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#include <pic16f84a.h>
typedef unsigned char uint8_t;
__sfr __at(0x70) UART_TX;
__sfr __at(0x71) UART_RX;
__sfr __at(0x72) UART_STATUS;
/*
* how many OVF per refresh of the screen
*/
#define OVF_PER_REFRESH 80
#define DIR_UP 0
#define DIR_DOWN 1
#define DIR_LEFT 2
#define DIR_RIGHT 3
uint8_t direction;
uint8_t position[2];
static volatile uint8_t ovf_count = 0;
void isr(void) __interrupt(0) {
if (INTCON & 0x04) { /* T0IF = bit 2 */
ovf_count++;
INTCON &= ~(uint8_t)0x04;
}
}
static void uart_send(uint8_t b) {
while (UART_STATUS & 0x01);
UART_TX = b;
}
static void uart_puts(const char *s) {
while (*s) uart_send((uint8_t)*s++);
}
static uint8_t uart_recv(void) {
if (UART_STATUS & 0x02)
return 0; /* rx_empty: nothing to read */
return UART_RX; /* reading pops the FIFO */
}
static uint8_t uart_getc(void) {
while (UART_STATUS & 0x02);
return UART_RX;
}
static void handle_input(void) {
uint8_t c = uart_recv();
if (c != 0x1B)
return;
if (uart_getc() != '[')
return;
switch (uart_getc()) {
case 'A': direction = DIR_UP; break; /* ESC [ A */
case 'B': direction = DIR_DOWN; break; /* ESC [ B */
case 'C': direction = DIR_RIGHT; break; /* ESC [ C */
case 'D': direction = DIR_LEFT; break; /* ESC [ D */
}
}
static void update_position(void) {
switch (direction) {
case DIR_UP: position[1]--; break;
case DIR_DOWN: position[1]++; break;
case DIR_LEFT: position[0]--; break;
case DIR_RIGHT: position[0]++; break;
}
}
static void print_uint8(uint8_t v) {
uint8_t started = 0;
if (v >= 200) { uart_send('2'); v -= 200; started = 1; }
else if (v >= 100) { uart_send('1'); v -= 100; started = 1; }
{
uint8_t t = '0';
while (v >= 10) { v -= 10; t++; }
if (started || t != '0') uart_send(t);
}
uart_send(v + '0');
}
static void render(void) {
uart_puts("\x1B[H"); /* cursor home */
uart_puts("pos: ");
print_uint8(position[0]);
uart_puts(", ");
print_uint8(position[1]);
uart_puts("\r\n");
}
void main(void) {
OPTION_REG = 0x07;
TMR0 = 0;
INTCON = 0xa0;
direction = DIR_RIGHT;
position[0] = 10;
position[1] = 5;
uart_puts("\x1B[2J\x1B[H");
uart_puts("snake\r\n");
uart_puts("-----------\r\n");
while (1) {
ovf_count = 0;
while (ovf_count < OVF_PER_REFRESH);
handle_input();
update_position();
render();
PORTA ^= 0x01;
}
}
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