Can you share your lcd screen make/model?
Working SPI Display
Yes, my backlight is on. An excellent question; the device is, in fact, getting proper power.
Yes - the device is a Waveshare 2" SPI LCD display.
https://www.waveshare.com/2inch-lcd-module.htm
I’ve gone over the wiring and conformed it to what you specified. The backlight works, so it’s certainly getting power, and dmesg isn’t reporting any issues like it did last time (with what was apparently a defective Radxa Zero), so I’m stumped.
In waveshare’s documentation page, it says:
RESX: the reset pin, it should be low when powering the module and be higher at other times;
D/CX: data/command control pin, when DC = 0, write command, when DC = 1, write data
Can you play around with the values setting them 1 or 0 in the dts file,
reset-gpios = <0x30 8 1>;
dc-gpios = <0x30 74 0>;
Also make sure you have the correct phandle values of the kernel you are running it from.
Edit:
I can’t really troubleshoot you situation as I dont have exact same lcd screen. (also cost 20$CAD so wont be getting that one). Another way to troubleshoot is really tap on the SPI connection and see if you have some signals coming out, not trying to go deeper and parse out the signal, but may trying to inspect if you have indeed a working framebuffer not a broken display. Otherwise it can be that the display is broken. I used this Signal Analyzer, works great for debugging signals.
Oh, excellent , a way forward! I’ll give this a try!
Considering you haven’t got my hardware, regarding debugging the situation, I think you’re doing an excellent job, and I’m grateful for your help.
Also, if you want I’d gladly buy you this display if you want one.
I’m also strugging to get an LCD display to work. I did a previous topic on loading DT overlays. Now the device-tree processing part is clear, but I still don’t get a /dev/spidev0,0 device file on the system - a plain ArchlinuxArm with a vanilla linux-aarch64 kernel.
I will follow your advice to try and talk to it on the lines.
Other thing I tried recently : boot latest Ubuntu server edition. There I get the spidev1,0 device, but when using it with gpiod as root it fails (see log below). I specially ported a script to gpiod to make sure it works on a Raspberry Pi 4B. I’m using it with a Waveshare 1in44 LCD pHat, so the pins are static.
Traceback (most recent call last):
File "qr.py", line 10, in <module>
from gpiod_lcd import LCD_1in44
File "/home/lafleur/source/radioboite/gpiod_lcd/__init__.py", line 3, in <module>
from gpiod_lcd.LCD import LCD, LCD_1in44, LCD_1in8
File "/home/lafleur/source/radioboite/gpiod_lcd/LCD.py", line 36, in <module>
_raw_screen = LCD_GPIO()
File "/home/lafleur/source/radioboite/gpiod_lcd/LCD_GPIO.py", line 52, in __init__
self.bl_pin = LCD_GPIO._request_pin_out(LCD_BL_PIN, "BL")
File "/home/lafleur/source/radioboite/gpiod_lcd/LCD_GPIO.py", line 75, in _request_pin_out
line.request(config)
File "/usr/local/lib/python3.8/dist-packages/gpiod/libgpiodcxx/__init__.py", line 572, in request
rv = libgpiod.gpiod_line_request(_m_line, conf, default_val)
File "/usr/local/lib/python3.8/dist-packages/gpiod/libgpiod/__init__.py", line 499, in gpiod_line_request
return gpiod_line_request_bulk(bulk, config, [default_val])
File "/usr/local/lib/python3.8/dist-packages/gpiod/libgpiod/__init__.py", line 542, in gpiod_line_request_bulk
return _line_request_values(bulk, config, default_vals)
File "/usr/local/lib/python3.8/dist-packages/gpiod/libgpiod/__init__.py", line 403, in _line_request_values
status = ioctl(fd, GPIO_GET_LINEHANDLE_IOCTL, req)
OSError: [Errno 16] Device or resource busy
I think if you have to work on SPI natively without needing to compile your own device tree overlays or kernel driver, you might need to look at libmraa to interface with spidev. With that you can probably define pin assignments and be able to use python wrappers and use it for your stuff.
I have strong reserves against libmraa because I had erroneous display with the same Waveshare LCD on a RPi4, whereas both RPi.GPIO and libgpiod succeeded (same hardware, same pin assignment). Would you say libmraa has capabilities the two others don’t ?
@mrkprdo In the end I followed your advice and succeeded in piloting my display using libmraa. I’m running Arch Linux and found a working mraa PKGBUILD for Radxa boards on the AUR. I’ll still try to port my script to libgpiod because it feels better integrated in Arch systems ; that will be another story.
As you mentioned, there is no need to compile a specific DT overlay to get SPI display support. I can witness SPI_A works fine using the default overlay. It’s just that the display’s connection instructions I had (written for a RaspberryPi) need to be adapted - specifically, the instructions I had said to use physical pin 22, but this pin is an open drain on the Radxa Zero, which makes it unsuited for input/output as is (followers, see Radxa Zero GPIO specifics).
In the end, what’s unclear to me is when are your LCD driver or SPI display instructions needed - or what benefit they would bring over using the default overlay together with hardware-specific libraries. As @SCIFI.radio mentioned, there would be a need for newcomers’ documentation on this subject. I hope that my questions will help us understanding what happens in a newcomer’s head 
Anyway thank you very much for pointing me in the right direction !
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That’s good to hear you have made it to work.
The SPI display instructions i made is to compile dto with fbtft kernel driver and use the display as framebuffer. End goal is to make these displays as monitor like this.. But unfortunately radxa zero spi is quite slow.
I just debug the st7789vw lcd on my radxa zero，It’s running ok，but there is some issues should be avoided：
- the reset pin on ZERO should be careful of these open drain pins
- It seems difficult to compute or look for the phandler value of the first gpio group,if
U want use these pins as dc or res pins for tft lcds.
3.the ko file should be compiled on you host machine,or the magic problem of linux driver would bother you all times
Hi,
I have a Rock 3c and would like to connect a 2,2" QVGA TFT LCD Display, ILI9341 Driver with SPI.(https://www.elektor.de/2-2-spi-tft-display-module-ili9341-240x320 )
Your guide looks very promising. Did you test it on other Rock’s. What ist the correct configuration of the dto file for ILI9341
Thx
Hey, I think I have had the same setup using the adafruit pi tft spi 240x240 1.3" st7789 display. Mine says that it should be able to work, are you using the same exact display? I am using Ubuntu 20.04. THIS IS THE INSTRUCTION SET TO GET THE RASPI TO WORK WITH THE DISPLAY:
cd ~
sudo pip3 install --upgrade adafruit-python-shell click
sudo apt-get install -y git
git clone https://github.com/adafruit/Raspberry-Pi-Installer-Scripts.git
cd Raspberry-Pi-Installer-Scripts
sudo python3 adafruit-pitft.py --display=st7789_240x240 --rotation=0 --install-type=console
Your work is VERY appreciated along with everyone else working on this as it really helps open up portable use implementations of these SBC’s. Please help me with either a simple “yep” or NOPE to get started if you read this.
this version of lcd st7789 is compatible with this image radxa-zero3_debian_bullseye_xfce_b6.img?
hi @houssemmiled, I was able to make the st7735r lcd work on the radxa zero 3w simply by adding an overlay for it (adapted from rk3568-spi3-m0-cs0-waveshare35.dts) (fbft and drivers for st7735r and st7789v are already in the kernel).
The overlay I used is radxa-zero3-spi3-lcd.zip (797 Bytes)
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Hi, do you have any idea how could I make this overlay to Rock 3C ?
You need to select the corresponding driver according to your screen display ic and touch ic.
As for overlay dts, you can refer to this overlay script.
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Hi, thank you for the response.
If I activate this overlay script. But had no succes.
Later, I have downloaded the GIT folder (https://github.com/mrkprdo/radxa-zero-lcd-driver-installer) so I modified the meson-g12a-spi-st7735r file to contain the correct pinout that I am using:
// configure pin assigment below
reset-gpios = <0x30 113 1>; // pin 22
dc-gpios = <0x31 106 0>; // pin 18
led-gpios = <0x31 104 0>; // pin 15
After that, I uploaded it to Rock-3c and then ran:
$ sudo ./build.sh -t st7735r -c
However, it fails at the end when moving the created files:
make[1]: Leaving directory '/usr/src/linux-headers-5.10.160-38-rk356x'
Done building.
Installing dto files and kernel driver
cp: cannot create regular file '/boot/dtbs/5.10.160-38-rk356x/amlogic/overlay':
No such file or directory
FATAL ERROR: Couldn't open "/boot/dtbs/5.10.160-38-rk356x/amlogic/overlay/meson-g12a-spi-st7735r.dts" file or directory.
It fails at this installer step:
then
echo “Installing dto files and kernel driver”
echo “$PASSWORD” | sudo -S cp {fb_$TARGETDRIVER.ko,fbtft.ko} /usr/lib/modules/$KERNELVERSION/kernel/drivers/staging/fbtft/
echo “$PASSWORD” | sudo -S cp …/meson-g12a-spi-$TARGETDRIVER.dts $DTOPATH
echo “$PASSWORD” | sudo -S dtc -@ -I dts -O dtb -o $DTOPATH/meson-g12a-spi-$TARGETDRIVER.dtbo $DTOPATH/meson-g12a-spi-$TARGETDRIVER.dts
fi
I also tried copying the .dts files to directory /boot/dtbo/
$ sudo cp *.dts /boot/dtbo/
And running rsetup 's main interface.
But I have received this message: “can’t compile files”
I dont know what to do.
This is the file I have modifyed meson-g12a-spi-st7735r.dts
Hi, I can’t make it work.
Oh god.
What did I make wrong ?