, with a small alteration - a couple of extra rdx tdx pins - to allow networking (you can see the layout in the img below) and the adapter cable to link it to the previously assembled board, the one used on the input and output devices weeks. The adapter had to be made so as to link the two different communications ports of the two boards. I uploaded Neal's “hello.bus.45.c” once more adapted to my board's specifications and it worked pretty well with the led signals, as you can see in the video, although wen I tried to move up to motor control the results were less enthusiastic.

//
//
// 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 PORTA
#define led_direction DDRA
#define led_pin (1 << PA2)

#define serial_port PORTA
#define serial_direction DDRA
#define serial_pins PINA
#define serial_pin_in (1 << PA0)
#define serial_pin_out (1 << PA1)

#define node_id '2'

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);
}
}
}

Here you can see that the LED from the activated node blinks twice.