Added tinybasic

main.c

@@ -45,6 +45,23 @@ static void uart_putc(char c)
     uart_kick();
 }
 
+/* Stable monitor ABI implementations, reached through the jump table at C050. */
+void monitor_uart_putc(char c)
+{
+    uart_putc(c);
+}
+
+uint8_t monitor_uart_getc(void)
+{
+    char c;
+    uint8_t received;
+
+    disable_interrupts();
+    received = buffer_dequeue(&rx_buf, &c);
+    enable_interrupts();
+    return received ? (uint8_t)c : 0;
+}
+
 static void uart_puts(const char *s)
 {
     while (*s) uart_putc(*s++);
@@ -182,6 +199,7 @@ static void print_help(void)
         "  I|IN port                 Read an I/O port\r\n"
         "  O|OUT port byte           Write an I/O port\r\n"
         "  G|GO address              Execute code; RET returns here\r\n"
+        "  B|BASIC                   Start Tiny BASIC at D000\r\n"
         "  H|HELP|?                  Show this help\r\n");
 }
 
@@ -265,6 +283,16 @@ static void command_out(uint8_t argc, char **argv)
     uart_puts("OK\r\n");
 }
 
+static void execute_address(uint16_t address)
+{
+    uart_puts("Executing at ");
+    print_hex16(address);
+    uart_puts("...\r\n");
+    uart_flush();
+    jump_to(address);
+    uart_puts("Returned to monitor\r\n");
+}
+
 static void command_go(uint8_t argc, char **argv)
 {
     uint16_t address;
@@ -273,12 +301,16 @@ static void command_go(uint8_t argc, char **argv)
         uart_puts("Usage: G address\r\n");
         return;
     }
-    uart_puts("Executing at ");
-    print_hex16(address);
-    uart_puts("...\r\n");
-    uart_flush();
-    jump_to(address);
-    uart_puts("Returned to monitor\r\n");
+    execute_address(address);
+}
+
+static void command_basic(uint8_t argc)
+{
+    if (argc != 1) {
+        uart_puts("Usage: B\r\n");
+        return;
+    }
+    execute_address(0xd000);
 }
 
 static void execute_line(char *line)
@@ -300,6 +332,8 @@ static void execute_line(char *line)
         command_out(argc, argv);
     } else if (strings_equal(argv[0], "g") || strings_equal(argv[0], "go")) {
         command_go(argc, argv);
+    } else if (strings_equal(argv[0], "b") || strings_equal(argv[0], "basic")) {
+        command_basic(argc);
     } else {
         uart_puts("Unknown command; type HELP\r\n");
     }