matrix scan & default keymap

print.c

@@ -58,5 +58,9 @@ void phex16(unsigned int i)
 }
 
 
-
-
+void pbin(unsigned char c)
+{
+    for (int i=7; i>=0; i--) {
+        usb_debug_putchar((c & (1<<i)) ? '1' : '0');
+    }
+}