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/* Run minicom -D /dev/ttyACM0 -b 9600 */
#include "stm32_unict_lib.h"
#include <stdio.h>
#define MAX 128
/* Slide 3/13 */
struct t_tx_state {
uint8_t data;
uint8_t buffer[MAX];
int head, tail, data_count;
int bit_count;
int start;
} tx_state;
/*
* 9600 interruputs per seconds
* 84e6/9600 = 8750
*/
void
init_periph()
{
GPIO_init(GPIOA);
GPIO_config_output(GPIOA, 2);
GPIO_write(GPIOA, 2, 1);
TIM_init(TIM2);
TIM_config_timebase(TIM2, 1, 8750);
TIM_set(TIM2, 0);
TIM_on(TIM2);
TIM_enable_irq(TIM2, IRQ_UPDATE);
tx_state.start = 0;
tx_state.bit_count = 0;
tx_state.head = tx_state.tail = tx_state.data_count = 0;
}
void
send_byte(uint8_t c)
{
/* First wait the end of the trasmission */
while (tx_state.data_count == MAX) { }
tx_state.buffer[tx_state.head] = c;
tx_state.head = (tx_state.head + 1) % MAX;
tx_state.data_count++;
tx_state.start = 1;
}
int
__io_putchar(int ch)
{
send_byte(ch);
return 0;
}
int
main()
{
int i;
init_periph();
i = 0;
for (;;) {
printf("Hello world, %d\n\r", i++);
delay_ms(100);
}
return 0;
}
void
TIM2_IRQHandler(void)
{
if (TIM_update_check(TIM2)) {
if (tx_state.start) {
switch (tx_state.bit_count) {
case 0:
GPIO_write(GPIOA, 2, 0);
break;
case 9:
case 10:
GPIO_write(GPIOA, 2, 1);
break;
default:
/* Data bit */
GPIO_write(GPIOA, 2, tx_state.data & 1); // TX B0
tx_state.data >>= 1;
}
tx_state.bit_count++;
if (tx_state.bit_count == 11) {
--tx_state.data_count;
if (tx_state.data_count > 0) {
tx_state.data = tx_state.buffer[tx_state.tail];
tx_state.tail = (tx_state.tail + 1) % MAX;
} else {
tx_state.start = 0;
}
tx_state.bit_count = 0;
}
}
TIM_update_clear(TIM2);
}
}
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