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LCD20x4 freezes


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Hey folks,


I'm having trouble with my LCD20x4 after upgrading the master brick firmware to the latest version today.

After a certain amount of time the backlight is somehow disabled, and the LCD no longer responds to any commands send from brickv or my Java program. The buttons are still functional thought! I can see brickv reporting "pressed" and "released" when i press the 3 buttons.

There are no errors reported by either brickv or the running Java program.

When i look closely to the LCD I can still see the text that it was showing last, altough its hard so see with the backlight off.


The master brick (1.1) is running version 1.2.4 of its firmware, and the LCD bricklet has firmware version 1.1.0.


3 other bricklets connected to the same master brick still function like they should, so it looks like an isolated LCD problem. When I hit the reset button in brickv the master brick restarts and the LCD work again, only to freeze again after a seemingly random period of time.


I hope this description is informative enough to locate the problem. I'm trying to create a reproducible scenario that triggers the problem.


Kind regards,

Geert Schuring.

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I just witnessed the backlight switching off for the first time. On previous occasions it always switched off when I was not near the LCD, so I assumed it 'switched' off.

Now it turns out it slowly fades out... It takes about 20 seconds from my first thought "hey that backlight used to be brighter" to it being completely dark.


Conclusion: It doesn't switch off, it somehow looses power or something like that and after the screen stops responding to commands, the backlight slowly fades off.

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Before you update the Master Brick firmware this problem wasn't there?


What are the other Bricklets on the Master, is there a Dual Relay on there too?


Its hard to say whether this problem existed before because i've never used the LCD as intensive before today. Coincidentally, i've also updated the master bricks firmware today.


There is indeed a DualRelay bricklet attached to the same master brick, but there isn't anything attached to it. I must admit though, that i've been testing the response time by making it perform flops with only 10 ms delay, or lower. I now recall having seen the LCD dimm slightly while the DR was switching.


I'll try removing the DR from the setup and test the LCD some more. I have not been able to come up with a reproducable scenario so far. Last time the LCD run perfectly for hours while receiving an update at least every second. (showing a clock and temperature readings)

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That the LCD dimm slightly when switching the DR is normal.

The reason is, that the DR draws a significant current when switched on, so the voltage drop across the protection diode on the bricks is higher. This leads to a lower voltage on the 5V line and a slightly darker LCD backlight.


Regarding the LCD Problem. Please write us an email, there seems to be something wrong with it.

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