Serial 634 Communication Issues


New member

I purchased a Serial 634 LCD Screen a while ago, and it has been in storage. I recently attempted to use it again, and I believe there is some kind of problem.

I downloaded and used the WinTest2.0 program and when the serial port is initialized, the screen boots up and shows the usual splash screen:
Crystalfontz America
KD204-634v2.0 19.2Kb
After this splash scren dissappears, the display has a flashing black cursor on the top left. When I send a command from the WinTest program nothing appears on the screen.

I have made sure that the data transfer rate within windows is set for 19200 as well as the dip-switches on the back of the unit are set to 19200.

Any help you can provide would be appreciated.

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CF Tech

Well, I would think that would work.

We can have you send it back to here of course, but it might be easier if you can see if you can get it working on a computer with a "real" serial port. If that is not possible, you can write support(at]crystalfontz{dot]com (edit to '@' & '.') and request an RMA.


New member
If using XP, go to 'Start' button/Control Panel/Performance and Maintenance/System
Select the 'hardware' tab, then the 'Device Manager' button

Now, once in this location perform a properties check on the USB to Serial adaptor and see what com port it is on. If its on something daft like 8/9 like they often do then its probably that. My 634 is on com port 3 but then I have 2 other modules connected also.

I spotted this connecting a USB to Serial Adaptor to my laptop and using a program that was limited to com1 to 4 to send data to a satellite receiver. The program was sending through com port 1 but the adaptor was using com port 8 or 9 depending which USB port I plugged into. I changed it to com 1 and all started working. Might not be the answer but its worth checking out.

Hope this helps and solves the problem,

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