Trouble with 7" LCD

Archive
1

Hi,

The 7" LCD I bought back in October from you for my FEZ Cobra seems to be DOA. Last night was my first attempt at using it, but it just wont power up. I am using an external 6V supply instead of relying on USB power and I did follow the instructions for ensuring the correct cable orientation found here.
http://www.tinyclr.com/downloads/Cobra/Broch_FEZ_7inTFTDisplayKit.pdf

I also followed the LCD Configuration steps, but this too had no effect. I would suspect that I would at least see the backlight power up even if the configuration wasnt done, but I dont see anything that indicates that the unit is getting power. My next step is to pull out my scope and check the corresponding contact points on the flex connector for power. Any other troubleshooting tips would be appreciated.

If it does turn out to be a defective unit, am I SOL, or can it be sent back for repair/replacement?

Thanks,
-Chris

2

Hi Chris,

sorry to hear that. I am betting the team will ask you to email them direct ghielec at ghielectronics.com to work through this. You may find not many people here (the enthusiasts) have forked out for the big 7" display :wink:

good luck and I’m sure the team will help out.

3

GHI tends to be extremely responsive to this kind of stuff. I very, very seriously doubt they will leave you with a broken LCD.

4

I have looked and I can’t find any warranty or return policy information on any of the sites. I know GHI folks do a great job when it comes to customer satisfaction, but I think you need to put something of that sort on the site.

5

The display config work after they are stored then the board is reset.

There is a very thin cable on the display. Does it look broken?

Can you post a picture of how it is connected please?

6

Thanks to all for the quick replies! Gus, I’ll take a pic and post it as soon as I am back at the work bench. Itll be sometime this evening. One question though, even if I messed up the display config, shouldnt I at least see something from the LCDs backlight when it first receives power?

Thanks again,
-Chris

7

This display has all plastic frame so you may not see backlight. I am not sure. I would need to power one up and see how easy it us to see if backlight is on. I will check tomorrow

8

The back light should be on when you connect power whatever the LCD configuration is.

Could you please make sure you connected the cable in the correct orientation. I know this can be confusing sometimes.

Can you also measure the voltage at the backlight cable?

Are you using a powered USB hub or 6Volt external power?you know it is a big display. it sucks power :wink:

9

I measured the voltage at the backlight connection (JP1) and it’s reading 4.7V. I also checked the contact pad of connector X2 on pads 4 and 5 and I read ~4.7 volts. Pads 37 and 38 are ~3.3 volts.

To power it all, I am using an external 6V supply rated at 3.5 amps, so I should have plenty of power.

I doubled checked the connections against your PDF and it looks correct to me.

Thanks again for all the help and here are the pics that Gus asked for.

10

the voltage at JP1 should be about 10 volts. (red wire at +, white at -)

Please contact ghielec at ghielectronics.com for replacement. provide your address and phone number.

11

Hi,
I am too having trouble with the 7" display. It’s backlight is working, and I see colors fullscreen, a checkerboard pattern but no signals from the Cobra.
I have run the LcdConfig code.
The jumper JP1 on the display has 7.9 V on it.

Can you help?
thanks
Peter

12

Did you load the LCD configuration and reset the board for the configuration to take effect?

13

Ok, I got the new LCD and it powers up fine. It initially ran the test patterns on power up and they looked fine. I then ran the LCD config and reset the board afterwards and I now see some GHI boot info and a GHI logo on startup. However…after bootup, the entire screen toggles between two brightness levels about every second.

It only seems to start doing this after the various boot info fields get populated with valid values. Prior to that (and also when it was running the default test patterns), there is no change in the screens overall brightness level.

I also notice a fair amount of flicker when I draw some lines on the screen (all I have drawn so far). I did see from some other posts that the DC supply needs to be very clean, so I checked my supply with my scope and it looks fine.

Any troubleshooting tips would be appreciated.

Thanks,
Chris

14

Try 6v external DC power with 600 to 1000mA.

15

I am using a 6V 3A supply. Should be plenty of current. I also tried a powered USB hub, but the results are the same.

16

Please send an email to ghielec at ghi…
provide your address and phone number for replacement shipping.

17

Joe, you are correct. This was a power supply issue after all. Although the external DC power supply shows up clean on the scope and is rated for up to 3A at 6V, there is something going on with respect to being able to deliver a constant current. Bottom line is that the external supply isn’t any good.

Turns out that if I just run the entire setup off the USB power of my PC, it’s fine. I didn’t even think to try this because my assumption was that my PC’s USB port would have enough current to drive all of it…who knew!

No need for another replacement. All is well now :slight_smile:

Thanks,
-Chris

18

OK, the 7" display is working, I thought I’d reset it but it works now, thanks.

Next step is to configure the MS Visual Studio emulator, so it understands that I have a nice 7" and not the smaller standard displays on a Fez Cobra Windows application. Do you know how to do this?

thanks
Peter

19

The emulator is limited in that sense. One size.

20

Actually, the emulator is limited as is but you can modify the emulator to any size and look you desire. There is an emulator project that ships with Microsoft NETMF SDK