v3.6 and 4x20 LCD issue

[Takumi]

Hello,

just build up the board, tested, uploaded FW - everything seems ok, working ( sopn will be put to the car). Together i bought 4x20 green LCD. Made connection to the board as wiki states: http://www.vems.hu/wiki/index.php?page=GenBoard%2FBuildProcedures%2FLCDconnect and http://www.vems.hu/wiki/index.php?page=MembersPage%2FPeterJensenDisplay . When powered VEMS, lcd screen lights green, but nothing shown... tried different FW with LCD option, just nothing happnes...sometimes backlight begins to flicker ( always just after FW being uploaded) ... Double checked connections, tried to get some more info, maybe there is something more to do? Tried in VEMStune to adjust something for LCD, nothing happens... Any ideas? 

P.S. whole unit is powered on my desk via 12VDC power supply with 1250mA. Can low power source cause this?
Photo:


Thanks,
T.

[Sprocket]

Have you used the correct resistor values for the contrast and backlight?

I had to change the value of the contrast resistor for the larger display I have, but the standard values should work on the shop display. its probibly better to use variale resitors anyway on the contrast, the 27ohm backlight resistor seems to work on either display

http://195.159.109.134/vemsuk/forum/index.php/topic,315.0.html

[Takumi]

Well, tried it - if you would look more to the photo, you can see, that top row andr 3rd row are darker - if i change contrast resistors, i see them as black blocks, no any text, nothing... Can it be because of FW? tied 1.1.63 and 1.1.47 ( with LCD option ) - nothing changed, no any response in Vemstune adjustment...somehow want to think, that LCD controler on board is defective 

[gunni]

Have you wired it correctly?

It needs to be 100% otherwise nothing shows up.

[Takumi]

Have you wired it correctly?

It needs to be 100% otherwise nothing shows up.

10x checked with tester, re-soldered... same story :|
BTW, as mention url before, i used to wire it up, maybe there are some changes for v3.6 and LCD wiring?

[Sprocket]

Its not the firmware, its something with the hardware.

My LCD is wired as per the Wiki table and works fine, so it has to be wiring error or a faulty LCD.

Fit a Ferite core on the cable and ground the screen(drain) wire on the cable.

Have you wired it by colour or by Dsub9 pin numbers? as some serial cables have different colour scheduling, as I found out back in 2007.

You could also do with a little more solder on the LCD pads

[Takumi]

tried rewire again, used shielded cable, soldered more, checked from board if signal is - everything is 101% connected correctly... This is what it shows, if backlight is disconnected:


Could it be, that 74HC243D chip is faulty? It's located under the board, near LCD conncting pins, think it is responsible for LCD control... Dont know anything more to blame 

[mattias]

I have to concur, this is all in the wiring or  damaged electronics  due to wiring error but that rarely happens.