How to determine if display has reset

LK/ELK/VK/PK/OK/MX/GLK/EGLK/GVK/GLT Series

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Dale Ward
LCD?
Posts: 3
Joined: Mon Apr 19, 2010 8:35 pm

How to determine if display has reset

Post by Dale Ward » Mon Apr 19, 2010 8:51 pm

Hi. I am using the LK204, serial (rs232) mode attached to another embedded controller. It is possible during use that the LCD will loose power while the controller does not. What I would like to do is be able to send a command (rs232) to the LCD, and know that the LCD has had a power reset, allowing me on the controller to reinit the LCD, and redisplay any message. But I cannot find any way of reading any of the volatile parameters, or any other trick to find this out. Is there any undoc. command that allows reading of the ram of the LCD to check for power reset?
Thanks
Dale

Clark
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Post by Clark » Wed Apr 21, 2010 2:51 pm

Hi Dale,

I understand you have our display and your controller in a closed system, our display being more susceptible to a loss of power, you'd like to check in our display to see if it's been reset.

Unfortunately, I don't believe there is an easy way to do this using our standard display, documented or otherwise. It is possible to read out the display EEPROM, however, this will only tell you when memory has been corrupted; being ROM it will not change when power is cycled.

An ideal solution would be to ensure that the display is constantly receiving the correct input power. A regulator inline or one of our extended voltage displays with a built-in regulator may help.

~Troy
Troy Clark
Design & Development
Matrix Orbital

Dale Ward
LCD?
Posts: 3
Joined: Mon Apr 19, 2010 8:35 pm

Post by Dale Ward » Wed Apr 21, 2010 6:02 pm

Hi Troy,
Thanks for the reply. My problem is that the LCD may not derive its power from the same source as the controller, and as a further complication, the overall power supply is usually from a vehicle which can (when start/cranking) do some weird things to the supply voltage for milliseconds. In this environment we do not like to assume that the LCD is in a given state, we prefer to ask it. I will have a play with the GPO's and see if I can loop one of these back or something, but if you could add a read (flag set at startup, which is cleared by this read) command, that would be neat.
Dale

Clark
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Post by Clark » Fri Apr 23, 2010 2:43 pm

Hi Dale,

No worries, sorry the existing functions on our standard unit won't really work for your project. In your application, a response from the display after it has lost and regained power would probably be ideal. This is something that we have done as a custom for one of our larger OEM customers, and after discussing with our firmware designer may be something that we bring to more units in the future.

Also, while speaking with the firmware designer here, the possibility of using an ADC pin on your controller to monitor the power line going to our display came up. Obviously I'm not terribly familiar with your project, but this may be a good solution for the resetting issue.

~Troy
Troy Clark
Design & Development
Matrix Orbital

Dale Ward
LCD?
Posts: 3
Joined: Mon Apr 19, 2010 8:35 pm

Post by Dale Ward » Mon Apr 26, 2010 9:29 pm

Hi Troy,
We had the issue that cable looms were already made, so I preferred a solution that didnt involve changing the wiring between the units. I have implemented a change where I set the GPO 1 on powerup to 5v (the default of this output), and this turns on a bc549, which is wired across one col/row pin to simulate a key press. So each powerup we should see a keypress (an 'E'). I then reset that GPO1, clearing the keypress, and the device is now ready for use. In normal operation, any time I see the 'E' keypress, I know that the device has reset, and the GPO1 is now high. I then clear this. Seems to work reliably so far. Thanks for your assistance.
Dale

Clark
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Post by Clark » Tue Apr 27, 2010 9:19 am

No worries Dale, it looks like you've come up with a great solution for your application, and maybe even a few other developers who are faced with a similar situation.

~Troy
Troy Clark
Design & Development
Matrix Orbital

chris@dtscom.net
LCD?
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Joined: Wed Sep 22, 2010 8:17 am

Post by chris@dtscom.net » Wed Sep 22, 2010 8:49 am

Dale,

Why not hook the power supply for the LCD through a MOSFET so you can ensure a reset has occurred. The embedded controller would control the MOSFET. This will allow you to reset the device for a few ms or even seconds, and then bring the device back online when you are ready to.

Clark
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Post by Clark » Wed Sep 22, 2010 11:25 am

Hey Chris,

That's a great solution for controlling power to the display, while Dale has come up with a simple way to monitor power to the display. Both are great ideas to have up here for other users, thanks guys.

~Troy
Troy Clark
Design & Development
Matrix Orbital

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