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Topic: how to use 4 inch raw tft lcd and replace it with 2.4 inch on module ? (Read 438 times) previous topic - next topic

marteen1337

Hello every one ...

i have a question about replacing 2.4" tft lcd with larger size 4" on the 2.4" shileds
so if i buy the 4" lcd with 8/16bit parallel interface and with 37pins or 40pins on lcd ribon cable,
is it possible to replace it with 2.4" lcd on module PCBs?
(the modules PCB have 2 ICs, is it working with larger size of tft lcd?)

i have the image of these 4" lcds:
ST7796s supports SPI and Parallel (named on picture)
ILI9486L supports only Parallel

and next question which is better for Parallel mode? (ST or ILI)

thanks !


david_prentice

It depends on your 2.4 inch pcb.
If it has an AMS1117-3.3 regulator
If the ribbon matches a footprint on the pcb.
The pcb will be smaller than the screen.

It is much wiser to buy a ST7796S shield that will just plug into Uno and work e.g. this ST7796S Shield

Note that it has :
R1 to limit the backlight current
U1 AMS1117 3.3V regulator
U2, U3 74LVC245 buffers.

Most modern "mcufriend" shield pcbs are WRONG.
Some Blue shields that look like my link have different components.

David.

marteen1337

thanks again ...

so the pin order(numbering) on the 4" and 2.4" is same ! or not ?
and buffer ics can works with 4" ! its good

ili9486l have a different ribbon (pad pitchs is higher , 0.8mm i think)

actually at this time the shops havnt  shield in my country so i had to test with this way :smiley-confuse:

david_prentice

You need the correct pitch and the same ribbon pinout.

Red Mcufriend pcbs vary.   Most have a choice of ribbon footprint.   But there is no point in trying to do anything if the ribbon does not fit.

Buffer ics must be correct if you use a 5V Uno or Mega.  74HC245 are WRONG chip.   74HC245 is not input voltage tolerant.

David.

marteen1337

SM245TS is another buffer ic and its works good

yes im using 3.3 volt from regulator AMS1117 or using 3.3v from arduino boards

if i use 3.3v supply both buffer ics is good for 4" lcd or not ?
so why  74hc245 is wrong ? my 2.4" shield works fine with it?

marteen1337

can use this shield only for 8-bit parallel ?

product info:
Size: 3.5 inch
Control chip:ILI9486L
Touch control chip: XPT2046
Resolution: 320*480
Display area: 48.96 x73.44 (mm)
Physical size: 57.26  * 96.5
Interface Type: 16Bits parallel interface
Number of pins: 34Pin
Display color: full color
Pixel size: 0.153 x 0.153(mm)
temperature: -20~70  °c
voltage: 3.3V

the image uploaded ...



david_prentice

SM245TS seems to be a Chinese 74HC245 but I can not find a proper datasheet for SM245TS.

You should NOT take more than 50mA from the 3.3V pin on a Uno or Mega2560.
But Zero and Due can supply up to 500mA from their 3.3V pins.

Measure the 3.3V pin on your Uno / Mega when the display is working.

Please provide a proper link to your ILI9486L display.
I can not identify the components on the pcb.
So I can't tell you whether it can be configured for 8-bit Parallel

David.

marteen1337

okay !
im upload SM245TS datasheet and this lcd shipping link here:


https://kavirelectronic.ir/eshop/tft-lcd-40-inch/1201035-4inch-lcd-display-module-with-touch-320x480-hd-parallel-ili9486l.html

https://kavirelectronic.ir/eshop/tft-lcd-35-inch/1201032-%D9%85%D8%A7%DA%98%D9%88%D9%84-35-%D8%A7%DB%8C%D9%86%DA%86-%D8%A8%D8%A7-%D8%AA%D8%A7%DA%86-35inch-lcd-display-module-with-touch-320x480-hd-parallel-ili9486l.html

(mega2560 is expensive for me - so i want to use this parallel lcds with 8-bit mode and mega32
these are designed with D0~D15 pins on pcb module, i dont know its possible to use only D0~D8 for using this modules ?)
(more info for this 2 links: the ic on pcb modules is XPT2046 , not a buffer ic)

david_prentice

Thanks for the Chinese datasheet.   Google Translate says:
Quote
Logic input voltage VI1 -0.5 ~ VDD + 0.5 V
So it looks as if it is a regular 74HC245.   i.e. only input voltage tolerant for VDD + 0.5V
Your 5V Uno, Mega2560 will have 5V logic signals.   The buffer chip's VDD is supplied from the Arduino 3.3V pin.

So the 74HC245 substrate diodes will conduct whenever a control or data bus signal is high.
All of the 8080-8 interface control signals are Quiescent High.

Did you measure the 3.3V pin on your Arduino ?
Mcufriend pcb design is criminal.

It looks as if the 4.0 inch and 3.5 inch screens have the same pcb layout and 34-pin header.
It looks as if R13 is unmounted.   This might be access to 8080-8 versus 8080-16 selection.

Without the pcb on my desk I do not know what the pcb schematic might be.

I strongly advise buying standard display / adapter shields.   It lets you get a prototype working.
And then you can copy their schematic / pcb layout for any custom pcb for your product.

David.

marteen1337


Quote
Did you measure the 3.3V pin on your Arduino ?
no problem with 3.3v current/voltage ! works good with shields!

Quote
Mcufriend pcb design is criminal.
no im not copy the mcufriends shields, i need to show a test for my customer on large size lcd
and have enough money to buy new module :smiley-confuse:  , im just need one sample with 4" and then they buys
shields and send it for completing projects 

there is no R13 on this 4" / 3.5" shields (i havnt this lcds at this time)

what is buffer ics do in the shileds? they convert 16-bit to 8-bit?
i think if shields havent buffer, we can only use in 16-bit mode? is it true?


thanks ...

david_prentice

no problem with 3.3v current/voltage ! works good with shields!
I don't believe you.   If you have 74HC245 you will see 3.8V - 4.2V when you use a 5V Uno or Mega

Quote
no im not copy the mcufriends shields, i need to show a test for my customer on large size lcd
and have enough money to buy new module :smiley-confuse:  , im just need one sample with 4" and then they buys
shields and send it for completing projects
You can not trust your customer to wire 34-pin displays.

Quote
there is no R13 on this 4" / 3.5" shields (i havnt this lcds at this time)
An Uno does not have enough pins for 8080-16 interface.

Quote
what is buffer ics do in the shileds? they convert 16-bit to 8-bit?
No.   The buffers convert the 5V logic from the Arduino to the 3.3V signals needed by the TFT module.
If you have a 3.3V Due,  you do not need buffers.   (but they do no harm)

Quote
i think if shields havent buffer, we can only use in 16-bit mode? is it true?
No,  R13 might select 8080-8 interface.   In which case you need less Arduino pins for 8-bit mode.    But you still have to convert signals to 3.3V i.e. level converters but it is a smaller number of level converters.

David.

marteen1337



Quote
I don't believe you.   If you have 74HC245 you will see 3.8V - 4.2V when you use a 5V Uno or Mega
i should check with other DMM !


thanks !

marteen1337

hello !

thanks for your advice to buying shields !
i remove my old 2.4" tft lcd from pcb there is no 37pin and 40 pin soldering pads
there just a 24pin and 31pin pads for lcds that have 1mm pitch for pads

so there is no parallel module in IRAN for shiping and i have another questions:
1- is possible to use the logic level converter for raw tft lcd 4" (im upload some logic converters pics here)
2-i need schematics for connecting two 74HC245 to my 4" raw lcd (do you have a corrected sch?)







david_prentice

Seriously.   If you want to use a bare 3.3V module,   connect directly to a 3.3V Due.   Either in 8080-8 or 8080-16 mode.

If you want to use 5V Uno or Mega2560 use a proper Arduino Shield.

I would use 74LVC245 buffers instead of TSX0108E.
Either way it is much more work than using a proper 3.3V Arduino.

David.

marteen1337

unfortunatly there is no 8-bit lcd in Iranian market at this time!
and we cant buy shield from other countries

https://www.aliexpress.com/item/4000127049804.html
this link is filtered in iran - im open it with vpn :(



i cant use DUE board because of its expensive for production in large quantity ! (and also mega2560)



my project is in the edge of cancelling beacuse of no 8-bit lcd found here:smiley-confuse: i need to talk for get more time ...


thanks a lot ...

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