634 Serial Display startup problems


New member
I am using the 634 serial lcd module. I have interfaced it to a microcontroller and communicate with it at 19k baud through a wire soldered to the pad on the display itself. The grounds are common.

It was working properly initially for a couple days and recently it seems to be having problems on startup. When I power up the system (MCU-LCD) the micro runs fine and executes code, but the display doesn’t show anything. The backlight is on and nothing else shows. I can alleviate this problem by turning it on and off a few times until it starts working, but this shouldn’t be so.

Should I wait a set duration of time after power-up before sending instructions to the display? In debugging my controller, the code “ran away” a few times and I am afraid that “junk” commands may have been sent to the display. Is it possible that these commands could have messed up the firmware of the display? Is it possible to reset the firmware of the display to its initial state?

Please help.
Looking for additional LCD resources? Check out our LCD blog for the latest developments in LCD technology.
USB LCD Displays - Graphic and Character LCDs with a Keypad

CF Tech

Send over the "Control the Boot Screen" command:


That will tell the display to ignore the EEPROM.