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Topic: ER-TFTM050-2 5" TFT, how to connect 4-wire SPI without shield to UNO R3 (Read 347 times) previous topic - next topic

SimN

Hello everyone

I am new to this forum and have tried to search for some answers to my problem, but  have found none.

Hopefully somebody with more knowledge of TFTs, shields and SPI can help me.

I have a ER-TFTM050-2 5" TFT with touch screen from EastRising, controller is RA8875. Arduino is an UNO R3, the connection should be 4-wire SPI. With the shield I bought, everything works fine including the touch screen.

However, if I use the shield then none of my I/Os is available anymore. So I tried wiring the display directly with 4-wire SPI according to the datasheets of the display. Nothing whatsoever happens. I have quintuple-checked every wire to every I/O, everything should be fine.

Is there something I am missing or doing wrong when trying to use the display without shield. This should be possible right?

Thanks for any help!

artisticforge

Hello everyone

I am new to this forum and have tried to search for some answers to my problem, but  have found none.

Hopefully somebody with more knowledge of TFTs, shields and SPI can help me.

I have a ER-TFTM050-2 5" TFT with touch screen from EastRising, controller is RA8875. Arduino is an UNO R3, the connection should be 4-wire SPI. With the shield I bought, everything works fine including the touch screen.

However, if I use the shield then none of my I/Os is available anymore. So I tried wiring the display directly with 4-wire SPI according to the datasheets of the display. Nothing whatsoever happens. I have quintuple-checked every wire to every I/O, everything should be fine.

Is there something I am missing or doing wrong when trying to use the display without shield. This should be possible right?

Thanks for any help!
Okay just to be clear.
Are you removing the LCD from the shield?
Are you just removing the shield from the Arduino and connecting the shield to the Arduino with jumper wires?


What is providing power and ground to the display when removed from the shield?
Are the grounds tied together?

Have you asked EsatRising at buydisplay?



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ZinggJM

@SimN

Your first post in this forum is near perfect, congratulation for the clickable link!
Even the information which Arduino you use is available, in the title (where it is easily overlooked).
MEGA uses different pins for SPI, afaik.

The page your link points to has all information needed.
You learn the most if you try to find out yourself.

You will need to tie one or two pins to ground or VCC to tell the controller you use SPI.

Check if the board is made for 5V data signals.
No personal message please; any question may be useful for other users. Use code tags for code. Make links clickable with URL tags. Provide links to the product in question.

SimN

Thanks guys for your replies.

I have of course studied the datasheets available at length.

I tried wiring the shield (attached to display) with jumper wires to the Uno --> nothing (very strange, somehow the cables seem to mess something up)

I tried wiring the display directly via the SPI pins (and VCC 5V + GND of course) to the Uno (according to datasheet of the display) --> nothing
I added the RST and INT pin --> nothing

The board should be made for 5V signals, as J8 is set accordingly on the PCB.

Which pins exactly should I tie to GND or VCC? Why exactly is this neccessary?

Thanks again.


david_prentice

Look at the schematic for your adapter shield.
Does it use level shifter buffer chip(s) ?
What does any LDO regulator chip do?
What do any jumpers or solder-bridges do?

Reproduce exactly the same functionality by hand wiring your external electronics.

BuyDisplay provide all the documentation.   Study it.

They make life easy for Arduino users by providing adapter shields.     Most if not all TFT controllers are 3.3V.    So your GPIO must be shifted from 5V to 3.3V.

Life is simpler with proper 3.3V boards like Zero or Due.   You can wire these directly.

David.

ZinggJM

I took a quick look at the schematics of the shield and the display datasheet.

The shield uses level converters, and the datasheet specifies 3.3V for data lines.
The display board has many solder jumpers; check which interface is selected (page 11 of datasheet).

Unfortunately there is no schematics for the display board; I wanted to check for IM0, IM1.

I did not see an inverter for the RS line on the schematics of the shield; my TFT with RA8875 has RS with inverted polarity.

On the picture of the backside of the TFT I see J9 on, J10 off, so parallel interface may be the default.
No personal message please; any question may be useful for other users. Use code tags for code. Make links clickable with URL tags. Provide links to the product in question.

SimN

Thanks guys for all the help.

Doh... I totally missed the 5V power supply vs. 3.3V logic level matter in the specs.
My bad.

Then of course it won't work with direct wiring without level shifting.

Why it did not work when I connected the shield (all the pins) with jumper wires to the UNO, the same as if it were plugged in, still escapes me...

Zero or Due would be an option. I will consider this.

However the shield, in its 2x20 connector JP1 should have "connectable" SPI ports that run via level shifter, right? (If I read the datasheet and schematic of the shield right).

So technically the following configuration should work:
- shield attached to TFT
- jumper wires from the respective ports in JP1 to the corresponding UNO pins

Should it?

ZinggJM

I did not promise to solve it for you, this is your project.

First check all jumper settings on your display board, any jumper connectors and solder jumpers, on the backside of your display, especially J9 and J10, to find out if it uses SPI or parallel.

The shield is made to be connected to your UNO, and you reported it works when directly connected.

If you connect all pins through jumper wires, and the wires and connections are good, it should still work.

You can then remove the wires you think are not needed, e.g. one by one, to find out which are really needed.

Maybe its faster to study the schematics in detail first, then you learn about the chips used on the shield.
No personal message please; any question may be useful for other users. Use code tags for code. Make links clickable with URL tags. Provide links to the product in question.

SimN

Thanks for all the input ZinggJM.

I finally had some time tonight to fiddle with all the wires and redid the jumper-wire thing except that this time I noticed that the last time I did it, I must have forgotten the ICSP pins at the short end opposite the USB connector.

Turns out the shield uses those pins for the SPI connection. It will not free up D10-13 as the SPI pins are mirrored on the UNO (I just learned), but at least they do not need to be connected.

I will need the shield for the logic level shifting, but now I at least have some GPIO-pins that I can use for some other stuff.

Thanks again for pointing me in the right direction.


ZinggJM

@SimN

Thank you for the feedback. And for the lesson I learn from your post!

I should have noticed from the link in your post, that the same shield is used for UNO, MEGA and DUE.

This can only work with SPI, if the SPI signals are taken from the ICSP connector, as MEGA and DUE use other pins otherwise.

Clever solution from EastRising, and RA8875 is an excellent and performant controller.
No personal message please; any question may be useful for other users. Use code tags for code. Make links clickable with URL tags. Provide links to the product in question.

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