debug works!

src/keyboard/controller.c

@@ -1211,6 +1211,61 @@ int8_t usb_extra_consumer_send() {
 // debug
 // --------------------------------------------------------
 
+// transmit a character.  0 returned on success, -1 on error
+int8_t usb_debug_putchar(uint8_t c) {
+  static uint8_t previous_timeout = 0;
+  uint8_t timeout, intr_state;
+
+  // if we're not online (enumerated and configured), error
+  if (!usb_configuration)
+    return -1;
+  // interrupts are disabled so these functions can be
+  // used from the main program or interrupt context,
+  // even both in the same program!
+  intr_state = SREG;
+  cli();
+  UENUM = DEBUG_TX_ENDPOINT;
+  // if we gave up due to timeout before, don't wait again
+  if (previous_timeout) {
+    if (!(UEINTX & (1 << RWAL))) {
+      SREG = intr_state;
+      return -1;
+    }
+    previous_timeout = 0;
+  }
+  // wait for the FIFO to be ready to accept data
+  timeout = UDFNUML + 4;
+  while (1) {
+    // are we ready to transmit?
+    if (UEINTX & (1 << RWAL))
+      break;
+    SREG = intr_state;
+    // have we waited too long?
+    if (UDFNUML == timeout) {
+      previous_timeout = 1;
+      return -1;
+    }
+    // has the USB gone offline?
+    if (!usb_configuration)
+      return -1;
+    // get ready to try checking again
+    intr_state = SREG;
+    cli();
+    UENUM = DEBUG_TX_ENDPOINT;
+  }
+  // actually write the byte into the FIFO
+  UEDATX = c;
+  // if this completed a packet, transmit it now!
+  if (!(UEINTX & (1 << RWAL))) {
+    UEINTX = 0x3A;
+    debug_flush_timer = 0;
+  } else {
+    debug_flush_timer = 2;
+  }
+  SREG = intr_state;
+  return 0;
+}
+
 // immediately transmit any buffered output.
 void usb_debug_flush_output(void) {
   uint8_t intr_state;
@@ -1227,3 +1282,15 @@ void usb_debug_flush_output(void) {
   }
   SREG = intr_state;
 }
+
+void debug_print_ptr(const char *s) {
+  char c;
+
+  while (1) {
+    c = pgm_read_byte(s++);
+    if (!c) { break; }
+    if (c == '\n') { usb_debug_putchar('\r'); }
+    usb_debug_putchar(c);
+  }
+  usb_debug_flush_output();
+}

src/keyboard/controller.h

@@ -8,6 +8,8 @@
 
 #pragma once
 
+#define USB_DEBUG_HID
+
 #include <stdbool.h>
 #include <stdint.h>
 #include <avr/io.h>
@@ -203,5 +205,10 @@ extern uint16_t consumer_key;
 
 extern volatile uint8_t debug_flush_timer;
 
-#define usb_debug_putchar(c)
-void usb_debug_flush_output(void);	// immediately transmit any buffered output
+// this macro allows you to write print("some text") and
+// the string is automatically placed into flash memory :)
+#define debug_print(s) debug_print_ptr(PSTR(s))
+void debug_print_ptr(const char *s);
+
+int8_t usb_debug_putchar(uint8_t c);	// transmit a character
+void usb_debug_flush_output(void);  	// immediately transmit any buffered output