Silly interactive loop to test things out.

main.c

@@ -19,6 +19,7 @@
 #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))
 
@@ -44,8 +45,67 @@ 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!\n");
+	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;
 }