Matrix Orbital Corp

Hi all,

I'm trying to switch my LK204-25 Display over to TTL as that is the only thing my controller can output on the RS-232. The manual is a little vague on what jumpers you are suppose to remove from the 232 section. There are 3 and I believe one would be the ground jumper and you would need to keep that. Is there anyone that has ran into this problem with this and has the correct way to accomplish this task. I have been working on getting the controller and display to talk together and this is what I believe it is. Thank you for any advise and a quick response. If you need any other info let me know.

Anthony

Hello Anthony,

Thank you for posting on the forum.

To put the LK204-25 (PCB 2.0) to TTL, you will need to take all three 0-Ohm resistors on 232 out and put 2 0-ohm (or just solder blobs) on the TTL pads.

Please let me know how it turns out.

We have taken these 3 0 ohm resistors out and placed solder jumpers on the 2 TTL jumpers but when we try to plug it in all that happens is the display goes blank and sometimes gets garbage. The RS-232 port also stops transmitting and recieving data.

Hello Anthony,

When you power up the module, you should see the MO start screen, unless it has been changed to something else, or even changed to blank, which can be the reason why you see blank screen.

As per the garbage characters, please make sure that you are communicating with the module at the right baud rate. The default baud rate is 19200 but then if it is possible that this has been changed as well, power off the module and put a jumper on pins 6 and 7 of the keypad connector (marked 'C1' and the pin to the left of it). Power the module back on, and it should be temporarily set to 19200.

"The RS-232 port also stops transmitting and recieving data." - I am not quite sure what you mean by this. If you see characters on the screen, the module is receiving data, just not at the right baud.

Please let me know how it turns out.

Hi Anthony,

This is strange behavior for the module. Can you double check the signal levels that you are attempting to send. TTL mode requires signal levels of 0-5V, and can be damaged if you attempt to send wrong voltage levels.

--
Jon

Hi again,

Ok I've now been able to connnect the display to the controller and have the controller talk back to it. The problem was that when I was using the TTL jumpers I was still using the RS-232 slot and it included the ground. I've switched over to the 4 pin connector with VCC and GND on the ends. There is now no ground between the controller and display, and it seems to be talking from the controller to the display. The only problem now is that I cannot get any signal from the keypad that is on the display. Is there something I'm missing or do I have to use the RS-232 connector to get the keypad to work properly. I'm gonna try a few other things and see what I can get. hope to hear from you guys soon. By the way thanks for the for the quick replies.

Hi Anthony,

First I will take a bit of time to let you know how our keypad works. Basically, when you short a Row pin with a column pin the display generates a keypress and then sends that keypress down the Tx line.

If you want to ensure that the display is generating a keypress you might have to switch it back to RS-232 mode, then connect it to a PC, and have hyper terminal watch the Serial port (using the correct baud of 19200, 1 stop bit, no parity, 8 bit communication). Every time you generate a keypress the keypress should be displayed on your console.

Another program that you can use for debugging is uProject. This program will allow you to test your keypad in the main section (once you have opened the com port).

Once you have confirmed that the display is indeed generating a keypress and transmitting it, then you may want to find out why your controller is unable to read it. It may be a simple matter of you clearing your input buffer before trying to read from it.

Please let me know if this helps.

--
Jon

Hi Anthony,

May I add on Jon's reply:
Make sure that the module is set to Auto Transmit. You can easily do this using uProject -> Main Tab -> Auto Transmit key presses.