diff --git a/main.c b/main.c
index 3747d8a..8f3d154 100644
--- a/main.c
+++ b/main.c
@@ -119,31 +119,39 @@ structure shall also meet the requirements of CEA-861-D.
  */
 static uint16_t edid_length(void)
 {
+	puts("EDID check: ");
 	// check EDID 1.3/1.4 fixed pattern header
 	if (0x00 != edid[0] || 0xff != edid[1] || 0xff != edid[2] || 0xff != edid[3] || 0xff != edid[4] || 0xff != edid[5] || 0xff != edid[6] || 0x00 != edid[7]) {
+		puts("invalid header\r\n");
 		return 0;
 	}
 
 	if (1 == edid[18]) { // EDID 1.3/1.4 128-byte structure
 		if (checksum_ok(&edid[0], 128)) {
 			if (0 == edid[126]) { // no extension
+				puts("128 bytes\r\n");
 				return 128;
 			} else { // extension available
 				// the usual extension is CEA EDID Timing Extension (with extension tag 02), but we allow others
 				// no idea how more than 1 extension is supported
 				if (checksum_ok(&edid[128], 128)) {
+					puts("256 bytes (with extension)\r\n");
 					return 256;
 				} else {
+					puts("extension CRC error\r\n");
 					return 0; // EDID is broken
 				}
 			}
 		} else {
+			puts("CRC error\r\n");
 			return 0;
 		}
 	} else if (2 == edid[18]) { // EDID 2.0 256-byte structure
 		if (checksum_ok(&edid[0], 256)) {
+			puts("256 bytes (no extension)\r\n");
 			return 256;
 		} else {
+			puts("CRC error\r\n");
 			return 0;
 		}
 	}
@@ -245,15 +253,23 @@ void main(void)
 	IWDG->PR.fields.PR = IWDG_PR_DIV256; // set prescale to longest time (1.02s)
 	IWDG->KR.fields.KEY = IWDG_KR_KEY_REFRESH; // reset watchdog
 
+	puts("\r\nCuVoodoo HDMI firewall programmer ready\r\n");
+
 	// erase saved EDID when button is pressed on boot
 	if (0 == (RW_BUTTON_PORT->IDR.reg & RW_BUTTON_PIN)) { // button is pressed while booting
 		for (uint16_t i = 0; i < ARRAY_LENGTH(edid); i++) {
 			edid[i] = 0; // create empty EDID
 		}
 		ram_eeprom_blockprog(edid, ARRAY_LENGTH(edid)); // erase EDID
+		puts("EEPROM EDID erased\r\n");
 	}
 	load_edid(); // load EDID from EEPROM
 	bool edid_valid = (0 != edid_length()); // verify if EDID is valid
+	if (edid_valid) {
+		puts("EEPROM EDID valid\r\n");
+	} else {
+		puts("EEPROM EDID not valid\r\n");
+	}
 
 	rim(); // re-enable interrupts
 	bool action = false; // if an action has been performed
@@ -276,19 +292,24 @@ void main(void)
 				}
 				led_error = false; // reset error state
 				if (press_duration < 30) { // less than 3 sec
+					puts("read I²C EDID: ");
 					run_led_on(); // indicate we started
 					if (read_edid()) { // read EDID from I²C
+						puts(" OK\r\n");
 						edid_valid = (0 != edid_length()); // verify if EDID is valid
 						if (edid_valid) { // read EDID is valid
+							puts("I²C EDID valid\r\n");
 							IWDG_KR = IWDG_KR_KEY_REFRESH; // reset watchdog
 							led_error = !save_edid(); // save to EEPROM
 							IWDG_KR = IWDG_KR_KEY_REFRESH; // reset watchdog
 						} else { // read EDID is not valid
+							puts("I²C EDID not valid, reloading from EEPROM\r\n");
 							led_error = true; // indicate read error
 							load_edid(); // re-load EDID from EEPROM
 							edid_valid = (0 != edid_length()); // verify if EDID is valid
 						}
 					} else { // read error
+						puts("\r\n"); // error should have been printed
 						led_error = true; // indicate read error
 						load_edid(); // re-load EDID from EEPROM
 						edid_valid = (0 != edid_length()); // verify if EDID is valid
@@ -299,6 +320,7 @@ void main(void)
 					if (edid_valid) {
 						led_error = !write_edid(); // write EDID to I²C EEPROM
 					} else {
+						puts("\r\n"); // error should have been printed
 						led_error = true; // we can't program an invalid EDID
 					}
 				}