Data Lock On an LK202-25-WB

[myfj1200]

I have an LK202-25-WB running off of a PIC 16F877A through a MAX232. This display is only for display, There is no Keypad attached to this.
I am having a problem with line noise being picked up and "reprogramming" this display.

I have already tested locking down this display using the value of 128 (total lockdown no display) and 64 (Lockdown with no control character support) This works correctly.

I am looking to lock down with a value of 24 = 00011000 Which if i'm reading this correctly should lock down all panel settings and still allow control characters but lock out any lighting & panel settings. This doesn't seem to work. I've also tried values of 16 & 8 individually with no success.

The value of 64 seems to work correctly for what I need with the exception of position control characters. I do still need that to work.

With these settings locked down even if line noise is picked up the display will simply reset itself on the next cycle (minimal display garbage is acceptable)

Any help would be appreciated.

[Raquel]

Hello,

Thanks for posting on the forum.

Can you please tell me more of the 'noise' that gets to the display? Are these garbage characters that show up on the display? I wonder about 'reprogramming' the display; does the display redeem itself with cycling the power?

You will need to make sure that the display gets good clean power, and try to free it from the noise in your system. We can look at the route of locking the display, but this is not quite a solution but just a band-aid.

Please tell me more of the situation and symptom; hopefully we can find a good solution.

Thanks,

[myfj1200]

For a little background on this issue I have had similar issues Likely related, check this thread:
http://www.lcdforums.com/forums/viewtop ... 1185#21185

The power supply is a very stable (confirmed) Switching DC supply.

As for the symptoms: Prior to locking down the baud rate (data lock) That was the first thing to go, Once the rate was set to a different speed there would only be garbage displayed using any standard speed. Upon power reset the incorrect settings would be retained. The only way to establish communications with the display was to use the factory default jumper then using "Uproject" to "Remember" the settings. After this the display would work fine again. Sometimes for a day Sometimes for a few months.

The display in this application is also located within a few inches of a heavy duty (shielded) servo drive motor and the cabling is also run fairly close. If anywhere I would suspect this is where the noise is coming from. Both cables are using shielded cable & everything has been placed as far apart as functionally possible. The display is more of a convenience factor to notify you of what part of the program you're in. But still nice to have.

I am aware that this is sort of a Band-Aid not so much a solution yet in this case a Band-Aid might just be all that is needed. I would like to lock down everything except for Serial Text Display & Character Position Control.

[myfj1200]

Also, If you unplug the connector from the LCD Display when it is not displaying properly and connect it to a Laptop running HyperTerminal the correct info comes through.
(the control characters look like garbage though)

[Raquel]

Hi Joe,

Unfortunately, position character command (254 / 71 / col / row) is still a command, and so using setting lock 64 (command lock) will make the display ignore this command.

What you can do then is to unlock the display using command 254 / 202 / 245 / 160 / 0 then send the position character command 254 / 71 / col / row /. You will then have to re-lock the display when you are done.

As per garbage on control characters, the display only implements the following control characters:
0x08 Backspace
0x0C Clear screen / New page
0x0D Carriage return
0x0A Line feed / New line

Thanks,