3.5-inch Display (Resistive Touch)
- Video Tutorial
The official WalnutPi 3.5-inch display (resistive touch) uses the SPI bus with a maximum speed of up to 80MHz. The backlight is controllable. Using the official driver, you can achieve desktop display and other UI functions.
WalnutPi does not currently support other Raspberry Pi 3.5-inch displays on the market.
The back side routes GPIO through SMT flat cables, meaning you can still connect I2C, serial communication devices, and other modules even with the display attached.
| Specifications | |
|---|---|
| Resolution | 480x320(Pixel) |
| Interface | 4-wire SPI (Max Speed: 80MHz) |
| Display IC | st7796 |
| Touch Panel | XPT2046 (Resistive Touch) |
| Operating Temperature | -20℃ ~ 60℃ |
| Storage Temperature | -30℃ ~ 70℃ |
| Dimensions | 83x55mm |
| Weight | 75g |
- Pin Description:
| Pin | Label | Description |
|---|---|---|
| 1,17 | 3.3V | Power Positive (3.3V Input) |
| 2,4 | 5V | Power Positive (5V Input) |
| 6,9,14,20,25 | GND | Power Ground |
| 11 | TP_IRQ | Touch Panel Interrupt, Outputs Low When Pressed |
| 18 | LCD_DC | Command/Data Selection, Low for Command, High for Data |
| 19 | SPI_MOSI | LCD SPI Data Input |
| 21 | SPI_MISO | Touch Panel SPI Data Output |
| 22 | RST | Reset |
| 23 | SPI_CLK | LCD/Touch Panel Clock Signal |
| 24 | LCD_CS | LCD Chip Select, Active Low |
| 26 | TP_CS | Touch Panel Chip Select, Active Low |
Enabling LCD Display
The WalnutPi system already includes the relevant display driver, supported on both desktop and non-desktop versions. Use the following command to enable desktop display (TAB key auto-completion supported):
sudo set-lcd lcd35-st7796 install
Restart the board after configuration:
sudo reboot
Unplug the HDMI cable, wait patiently for the system to start, and you will see the desktop interface on the LCD (terminal for non-desktop system), displayed in the following default orientation:
The above command is applicable to both WalnutPi desktop and non-desktop systems (the non-desktop system will display a terminal). After this configuration, if an HDMI display is connected, the display takes priority. To view on the LCD, be sure to unplug the HDMI cable.
Setting LCD Display Orientation
Use the following command to set the display orientation. Supported angles: 0, 90, 180, 270 degrees. The default is 270 degrees. For desktop systems, 270 or 90 is recommended as portrait orientation may cause content loss.
sudo set-lcd lcd35-st7796 set_rotate 270
Disabling LCD Display
Use the following command to remove the LCD display function and boot from HDMI:
sudo set-lcd lcd35-st7796 remove
Using on Raspberry Pi
The WalnutPi 3.5-inch touch display provides driver software adapted for the Raspberry Pi. Once installed, it can be used on the Raspberry Pi. See the README document in the project for detailed usage instructions:
Project link: https://github.com/walnutpi/rpi-lcd
