How to use st7735 LCD SPI screen?

#1

Hi.
I saw some discution about SPI LCD.

I Have a ROCK3C with latest Debian.

How do I proceed?

Any tutorial ?

I need to implement into python script to image showing.

#2

There are two methods to display the ST7735 SPI LCD: one is through the kernel Overlay, and the other is calling the kernel-exposed /dev/spidevx.x device from the user layer to read and write to the spidev.

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#3

If you are interested in using the second method, you need to enable the spidev overlay first, and then install the related python libraries.

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#4

Hello friend,
Thanks for the answer.
First of all, I’ve been researching about SPI and found a post commenting on conflicts with libmraa.

I would like help deciding which libraries to use. I have no experience with ROCK.

Board: Radxa Rock 3C
System: Debian (latest)
Use - Recording USB video and audio input
Extras:

  1. 3-pin button (GND, VCC, out). To start recording.
  2. LEDs for feedback (app on)
  3. SPI ST7735 1.8 inch LCD display 128x160

First question:
I’m going to use the button to start the recording process. Within a python script.
I used the MRAA library. It works.
Is there another option for use in python?

Second question:
How to use the SPI screen to give feedback on what happens in my APP.
I have no idea how to get started in Rock. I made it work in other projects but following instructions.
I installed: https://github.com/pimoroni/st7735-python
But it didn’t work.
Apparently I should activate spidev.
Can you give me some guidance on how to follow?

Thanks.

#5
  1. you can also use python periphery.
  2. As for how to look at the screen feedback, this may depend on the specific logic in your program.
  3. The st7735-python library may depend on Adafruit_GPIO or RPI.GPIO, both of which are not compatible with the ROCK 3C.
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#6

if you want to enable st7735 from kernel driver, you can refer to this commit.

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#7
  1. Nice, thank you for the sugestion.
  2. yep. This is ok already.
  3. I saw that. I have discovered that st7735 python, uses RPI.GPIO and its not compatible.

But now, I dont know how to proceed.

#8

How do I start using this kernel driver?

After installing how do I display an image into the screen?

I really don’t have any idea how to start.

#9

This files contain:
#include “st7789v.dtsi”

DISPLAY_SPI {
status = “okay”;
#address-cells = <1>;
#size-cells = <0>;

st7789: st7789@0 {

I should change to st7735 ?
Sorry but I really couldn’t understand this part.

#10

I’ve just updated the dts script to work better with other models of the same type.
You can refer the following steps:

  1. clone my repository by the cmd:
git clone https://github.com/nascs/overlays.git
  1. checkout the branch
cd overlays
git checkout -b spi_lcd_st7735 origin/spi_lcd_st7735
  1. install the rk356x header package
wget https://github.com/radxa-pkg/linux-rk356x/releases/download/5.10.160-37/linux-headers-5.10.160-37-rk356x_5.10.160-37-ff919543b_arm64.deb
sudo apt install ./linux-headers-5.10.160-37-rk356x_5.10.160-37-ff919543b_arm64.deb
  1. compile overlays
make build-dtbo -j$(nproc) KERNELRELEASE=5.10.160-37-rk356x CONFIG_ARCH_MESON=n CONFIG_CPU_RK3528=rockchip CONFIG_CPU_RK3568=rockchip
  1. copy the st7735 overlay to directory /boot/dtbo/
 sudo cp arch/arm64/boot/dts/rockchip/overlays/rk3568-spi3-m1-cs0-st7735.dtbo /boot/dtbo/

  1. reboot you system

  2. if the compatible filed is not comatible with your lcd, just use this field in the comments section.

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Working SPI Display
#11

If the LCD works rightly, then you can operate the fb device “/dev/fbX”.

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#12

Hi, thank you for the help.

I did this mentioned. Had to use the // compatible = "sitronix,st7735r"; field mentioned to start the driver.

I have done only a simple correction in width = <135>; and height = <240> and 4MHz;
Compiled, copied, and rebbot. Then installed in rsetup.

Now I can see the screen “working” it’s all white.
rock@rock-3c:~/scripts$ sudo dmesg | grep fb_st7735r
[ 15.989671] fb_st7735r: module is from the staging directory, the quality is unknown, you have been warned.
[ 15.990464] fb_st7735r spi3.0: fbtft_property_value: width = 128
[ 15.990477] fb_st7735r spi3.0: fbtft_property_value: height = 160
[ 15.990483] fb_st7735r spi3.0: fbtft_property_value: regwidth = 16
[ 15.990489] fb_st7735r spi3.0: fbtft_property_value: buswidth = 8
[ 15.990496] fb_st7735r spi3.0: fbtft_property_value: debug = 0
[ 15.990502] fb_st7735r spi3.0: fbtft_property_value: rotate = 90
[ 15.990508] fb_st7735r spi3.0: fbtft_property_value: fps = 60
[ 15.990513] fb_st7735r spi3.0: fbtft_property_value: txbuflen = 32768
[ 17.487988] graphics fb0: fb_st7735r frame buffer, 160x128, 40 KiB video memory, 32 KiB buffer memory, fps=60, spi3.0 at 4 MHz

I have tryed to use it with this code with no succes:
sudo dd if=/dev/zero of=/dev/fb0 bs=10k count=1

This also makes no change:
sudo dd if=/dev/zero of=/dev/fb0 bs=10k count=1

As far as I know I have to initiate the screen, reset, and then send an image. But I was doing this steps with python, I dont know how to make this.

#13

When I try:
ffmpeg -i cat.jpg -f rawvideo -pix_fmt rgb24 -r 60 -s 160x128 /dev/fb0
convert cat.jpg -depth 8 -colorspace RGB -format raw - | sudo dd of=/dev/fb0

Both don’t work.
rock@rock-3c:~/scripts$ convert cat.jpg -depth 8 -colorspace RGB -format raw - | sudo dd of=/dev/fb0
[sudo] password for rock:
51+1 records in
51+1 records out
26435 bytes (26 kB, 26 KiB) copied, 0.000352335 s, 75.0 MB/s

Also, I Can’t see the display when: ls /dev/spidev*
should I enable spi overlay also?