LK204-25 Display Locks Up and Freezes

jason · Post by **jason** » Thu Mar 31, 2005 11:44 am

Hello,

I've got about 20 LK204-25 displays that I know, over time, the couple that I've tried are locking up. The display will freeze with the last information that was sent to it.

-I'm using a Philips Micro LPC935 to drive the display.
-I'm using the I2C.
-Not using the GPO's.

....However, the Micro continues to work and I am able to continue without a problem except that the display stops updating.

I've checked to make sure that the data transmission is still alright going to the LCD display and it is.

Could this be a grounding issue?

Any advice would be great!

Thanks,

Jason

Miles · Post by **Miles** » Thu Mar 31, 2005 12:09 pm

Thank you for the post Jason.

Can you tell me what type of length is involved from controller to the display?

jason · Post by **jason** » Thu Mar 31, 2005 12:33 pm

Miles,

I would say it's about 6 to 8 inches from the controller to the display.

Miles · Post by **Miles** » Thu Mar 31, 2005 1:08 pm

Is the lock up random or does it appear within a specific time frame?

jason · Post by **jason** » Thu Mar 31, 2005 1:10 pm

It locks up random....anywhere from 2 minutes to at least 1 hour.

Miles · Post by **Miles** » Thu Mar 31, 2005 1:15 pm

What type of cable are you using to connect your controller with the displays?

jason · Post by **jason** » Thu Mar 31, 2005 1:38 pm

I'm using a 4 pin ribbon connector, in which the whole package and wiring is done within a grounded sealed metal box.

Miles · Post by **Miles** » Thu Mar 31, 2005 1:51 pm

Is the display's bezel contacting the metal enclosure??

jason · Post by **jason** » Thu Mar 31, 2005 1:57 pm

Yes it is.

I also have a ground wire attached to the screw that mounts the display to the enclosure.

Miles · Post by **Miles** » Thu Mar 31, 2005 2:04 pm

Sounds perfect!! What type of pull up resistors are you using for SCL and SDA??

jason · Post by **jason** » Fri Apr 01, 2005 7:36 am

Miles,

We have 10k ohm 1/4watt pull-up resistors on SCL and SDA.

I was wondering if it could be noise on the power line or a drop in voltage?

Miles · Post by **Miles** » Fri Apr 01, 2005 7:43 am

A significant drop in voltage may cause a lose of communication...Depending on the hardware involved, I have seen instances were 2.5 Volts on the SCL line will cause havoc, however in other causes it works fine...

Have you played with resistor values...strengthen or weaken the pull ups will affect communication...

jason · Post by **jason** » Fri Apr 01, 2005 7:46 am

No I have not changed the Resistor Values.

Do you think it could be a Power issue?

Miles · Post by **Miles** » Fri Apr 01, 2005 7:56 am

It is very possible...do you have a way to monitor this...?

jason · Post by **jason** » Fri Apr 01, 2005 8:09 am

Yes,

I've got a scope that I can look at the voltage on.