output devices

For output device I choose a DC motor. To control it, I used my input-output board made at the input devices week. I started with Neal's “hello.H-bridge.44.DC.c” program, changing the pins and ports definitions according to my board, and uploaded it to the ATTiny44. The initial movements had little amplitude and high speed making it more a vibration. More tuning was needed to make it work. I tried various settings of delays and PWM_count to discover in what direction I had to make the changes, ending up with the program below. The result can be seen in video at the bottom.

//
//
// hello.H-bridge.44.DC.c
//
// H-bridge DC motor hello-world
//
// Neil Gershenfeld
// 11/18/12
//
// (c) Massachusetts Institute of Technology 2012
// Permission granted for experimental and personal use;
// license for commercial sale available from MIT.
//

#include <avr/io.h>
#include <util/delay.h>

#define output(directions,pin) (directions |= pin) // set port direction for output
#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 on_delay() _delay_us(50) // PWM on time
#define fast_off_delay() _delay_us(1) // PWM fast off time
#define medium_off_delay() _delay_us(3) // PWM medium off time
#define slow_off_delay() _delay_us(5) // PWM slow off time
#define PWM_count 20000 // number of PWM cycles
#define cycle_count 5 // number of speed cycles

#define bridge_port PORTA // H-bridge port
#define bridge_direction DDRA // H-bridge direction
#define IN1 (1 << PA3) // IN1
#define IN2 (1 << PA2) // IN2

int main(void) {
//
// main
//
static uint16_t count;
static uint8_t cycle;
//
// set clock divider to /1
//
CLKPR = (1 << CLKPCE);
CLKPR = (0 << CLKPS3) | (0 << CLKPS2) | (0 << CLKPS1) | (0 << CLKPS0);
//
// initialize H-bridge pins
//
clear(bridge_port, IN1);
output(bridge_direction, IN1);
clear(bridge_port, IN2);
output(bridge_direction, IN2);
//
// main loop
//
while (1) {
for (cycle = 0; cycle < cycle_count; ++cycle) {
//
// turn forward slow
//
clear(bridge_port, IN1);
set(bridge_port, IN2);
for (count = 0; count < PWM_count; ++count) {
set(bridge_port, IN2);
on_delay();
clear(bridge_port, IN2);
slow_off_delay();
}
//
// turn reverse slow
//
clear(bridge_port, IN2);
set(bridge_port, IN1);
for (count = 0; count < PWM_count; ++count) {
set(bridge_port, IN1);
on_delay();
clear(bridge_port, IN1);
slow_off_delay();
}
}
for (cycle = 0; cycle < cycle_count; ++cycle) {
//
// turn forward medium
//
clear(bridge_port, IN1);
set(bridge_port, IN2);
for (count = 0; count < PWM_count; ++count) {
set(bridge_port, IN2);
on_delay();
clear(bridge_port, IN2);
medium_off_delay();
}
//
// turn reverse medium
//
clear(bridge_port, IN2);
set(bridge_port, IN1);
for (count = 0; count < PWM_count; ++count) {
set(bridge_port, IN1);
on_delay();
clear(bridge_port, IN1);
medium_off_delay();
}
}
for (cycle = 0; cycle < cycle_count; ++cycle) {
//
// turn forward fast
//
clear(bridge_port, IN1);
set(bridge_port, IN2);
for (count = 0; count < PWM_count; ++count) {
set(bridge_port, IN2);
on_delay();
clear(bridge_port, IN2);
fast_off_delay();
}
//
// turn reverse fast
//
clear(bridge_port, IN2);
set(bridge_port, IN1);
for (count = 0; count < PWM_count; ++count) {
set(bridge_port, IN1);
on_delay();
clear(bridge_port, IN1);
fast_off_delay();
}
}
}
}

here we can see the controler making the motor turning back foward in difrent velocities.