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Forum Index : Microcontroller and PC projects : ILI9488 MISO Fault Question

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matherp
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Joined: 11/12/2012
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Posts: 6619
Posted: 10:38am 30 Nov 2022
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When trying the 680R resistor are you putting it in the right place? It should be between the display MISO (SDO) pin and the Pico. It should not be anywhere near the other MISO (TDO, SDcard SDO),connections to the Pico which should all be direct.
 
stanleyella

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Joined: 25/06/2022
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Posted: 09:35pm 30 Nov 2022
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@phil "Are you certain all the breadboard connections are perfect? No one else is having this much trouble."
I will vero it. breadboard for this IS lots of wires and although the circuit is the same the results are different.
It seems this display is annoying compared to ili9341 from all the ways to get it working so not just me.
I would rather use ili that works than this hit or miss device.
I will keep trying but think I am flogging a dead horse.
thank you for the advice everyone.
cinders, you will go to the ball... not
 
phil99

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Joined: 11/02/2018
Location: Australia
Posts: 756
Posted: 10:53pm 30 Nov 2022
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"It seems this display is annoying compared to ili9341 from all the ways to get it working so not just me"

I think you have got the wrong idea. That there are so many ways to overcome the issue shows that it is easy to fix.

Everyone finds that just adding one 680R resistor fixes touch and for most it also fixes SD access.

Get touch working first with the 680R and then test SD. If SD won't go or is unreliable try any of the other fixes. I have tested them all and they all work on my ILI9488.

Repeating what Peter just wrote, The ONLY thing connected to SDO (in your photo its SDO(MISO)) is the 680R. T_DO and SD_DO go directly to the Pico MISO pin GP16.



This is a simple way to eliminate the possibility of connection problems.
Edited 2022-12-01 17:33 by phil99
 
DrifterNL

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Joined: 27/09/2018
Location: Netherlands
Posts: 19
Posted: 07:24pm 01 Dec 2022
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This is how I got the ILI9488 LCD working:


 
stanleyella

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Joined: 25/06/2022
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Posted: 07:39pm 02 Dec 2022
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  phil99 said  "It seems this display is annoying compared to ili9341 from all the ways to get it working so not just me"

I think you have got the wrong idea. That there are so many ways to overcome the issue shows that it is easy to fix.

Everyone finds that just adding one 680R resistor fixes touch and for most it also fixes SD access.

Get touch working first with the 680R and then test SD. If SD won't go or is unreliable try any of the other fixes. I have tested them all and they all work on my ILI9488.

Repeating what Peter just wrote, The ONLY thing connected to SDO (in your photo its SDO(MISO)) is the 680R. T_DO and SD_DO go directly to the Pico MISO pin GP16.



This is a simple way to eliminate the possibility of connection problems.


Ta again phil99.
I rewired as before ie 680R from lcd miso to touch t_do and sd_do and it is the same in that it appears to work fine. Touch calibrates and works fine, it reads a sd card and the graphics seem fine.
But then as before I found blit does not work. A test program that moved 16 sprites now moves 16 white squares until the screen is full.
I tried the diode resistor circuit with same results.
Just the p200 transistor circuit to try but I have none so I'll check if I got an equivalent.

If it was not for blit failing I would have thought the 680R in lcd miso a simple solution
and who uses blit on lcd anyway?
 
phil99

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Posts: 756
Posted: 08:37pm 02 Dec 2022
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The only thing that can prevent BLIT working is too high a resistance between SDO and Pico MISO. Perhaps your resistor has the wrong markings on it.
With the power off measure the resistance between the SDO(MISO) pin on the panel and MISO (GP16) on the Pico.
I have tried a variable resistor instead of the 680R, above 1k the number of Blit colours decreases until there is just one - white.
If the resistance is decreased SD and touch stop working.
Edited 2022-12-03 06:38 by phil99
 
stanleyella

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Posted: 10:10pm 02 Dec 2022
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  DrifterNL said  This is how I got the ILI9488 LCD working:




Hi DrifterNL. Have you got blit working? What others think sorted is not.
The solutions get touch and sd card to work and coloured filled circles
so assume all is ok, when it is not.
I found option reset and setup needed to get lcd back to no 680R and blit working but touch and sd card do not.
The comment "no one has this problem" is just me.
I do not think the display is faulty, except miso problem, so I will find a use for it but do not know if touch and interrupts work yet.
As is, a nice display but compared to ili9341 is too time taking, ili9341 works no prob.
 
stanleyella

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Posted: 10:32pm 02 Dec 2022
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  DrifterNL said  This is how I got the ILI9488 LCD working:




Hi DrifterNL. Have you got blit working? What others think sorted is not.
The solutions get touch and sd card to work and coloured filled circles
so assume all is ok, when it is not.
I found option reset and setup needed to get lcd back to no 680R and blit working but touch and sd card do not.
The comment "no one has this problem" is just me.
I do not think the display is faulty, except miso problem, so I will find a use for it but do not know if touch and interrupts work yet.
As is, a nice display but compared to ili9341 is too time taking, ili9341 works no prob.
2 resistors, about <700R, see if I got 1K pot.
 
stanleyella

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Joined: 25/06/2022
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Posts: 461
Posted: 11:32pm 02 Dec 2022
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  phil99 said  The only thing that can prevent BLIT working is too high a resistance between SDO and Pico MISO. Perhaps your resistor has the wrong markings on it.
With the power off measure the resistance between the SDO(MISO) pin on the panel and MISO (GP16) on the Pico.
I have tried a variable resistor instead of the 680R, above 1k the number of Blit colours decreases until there is just one - white.
If the resistance is decreased SD and touch stop working.

I will try a 1KR pot, who knows. maybe but as display working then draw an interface and test mmbasic trig for analogue displays which I wouldn't use blit for anyway.
I just found this display in a box of bits and wish I hadn't.
 
phil99

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Posts: 756
Posted: 11:57pm 02 Dec 2022
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"With the power off measure the resistance between the SDO(MISO) pin on the panel and MISO (GP16) on the Pico."

What reading do you get with the 680R connected?
Put the probes on the pin on the display and on the Pico pin so that all the connections in between are also being measured.

The two resistors look like 390R, though it's had to be certain, so about 780R total.
The angle of your photo makes it hard to see where all the jumpers go, so I can't see if it is right or not.

My test with the variable resistor showed that 680R is the best value to get both Blit and Touch working together. After you get that far we can sort out the SD card.

"I found option reset and setup needed to get lcd back to no 680R and blit working"

That you need to do that suggests you have a wrong connection somewhere.
I have not had to do that. As long as the power is off when I change things a reset is never needed.
SDO should never be directly connected to T_DO or SD_DO as that will overload the outputs. Could that causing your need to reset?

"no 680R and blit working but touch and sd card do not."

Yes, that is the whole point of adding the extra components.

.
 
DrifterNL

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Joined: 27/09/2018
Location: Netherlands
Posts: 19
Posted: 02:41pm 03 Dec 2022
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  stanleyella said  

Hi DrifterNL. Have you got blit working? What others think sorted is not.
The solutions get touch and sd card to work and coloured filled circles
so assume all is ok, when it is not.
I found option reset and setup needed to get lcd back to no 680R and blit working but touch and sd card do not.
The comment "no one has this problem" is just me.
I do not think the display is faulty, except miso problem, so I will find a use for it but do not know if touch and interrupts work yet.
As is, a nice display but compared to ili9341 is too time taking, ili9341 works no prob.
2 resistors, about <700R, see if I got 1K pot.


Resistor Solution:
I didn't try.

Diode and Resistor Solution:
I tried this and it didn't work for me. I was getting wrong colour values and when I turned the diode around the touch screen stopped working. I didn't do any further tests after that.

Transistor and Resistor Solution:
Click Me
I tried this as well and at first it didn't work.
Only after turning the transistor around, c -> e and e -> c, did it work, as shown here.
BLIT -> works.
Pixel -> works, correct colour values
Touchscreen -> works.
SD card reader -> works.
I am using an SD card adapter module , not the one on the LCD screen.
This is the one I'm using -> SD Card Adapter  
Hope this info helps out some!
Edited 2022-12-04 01:08 by DrifterNL
 
Mixtel90

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Joined: 05/10/2019
Location: United Kingdom
Posts: 3141
Posted: 06:26pm 03 Dec 2022
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Don't be too surprised if you can't get that SD card adapter to work in some situations. It could be marginal at best.
Mick

Zilog Inside! nascom.info for Nascom & Gemini
Preliminary MMBasic docs & my PCB designs
 
stanleyella

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Joined: 25/06/2022
Location: United Kingdom
Posts: 461
Posted: 07:22pm 03 Dec 2022
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This display seems iffy at best. What is wrong with expecting things to work?
Seems silly that ili9488 is being sold if it is faulty.
The circuit I am using and can never find 680R when I want one but did find one...
I am red green colour blind and even wearing glasses could not read colours so meter resistors.
Thanks for others patience and advice.
The existing resistors are 713R.


 
stanleyella

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Joined: 25/06/2022
Location: United Kingdom
Posts: 461
Posted: 12:13am 04 Dec 2022
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673R got blit, touch and sd card read.
Thanks for helping. https://www.youtube.com/watch?v=u79TRias3CM
 
phil99

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Location: Australia
Posts: 756
Posted: 04:50am 04 Dec 2022
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Good news indeed! Persistence wins in the end.

"Seems silly that ili9488 is being sold if it is faulty."

Yes, that is why it is a bit cheaper than other 3.5" displays.
 
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