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Glen0
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Posted: 09:11pm 27 Jan 2022

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I have just received some LCD screens through Aliexpress and I cannot get them to work. The screen lights up when the Pico is powererd up and there is a very brief scrambling of black lines and then it reverts to a white screen.
I have tried connecting as per the Picomite manual as well as the Silicon chip article but no go.

I am trying to get it working as a display only first and once that is working I will try my hand at touch and SD. That brings me to another point, the website says this LCD is "no touch" yet it looks suspiciously like it has that option. Can anyone confirm this from the pictures which I hope have uploaded successfuly?

This is the description of the display on the website, "SPI module 14 pin 3.2 inch 18P ILI9341 TFT LCD colorful screen 4 wire Serial port 320x240 No touch panel adapter PCB board"

Edited 2022-01-28 07:15 by Glen0

phil99

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Posted: 09:31pm 27 Jan 2022

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The board appears to have the touch chip fitted, but to see if the touch foil is also fitted look at the top side, connector end there will be a four way flexible PCB strip running from the top of the panel and down under it.

lizby
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Posted: 09:43pm 27 Jan 2022

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Don't know that it would make a difference, but MISO appears not to be connected.

Also, although the Picomite manual shows GP20 as a MISO pin, the PICO pinout image that I have followed doesn't.

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hitsware2

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Posted: 09:53pm 27 Jan 2022

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lizby said Don't know that it would make a difference, but MISO appears not to be connected.

Also, although the Picomite manual shows GP20 as a MISO pin, the PICO pinout image that I have followed doesn't.

As I understand , MISO is not used with displays ....
It would be transmit from the display ( doesn't happen )

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disco4now

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Posted: 09:56pm 27 Jan 2022

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When powering from 3.3v you should bridge J1 which bypasses the regulator. Normally seems to work without doing this, but should be done to ensure you are getting 3.3v

It seems to have the touch chip, if on the screen side you can see a separate 4 wire ribbon going to the top layer of the screen then it likely to have touch.

You can use the PIXEL command and function to see if the screen is talking to you even if it has not initialised properly.

PIXEL 0,0,RGB(RED) to set a pixel at 0,0.
then
? HEX$(pixel(0,0)) to read it. Returns FC0000 for red if it works.

(You need MISO connected to read the pixel. Is your white wire going somewhere we can see?)
Edited 2022-01-28 08:01 by disco4now

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palcal

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Posted: 10:11pm 27 Jan 2022

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In the TEXT line you have "CM" I think it should just be CM no inverted commas.

"It is better to be ignorant and ask a stupid question than to be plain Stupid and not ask at all"

lizby
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Posted: 10:41pm 27 Jan 2022

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hitsware2 said

As I understand , MISO is not used with displays ....
It would be transmit from the display ( doesn't happen )

As I understand, MISO is used for BLIT READ (but isn't needed if you only write to the display--thus "Don't know that it would make a difference").

PicoMite, Armmite F4, SensorKits, MMBasic Hardware, Games, etc. on fruitoftheshed

palcal

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Posted: 10:47pm 27 Jan 2022

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I have never used the "" with the alignment but apparently it works either way.
Edited 2022-01-28 08:53 by palcal

"It is better to be ignorant and ask a stupid question than to be plain Stupid and not ask at all"

Glen0
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Posted: 02:02am 28 Jan 2022

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Thanks for all the help.
I hope the following responds to all the contributions:

I checked the front of the screen and it does have the the Touch 4-conductor ribbon to the top.
I am powering from VBUS, so it's 5V. I also tried using an externally powered USB hub.
MISO not connected. (as per Silicon Chip mag)
Tried the Pixel command and it returned FFFFFF
Removed the inverted commas from both CM's and no change

Is there maybe something I am doing wrong with MM Edit
Do I need to have the Touch terminals connected?

TassyJim

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Posted: 03:00am 28 Jan 2022

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It's nothing to do with MMEdit

Try
GUI TEST LCDPANEL
That tests the display without having to worry about programming issues.

Jim

VK7JH
MMedit MMBasic Help

disco4now

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Posted: 03:04am 28 Jan 2022

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You don't need touch connected, but if you do connect T-DO, T-DI, T-CLK you must ensure T_CS is high to ensure the touch does not interfere with the SPI. OPTION TOUCH will pull T_CS high. Leave them unconnected until you get screen going.

Have you tried
GUI TEST LCDPANEL
at command line. This will send a stream of circles of different colours to the screen.

The PIXEL read will only work with MISO connected. Could be worth trying, if it reads successfully you have proved SPI is OK and the issue is initialising the LCDPANEL.

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hitsware2

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Posted: 03:26am 28 Jan 2022

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lizby said

hitsware2 said

As I understand , MISO is not used with displays ....
It would be transmit from the display ( doesn't happen )

As I understand, MISO is used for BLIT READ (but isn't needed if you only write to the display--thus "Don't know that it would make a difference").

I see now that some displays ( maybe most ?) ( but not the one I have )
have a MISO pin .

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disco4now

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Posted: 03:53am 28 Jan 2022

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Try these new POKE commands to see if they do anything. Again will prove the SPI if they turn screen on/off

POKE DISPLAY &H28
POKE DISPLAY &H29

Also these in case the colours are inverted, e.g. black is white
POKE DISPLAY &H20
POKE DISPLAY %H21

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Glen0
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Posted: 03:36am 02 Feb 2022

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Thanks I tried all the actions recommended but no luck.
I later noticed a solder jumper on the board "J1" and bridged it out with a little solder and now for a very brief time when powering on it displays the date and time as per the program but then it goes blank again. Progress I suppose.
Any ideas?

Glen0
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Posted: 03:47am 02 Feb 2022

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The jumper brides out 2 of 3 pins on a small smd component, "U1", which is a "662K"
If I am correct this is a voltage regulator and it bridges the in and out pins.
Edited 2022-02-02 13:49 by Glen0

phil99

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Posted: 04:41am 02 Feb 2022

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"If I am correct this is a voltage regulator and it bridges the in and out pins."

Yes it does, if powering from 5V that will damage any 3.3V item attached such as SD card and PicoMite.
Only bridge J1 if using 3.3V. Most use 5V with J1 open.

Bill.b

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Joined: 25/06/2011
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Posts: 225

Posted: 05:50am 02 Feb 2022

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Have set up the LCD panel at the command prompt.
From the manual Page 48 :-

"To match the above connections the following configuration commands should be entered, one by one at the
command prompt:
OPTION SYSTEM SPI GP18, GP19, GP16
OPTION SDCARD GP22
OPTION LCDPANEL ILI9341, L, GP15, GP14, GP13
OPTION TOUCH GP12, GP11"

Bill

In the interests of the environment, this post has been constructed entirely from recycled electrons.

Glen0
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Posted: 06:19am 02 Feb 2022

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I think the Pico has survived despite the 5V, luckily.
Does the fact that soldering the jumper gives a brief correct display at power-up, help in pointing out where the problem is?

I have been following the manual to the letter, hopefully and all options entered accordingly.
Thanks

phil99

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Posted: 06:51am 02 Feb 2022

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To see if that regulator is working measure the voltage on both pads of J1. There should be 5V on one and 3.3V on the other. The metal case of the SD socket is a good ground point.
Running out of ideas.

Mixtel90

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Posted: 07:45am 02 Feb 2022

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Is the backlight lit? Try a 100R resistor from the LED pin to 3V3. Failing that, try it to GND instead. I don't think I have a circuit for the 3.2" display.

Some of the displays use a simple resistor to set the brightness but Q1 isn't fitted. Where Q1 is fitted the backlight is powered via that and you can connect the LED pin to a PWM output to dim the display.
Edited 2022-02-02 17:49 by Mixtel90

Mick

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