Change serial commands to control characters, send everything else to ACIA (6850) input buffer

src/acia6850.c

@@ -1,3 +1,4 @@
+#include <stdbool.h>
 #include <libopencm3/usb/usbd.h>
 #include <libopencm3/usb/cdc.h>
 
@@ -20,14 +21,36 @@ extern usbd_device *usbd_dev;
 #define RDRF (1 << 0)
 #define TDRE (1 << 1)
 
+
+static char input[256];
+static int input_index = 0;
+static int input_processed_index = 0;
+
+void process_serial_input_byte(char b) {
+    input[input_index++] = b;
+    input_index %= sizeof(input);
+}
+
+
 uint8_t read6850(uint16_t address) {
 	switch(address & 1) {
-		case ACIAStatus:
-            return TDRE; // writable
+		case ACIAStatus: {
+            // Always writable
+            uint8_t flags = TDRE;
+
+            // Readable if there is pending user input data which wasn't read
+            if (input_processed_index < input_index) flags |= RDRF;
+
+            return flags;
 			break;
-		case ACIAData:
-            // TODO: read buffer from serial port
+        }
+		case ACIAData: {
+            char data = input[input_processed_index++];
+            input_processed_index %= sizeof(input);
+
+            return data;
 			break;
+        }
 		default:
             break;
 	}

src/cdcacm.c

@@ -189,7 +189,8 @@ void cdcacm_send_chunked_blocking(char *buf, int len, usbd_device *dev) {
 	} while (bytes_remaining > 0);
 }
 
-extern char *process_serial_command(char *buf, int len);
+extern char *process_serial_command(char b);
+extern void *process_serial_input_byte(char b);
 
 static void usbuart_usb_out_cb(usbd_device *dev, uint8_t ep)
 {
@@ -198,9 +199,6 @@ static void usbuart_usb_out_cb(usbd_device *dev, uint8_t ep)
 	char buf[CDCACM_PACKET_SIZE];
 	char reply_buf[256];
 
-	static char typing_buf[2048] = {0};
-	static int typing_index = 0;
-
 	int len = usbd_ep_read_packet(dev, CDCACM_UART_ENDPOINT,
 					buf, CDCACM_PACKET_SIZE);
 
@@ -214,21 +212,19 @@ static void usbuart_usb_out_cb(usbd_device *dev, uint8_t ep)
 		if (buf[i] == '\r') reply_buf[j++] = '\n';
 		reply_buf[j++] = buf[i];
 
-		typing_buf[typing_index++] = buf[i];
-
-		if (buf[i] == '\r' || buf[i] == '\n') {
-			char *response = process_serial_command(typing_buf, typing_index);
-			typing_index = 0;
+		char *response = process_serial_command(buf[i]);
+		if (response) {
+			reply_buf[j++] = '\r';
+			reply_buf[j++] = '\n';
 
 			for (size_t k = 0; k < strlen(response); ++k) {
 				reply_buf[j++] = response[k];
 			}
 
-			// prompt
 			reply_buf[j++] = '\r';
 			reply_buf[j++] = '\n';
-			reply_buf[j++] = '>';
-			reply_buf[j++] = ' ';
+		} else {
+			process_serial_input_byte(buf[i]);
 		}
 	}
 

src/main.c

@@ -103,27 +103,25 @@ static void usb_reset()
 	paused = false;
 }
 
-char *process_serial_command(char *buf, int len) {
-	(void) len;
-
-	if (buf[0] == 'v') {
+char *process_serial_command(char b) {
+	if (b == '\x16') { // ^V
 		return "Pill 6502 version " FIRMWARE_VERSION;
-	} else if (buf[0] == 'p') {
+	} else if (b == '\x10') { // ^P
 		paused = !paused;
 		return paused ? "paused" : "resumed";
-	} else if (buf[0] == 'r') {
+	} else if (b == '\x12') { // ^R
 		reset6502();
 		paused = false;
 		return "reset";
-	} else if (buf[0] == 't') {
+	} else if (b == '\x14') { // T
 		static char buf[64];
 		snprintf(buf, sizeof(buf), "%ld ticks\r\n%ld instructions", clockticks6502, instructions);
 		return buf;
-	} else {
-		return "invalid command, try ? for help";
+	} else if (b == '\x07') { // G
+		return "^V=version ^R=reset ^P=pause ^T=ticks ^G=help";
 	}
 
-	return "";
+	return NULL;
 }
 
 static void setup_clock(void) {