[Guide] ili9341 SPI TFT Screen on Retropie

[moosepr]

Hi Folks,



I know SPI screens get a bad write up, they are not as fast, they suffer with 'tearing' and they use up your gpio pins, but they have lots of benefits too!

You can get a screen that is ready to roll with no modifying for somewhere in the region of $6, they come in a range of sizes (2.2",2.4",2.8") and you can chop away excess PCB and get it rather small. They have a few more wires, and some slight software tweaks are needed to get them to work. So first off, lets get the wires connected.

Display--------Raspberry Pi
BL--------------pin 12 (GPIO 18)
SCK------------pin 23 (GPIO 11)
MISO----------pin 21 (GPIO 9)
MOSI----------pin 19 (GPIO 10)
CS--------------pin 24 (GPIO 8)
RST------------pin 22 (GPIO 25)
D/C-------------pin 18 (GPIO 24)
VIN-------------pin 17 (3.3v)
GND-----------pin 20 (GND)

So now your pi is wired up, get your pi up and running with a keyboard and a screen, we need to start to get things working. I am assuming we are working on a fresh install of RetroPie

First off we need to change a few "system" settings on the pi. If you exit emulationstation and in the terminal type

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sudo raspi-config

you will be presented with a blue screen and some options. in the advanced options you want to make sure overscan is disabled, and spi is enabled. use the arrow keys to select 'finish' and when prompted, reboot

once you are back up and running again, exit emulationstation once more and get yourself back to a terminal and type

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sudo modprobe fbtft_device custom name=fb_ili9341  gpios=reset:25,dc:24,led:18 speed=16000000 bgr=1

the backlight should kick in on your tft screen. This is a good sign!!

now try typing

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con2fbmap 1 1

your console should now be on your tft screen!!


hurrahh

you can always type

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con2fbmap 1 0

to get the console back onto your normal screen. Go make your self a drink, you are halfway there!!

OK, so we have proven the screen works, we need to make things more interesting. Firstly, you might have noticed that if you were to restart the pi, you will need to type your modprobe line in again to restart the screen. now this is no fun for a tiny handheld, so lets make the screen work every time.

First off we need to tell the pi to load the screen module at startup. We can do this by editing a file. type this,

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sudo nano /etc/modules

this will fire up the text editor nano, with the modules file, so we can add in the bits we need. Add in the following 2 lines, below what is already there.

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spi-bcm2835
fbtft_device

Press ctrl+o to save (press enter to confirm file name) and press ctrl+x to close the text editor

You need to add the spi line, so that we are sure the connection port is ready for use, and then the tft device starts the screen. but we need to add in all of those extra settings that we had to type before. there is a place for this and it is another file. type this

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sudo nano /etc/modprobe.d/fbtft.conf

and inside the text editor, we neeed to add the following information (the file will probably be empty)

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options fbtft_device name=fb_ili9341 gpios=reset:25,dc:24,led:18 speed=16000000 bgr=1 rotate=90 custom=1

Again we need to press ctrl+o to save (press enter to confirm file name) and press ctrl+x to close the text editor

now try restarting the pi (I normally type sudo init 6) and let the pi restart. Fingers crossed your screen will light during the reboot process. If not, check your files for typo's, and check dmesg for any errors.

If your screen is illuminated, you can check it is ready to roll with the good old

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con2fbmap 1 1

to check you have the console there on the screen. Now the screen is working on every boot, we can make it do more things....

So the screen works, and it loads every time, we now just need to make it do something fun. The main sticking point with these screens is that there is no real 'graphics acceleration' we can use with them. The only way it will work is to install some software to basically copy the current screen over to the ili9341 screen. now this is quite a simple task, we just need to type the following in a fresh terminal

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sudo apt-get install cmake
git clone https://github.com/tasanakorn/rpi-fbcp
cd rpi-fbcp/
mkdir build
cd build/
cmake ..
make
sudo install fbcp /usr/local/bin/fbcp

this will install the software to copy the contents of the screen over to the tft. We now need to test this, you want to type

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fbcp

and if all has gone well, the contents of your normal screen will appear on your ili9341 screen!!! hurrah!! i think its time to grab yourself a beer!!!



we just need to make this happen every time we boot. This is actually simple to do. We just need to add our newly installed program into the pi's autostart config file. To do this, we need to fire up the terminal again

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sudo nano /etc/rc.local

within this file you will see there is already some text in there. You need to make an addition between the ip address code and the exit line. You need to add in the line

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fbcp&

the ampersand (&) needs to be there to make sure our fbcp program runs in the background. our file will now look something like

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_IP=$(hostname -I) || true
if [ "$_IP" ]; then
  printf "My IP address is %s\n" "$_IP"
fi

fbcp&

exit 0

there may be some comments up above, but these are just there for information. If you restart the pi now, you will see the screen initialise, and then it should show the splash screen after a few seconds. before you know it, you will have your pi up and rolling on the tft screen!! Top job!!!

[Mischief]

Nice guide, but some of your images are not showing.

[moosepr]

Nice guide, but some of your images are not showing.

That's a pain! The images are not really critical to the guide, but I will get them shifted

edit : i have moved the images to imgur now, should behave better

[kamon]

Thanks for the info!


Looking to put one of these(the 2.8" version) to use in a GBA build.
Do you know where exactly I can chop the PCB to cut down the size of it?

Maybe a picture with some black lines to get an idea?

Thank you!

[moosepr]

Thanks for the info!


Looking to put one of these(the 2.8" version) to use in a GBA build.
Do you know where exactly I can chop the PCB to cut down the size of it?

Maybe a picture with some black lines to get an idea?

Thank you!

Basically you can prise up the screen, they are stuck down with double sided tape. Then you will be presented with this



The screen is now covering the pins (there is no getting away from those I'm afraid) but pretty much anything to the right of the ribbon cable should be able to be scrapped. You might need to check the other side of the board, the only one I have is stuck down.

You can see the traces really well on these boards, so they are easy to check. Each of the pins will go to one of the 18 pins in the ribbon cable. 18-15 are for touch 14-10 are for the backlight 9-1 power and control the screen (this should help you trace the pins)

[Helder]

Nice! I was looking into testing some of these screens, so in the initial start of the guide you have the Pi connected to an HDMI monitor?

[moosepr]

Nice! I was looking into testing some of these screens, so in the initial start of the guide you have the Pi connected to an HDMI monitor?

Yeah I started with an Motorola atrix lapdock (screen and keyboard in a laptop form factor with USB and HDMI) you can in theory use it as a second screen displaying box art or system status.

I have been playing with getting away from the oversized PCB, the ribbon pretty much has raw SPI pins



I just have a resistor for backlight brightness control to keep things really simple, but it works!

[Helder]

Nice! I was looking into testing some of these screens, so in the initial start of the guide you have the Pi connected to an HDMI monitor?

Yeah I started with an Motorola atrix lapdock (screen and keyboard in a laptop form factor with USB and HDMI) you can in theory use it as a second screen displaying box art or system status.

I have been playing with getting away from the oversized PCB, the ribbon pretty much has raw SPI pins



I just have a resistor for backlight brightness control to keep things really simple, but it works!

Nice! I was looking into finding the simplest screen with the least amount of pins on the ribbon. I don't want to bother with 40 or 50 pins when only a handful are used.

Do you have any recommendations? also do you need anything else to make these screens work? I'm trying to find schematics of those boards that come with the screens but there seem to be many variants of the same thing. Do you use a voltage regulator for the screen and backlight?

[moosepr]

Do you have any recommendations? also do you need anything else to make these screens work? I'm trying to find schematics of those boards that come with the screens but there seem to be many variants of the same thing. Do you use a voltage regulator for the screen and backlight?

These are the only ones I have tried, all the others seem to have lots of pins.

The screen seems to run well on 3.3v, so I'm just powering it from the Pi's 3.3v pin with no issues. Just added a resistor for the backlight, but it does work straight to 3.3v too!

I couldn't find a schematic for the boards, just a pinout http://s.aliexpress.com/JvYJvAre, so I risked the $2 on my test boards. The 2.4 and 2.8 screens have an extra 4 pins for touch

I have a board where the screen ribbon goes straight to the pi gpio with no other components, I'm just waiting on China Post for some naked screens to test it with (been 4 weeks already )

[kamon]

Thank you!!! Ordered one to play with .

Also, guys.
I followed a project awhile back where someone built a custom PCB for the GBA and used a 3.2" SPI LCD, here's a link to the GH project:

https://github.com/Ryzee119/GBA_Emulator-by-Ryzee119-/

Not only did they release their Eagle files so you can get the boards made, but they also had a SPI breakout board over on oshpark: https://oshpark.com/shared_projects/9tH3I87q

Looks like everything would work.

And, even more interesting to me:
@Helder, would you ever be interested in turning his Eagle files into a more robust one that at least has X/Y buttons, and preferably with some of the features your AIO has?

Maybe even for commission ?