Quadrotor from scratch
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111 lines
1.8 KiB

#define UARTBASE 0xE000C000
#define RBR 0x00
#define THR 0x00
#define DLL 0x00
#define DLM 0x04
#define IER 0x04
#define IIR 0x08
#define FCR 0x08
#define LCR 0x0c
#define LSR 0x14
#define SCR 0x1c
#define ACR 0x20
#define FDR 0x28
#define TER 0x30
#define REG(x) (((volatile unsigned char *)UARTBASE)[x])
#define U0THRE ((REG(LSR) & (1<<5))) /* UART0 transmitter holding register is empty */
#define U0DR ((REG(LSR) & (1<<0))) /* UART0 data ready */
#define PINSEL0 (*((volatile unsigned char *) 0xE002C000))
void init_uart(void)
{
REG(FDR) = 0x10; /* DivAddVal = 0, MulVal = 1 */
REG(LCR) = 0x80;
REG(DLM) = 0x00;
REG(DLL) = 0x08; /* 14745600 / (16*115200) */
REG(LCR) = 0x13;
REG(FCR) = 0x07;
PINSEL0 = 0x00000005; /* P0.0 and P0.1 assigned to UART */
}
void putch(char c) {
while (!U0THRE);
REG(THR) = c;
}
void putstr(char *s) {
while (*s) putch(*s++);
}
void putint(unsigned int n) {
char s[11];
int i;
i = 10;
s[i] = '\0';
do {
s[--i] = n % 10 + '0';
} while ((n /= 10) > 0);
putstr(s+i);
}
char getch(void) {
while (!U0DR);
return REG(RBR);
}
void reply(char *str)
{
putstr(str);
putstr("\r\n");
}
unsigned int count = 0;
int main(void) {
init_uart();
putstr("Your entire life has been a mathematical error... a mathematical error I'm about to correct!\r\n");
while (1) {
char c;
putstr("prompt> ");
c = getch();
if (c == 0x0a)
continue;
putch(c);
putstr("\r\n");
switch (c & 0xdf) {
case 0x0a:
case 0x0d:
break;
case 'A':
reply("apple");
break;
case 'C':
count++;
putstr("The current count is ");
putint(count);
reply(".");
break;
case 'H':
case '?':
reply("Help is not available. Try a psychiatrist.");
break;
default:
reply("Unrecognised command.");
break;
}
}
return 0;
}