Start up Problem with CFA-735 connected with TTL serial.


New member
New to using your products. After Power up the display seems to not work until a large # of characters is sent to the display. Currently I am using the PING command:
$00,$14,$30,$31,$32,$33,$34,$35,$36,$37,$38,$39,$40,$41,$42,$43,$44,$45,$46,$47,$48,$49,ck <Hex characters, ck is checksum on end of command.

If I send this command 9 times then the display start talking back with the correct response and from that moment on it will continue to work correctly until I re power the unit. If I make the command shorter it takes more of them to get the display talking back so it seems it is tied to the # of characters sent to the display. I know the checksum is correct because sending the command after the display start talking works like it should. Any suggestions as to what to look for?
Looking for additional LCD resources? Check out our LCD blog for the latest developments in LCD technology.
What is the full model number?
What are you using to send the commands?
Have you checked that the data is actually reaching the input of the module during the "does not work" time?
Is the result the same using commands other than PING?
USB LCD Displays - Graphic and Character LCDs with a Keypad


New member

Sending data from an Embeded 68HC11 system using the TTL level serial input on H1 - 1 and 2 with +5 and ground going to 16 and 15.

When sending the data I checked with an oscilloscope and there is input to the CFA735 and no response from it. If I press one of the keys I do get output from the CFA735 and it is captured by the control board.

I did try sending the Clear screen command 1st but nothing happens on the display. Then I sent the ping command the 9 times and the screen then finally clears and I recieve the response from the display for all the commands that I sent.

As I stated before the only issue I have is when I power up the system it does not respond to any commands until I send many characters to it. I can use it this way with this work around at this time sense there is no external problem from a customer stand point. It seems to operate per the manual after this initialization problem.

CF Mark

It sounds like you have a problem with junk bytes being received by the CFA735 on power-up, before you try sending init commands.
If the CFA735 receives what appears to be a valid command byte & length byte, it'll wait for the rest of the packet before then responding to other commands.

For example, if junk bytes 0x00,0xFF are received, the CFA735 will then expect 255 bytes of data followed by the two CRC bytes.
There is no way to stop the CFA735 expecting this data. The only way to resume proper coms is to continue sending ping commands until you do get a reply.

So the best fool-proof method of first initializing coms with a CFA735 (or any of the other packet based modules) is to send ping packets until you do get a reply.