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