• We recently switched our forum platform. If you experience any issues please email support@crystalfontz.com

633 Serial Problem


New member

I think my 633 is dying.

It started when the last two character positions only displayed solid blocks no matter what I sent to it.

Using CrystalControl it seems to not display any test but just flicker at high speed. However, if I tilit it to certain severe angles (about 70 degrees+) I can read the text.

If I close CyrstalControl and use WinTest the LCD does not light up at all. The ping & clear LCD commands work.

Setting the LCD line text fails with an error -

C=7( 7 = LCD Line 1),L=7,D="Welcome",CRC=0x264C
C=199(Error: Set LCD 1),L=0,D="",CRC=0x4188E5

A reboot results in the following command/response pair.

C=5( 5 = Reboot),L=0,D="",CRC=0x71FF
C=197(Error: Reboot),L=0,D="",CRC=0x41BB55

Can you shed any light on this.


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

To be sure, you are using 633_WinTest, right?

Please check the command syntax in the data sheet. For instance, Command 7 requires 16 bytes and the reboot command requires specific parameters.

Then try using the contrast slider.
Reboot data length = 3

The reason you're probably having trouble is that the reboot command has 3 data bytes, and it looks like you're just sending it data=''.

Check the manual, but I think the data are [8,18,99]


New member
Thanks guys,

You are course correct. I was presuming that the test program was going to send the correct data bytes for reboot etc.

I tried it programatically and it all works.

Well except that the last two characters on both lines always come out as solid blocks and not the correct text. They clear ok but whenevr I write to them the first 14 chars are okay but 15 & 16 show as solid blocks.