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Malibu
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Joined: 07/07/2018
Location: Australia
Posts: 260

Posted: 11:39pm 31 Jul 2019

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G'day all...

I've had a 5" SSD1963 LCD on the shelf for 12 months and I thought I'll give it a shot (I've been using the ILI9341 previously and successfully)
So, following the example on page 45 of the manual, I've hooked up to a 64E board running 5.05.01 basic.
I couldn't get it to work, so I checked the wiring (many times!) and re-read the words and pictures, but I must be doing something wrong... I'm a bit baffled at the moment.

To cut a long story short, I've narrowed it down to what I think is an LED problem. Right now, it's configured to LED_A control (but I've also tried on board control and 'always on' mode) and without the LED wire connected (to pin 12), I can change the voltage on pin 12 by using the BACKLIGHT (x) command measured on a multimeter, so that's all good.
If I have the backlight at 0%, I can hook up the wire to pin 12 and everything is still running, but of course I can't see anything on the screen.
If I issue a BACKLIGHT 5 (or more %) command, I hear windows lose the USB connection and everything stops working... Gotta disconnect the LED wire, reset windows USB, send a new BACKLIGHT command (blah, blah, blah...)

Here's what I know:
- The test program runs (just a pin cycling hi/low etc) so I know the MM works
- The touch is working because I can get it to register in MM chat (even though the values are wrong because I'm trying to do it 'blind')
- ANY sort of voltage to the backlight will cause the problem, no matter what backlight mode I select.

At the moment, I only have the LCD configured (no touch and no SD) with -
OPTION LCDPANEL SSD1963_5A, LANDSCAPE, 12
(I also tried SSD1963_5 with the same effect)

Two questions for the guru's - Is there something I've missed in configuring and/or is it possibly a faulty LCD?

John

Malibu
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Joined: 07/07/2018
Location: Australia
Posts: 260

Posted: 12:00am 01 Aug 2019

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hmmmmmm...
Just running around the LED pins on the LCD with a multimeter set on diode test...
With black lead on GND and red on LED_A, I get an open circuit. Swap the leads around and I get a reading of 0.685
I don't know what the backlighting setup is on the LCD's, but when I do the same check on one of the ILI displays, I get a reading more like I would expect (similar if I read a normal LED)

John

Grogster

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Joined: 31/12/2012
Location: New Zealand
Posts: 9755

Posted: 02:32am 01 Aug 2019

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You will never be able to run the 5" LCD just from the USB power - the backlight sucks too much juice. The E100 boards get around this issue, by having a DC jack on the other side of the board, for you to plug in a 5v adaptor.

You need the best part of 1A to run a 5" LCD(at 100%), and the USB port generally won't let you have that much, and some USB leads have very poor power wires, and won't pass much current before you get serious voltage-drop anyway.

As you are using an E64-E module, you will need a totally separate 5v regulated power supply, that you hook up to the LCD's 5v input.

If you happen to be trying to run the LCD and/or controller from the E64's 3v3 pin, that won't work either, as the on-board regulator can only supply 250mA in a best-case situation, and there is not enough copper-pour heat-sinking to allow that, so you will quickly overheat the regulator, and it will shut down - this will also cause the USB connection to drop off. This is most likely what is happening as soon as you go from 0% backlight, to 5% backlight - you are probably overloading the on-board 1703 regulator as soon as you switch on the backlight.

The wee SPI LCD's work OK on USB, as they don't suck anywhere as much current for their backlight.

So, what you need is a 5v @ 1A regulated plug-pack to run the LCD, and connect THAT to your LCD's 5v and GND connection. On the 5" LCD's, if you DON'T supply 5v to the 5v pin on the LCD, then the LCD will try to suck the backlight current from the 3v3 supply, and that will quickly overload things with an E64 module, if it is not hooked up correctly.

I will draw a quick diagram and see if I can post it - the forums are still being worked on, so no sure if the images are working yet or not. However, if you put a 5v supply on the LCD, and leave everything else as it is, it should then work.

Let us know how you get on.

Smoke makes things work. When the smoke gets out, it stops!

Malibu
Senior Member

Joined: 07/07/2018
Location: Australia
Posts: 260

Posted: 05:19am 01 Aug 2019

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That nailed it, thanks Grogster!

Sorry, I forgot to mention previously that I already had the 5V supplied from a 5V/3A fixed PSU - not running direct from the USB (I learned that trap a while ago!)
There's no 5V connection on this LCD (as could be the case according to the manual)

My trip up this time was not even giving a thought to the current rating of the 3V3 regulator. A quick rewire and I now have the 5V fixed supply into the MM, plus 3V3 from the variable output on the PSU running just the requirements of the LCD.

It's all good now with a nice screen running a couple of GUI elements on 50%.
Indicated drawn current on the LCD is 370mA @ 50% and 650mA @ 100%

Thanks Grogs, it's very much appreciated!

John

Grogster

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Joined: 31/12/2012
Location: New Zealand
Posts: 9755

Posted: 11:45pm 01 Aug 2019

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Lovely, thanks for letting the forums know.

The E100 board does all that for you, it is only cos you are hooking up an E64 module to an LCD using wires, that you can trip up with that.

Smoke makes things work. When the smoke gets out, it stops!

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