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Photonicat 2 LCD Display and Fan Support

Overview

The Photonicat 2 includes two important hardware features that require software support:

  1. LCD Display - GC9307 SPI LCD (172x320 pixels) showing system status
  2. Cooling Fan - PWM-controlled fan for thermal management

This document explains how to enable these features with vanilla OpenWrt.

📖 For comprehensive configuration guide: See guides/06-SCREEN_AND_FAN_DETAILED.md for complete documentation including all display configuration options, data keys, element types, color schemes, configuration examples, and detailed fan control options.

LCD Display Support

Hardware Specifications

  • Controller: GC9307 SPI LCD
  • Resolution: 172x320 pixels
  • Interface: SPI (SPI1)
  • GPIO Pins:
    • RST (Reset): GPIO 122
    • DC (Data/Command): GPIO 121
    • CS (Chip Select): GPIO 13
  • Backlight: PWM-controlled (PWM2)
  • Rotation: 180 degrees

Device Tree Support

The LCD is defined in the device tree (rk3576-photonicat2.dts):

  • SPI1 interface configuration
  • PWM backlight control
  • GPIO pin assignments

Display Application

The display is driven by pcat2_mini_display, a Go-based application that:

  • Renders system information to the LCD
  • Shows real-time stats (CPU, memory, network, battery)
  • Displays 5G modem status and signal strength
  • Shows SMS messages
  • Provides customizable screens
  • HTTP API for remote control

Repository: https://github.com/photonicat/photonicat2_mini_display

Required Packages

Add this to your configs/pcat2_custom.config:

# LCD Display Application (includes required kernel modules)
CONFIG_PACKAGE_pcat2-display-mini=y

Framebuffer support

CONFIG_PACKAGE_kmod-fb=y CONFIG_PACKAGE_kmod-fb-sys-fops=y

Additional display support

CONFIG_PACKAGE_kmod-backlight=y


### Building with Display Support

#### Option 1: Automatic Build (Recommended)

If you use the `./build.sh` script provided in this repository, the display package is **automatically copied** to the build environment, and the `configs/pcat2_custom.config` file already enables it.

Simply run:
```bash
./build.sh

Option 2: Manual Build

If you are building manually without the wrapper script:

  1. Copy the display package to OpenWrt build:

    # From your OpenWrt build root
mkdir -p package/custom
cp -r /path/to/photonicat2-support/packages/pcat2-display-mini package/custom/

  2. Enable in menuconfig:

    make menuconfig
# Navigate to: Utilities → pcat2-display-mini
# Press 'Y' to build into firmware or 'M' for module

  3. Or add to your config file:

    CONFIG_PACKAGE_pcat2-display-mini=y

  4. Rebuild:

    make -j$(nproc)

Option 3: Install Display Application Post-Install

If you've already flashed OpenWrt without the display package:

  1. On the device, install Go runtime (if not already in firmware):

    opkg update
opkg install golang

  2. Build and install manually:

    # Clone display application
git clone https://github.com/photonicat/photonicat2_mini_display
cd photonicat2_mini_display

# Build for ARM64
GOOS=linux GOARCH=arm64 go build -o photonicat2_mini_display

# Install
cp photonicat2_mini_display /usr/bin/
chmod +x /usr/bin/photonicat2_mini_display

# Copy assets
mkdir -p /usr/share/pcat2_mini_display
cp -r assets /usr/share/pcat2_mini_display/
cp config.json /etc/pcat2_mini_display-config.json

# Install init script (from photonicat2-support/packages/)
# ... or create systemd service

Display Customization

The display is highly customizable via config.json:

  • Update intervals: Control how often data is refreshed
  • Display pages: Choose which information screens to show
  • Colors and themes: Customize appearance
  • API endpoints: Configure data sources
  • Screen timeout: Battery vs AC power settings
  • SMS display: Enable/disable SMS notifications

Configuration file: /etc/pcat2_mini_display-config.json

Example customizations:

{
  "displayPages": ["system", "network", "battery", "modem"],
  "updateIntervals": {
    "system": 2,
    "battery": 1,
    "network": 2
  },
  "screenTimeout": {
    "onBattery": 60,
    "onDC": 86400
  }
}

HTTP API

The display application provides an HTTP API (default: port 8080):

  • View current stats: http://device-ip:8080/api/status
  • Control display: http://device-ip:8080/api/control
  • Upload custom graphics: http://device-ip:8080/api/upload

Fan Support

Hardware Specifications

  • Type: PWM-controlled cooling fan
  • Interface: PWM1 (channel 0)
  • Control: Automatic thermal management via kernel

Device Tree Support

The fan is configured in the device tree:

  • PWM1 interface
  • Thermal zone bindings
  • Cooling device integration

Thermal Management

The RK3576 SoC includes thermal zones with automatic fan control:

  • Thermal zones: CPU, GPU, NPU temperature monitoring
  • Cooling levels: Fan speed adjusts based on temperature
  • Thresholds: Defined in device tree

Required Kernel Modules

Add these to your configs/pcat2_custom.config:

# PWM support for fan
CONFIG_PACKAGE_kmod-pwm=y
CONFIG_PACKAGE_kmod-pwm-rockchip=y

# Thermal management
CONFIG_PACKAGE_kmod-thermal=y
CONFIG_PACKAGE_kmod-hwmon-core=y

Fan Control

Automatic Control (Default)

The fan is automatically controlled by the kernel thermal management:

  • Temperature sensors monitor SoC temperature
  • Fan speed increases as temperature rises
  • No manual configuration needed

Manual Control (Advanced)

For custom fan control:

  1. Check fan PWM device:

    ls /sys/class/pwm/

  2. Control fan speed manually:

    # Enable PWM
echo 0 > /sys/class/pwm/pwmchip0/export

# Set period (in nanoseconds)
echo 25000 > /sys/class/pwm/pwmchip0/pwm0/period

# Set duty cycle (0-25000 for speed control)
echo 12500 > /sys/class/pwm/pwmchip0/pwm0/duty_cycle  # 50% speed

# Enable
echo 1 > /sys/class/pwm/pwmchip0/pwm0/enable

  3. Monitor temperatures:

    # View all thermal zones
cat /sys/class/thermal/thermal_zone*/temp

# View specific zone
cat /sys/class/thermal/thermal_zone0/temp

Custom Fan Scripts

Create a fan control script in /etc/init.d/fan-control:

#!/bin/sh /etc/rc.common

START=99

start() {
    # Set fan to automatic mode
    echo 0 > /sys/class/pwm/pwmchip0/export 2>/dev/null
    echo 25000 > /sys/class/pwm/pwmchip0/pwm0/period
    echo 1 > /sys/class/pwm/pwmchip0/pwm0/enable
}

Testing

Test LCD Display

  1. Check SPI device:

    ls /dev/spidev*
# Should show: /dev/spidev1.0

  2. Check display service:

    /etc/init.d/pcat2-display-mini status

  3. View logs:

    logread | grep display

Test Fan

  1. Check PWM device:

    ls /sys/class/pwm/

  2. Monitor fan activity:

    watch -n 1 'cat /sys/class/pwm/pwmchip0/pwm0/duty_cycle'

  3. Stress test to trigger fan:

    # Install stress tool
opkg install stress-ng

# Run CPU stress
stress-ng --cpu 8 --timeout 60s

# Monitor temperature
watch -n 1 'cat /sys/class/thermal/thermal_zone0/temp'

Troubleshooting

LCD Not Working

Check SPI module:

lsmod | grep spi
# Should show: spi_rockchip, spidev

Manually load modules:

modprobe spi-rockchip
modprobe spidev

Check device tree:

ls /sys/firmware/devicetree/base/spi*/

Verify backlight:

ls /sys/class/backlight/
echo 255 > /sys/class/backlight/backlight/brightness

Fan Not Working

Check PWM module:

lsmod | grep pwm
# Should show: pwm-rockchip

Manually load PWM:

modprobe pwm-rockchip

Check thermal zones:

ls /sys/class/thermal/thermal_zone*/
cat /sys/class/thermal/thermal_zone*/type

Display Application Crashes

Check logs:

logread -f | grep pcat2

Run manually for debugging:

/etc/init.d/pcat2-display-mini stop
/usr/bin/photonicat2_mini_display -config /etc/pcat2_mini_display-config.json

Integration with Build System

To automatically include display and fan support in your build:

  1. Update build.sh to copy display package (already done in wrapper)
  2. Add required kernel modules to your config file
  3. Include init scripts in files/ directory
  4. Build and flash the complete image

Additional Resources

Security Note

⚠️ The display application includes an HTTP API. For security:

  • Change default ports in config
  • Use firewall rules to restrict access
  • Disable SMS features if not needed
  • Review the code before use in production

Summary

  • ✅ LCD: Supported via device tree + pcat2-display-mini application
  • ✅ Fan: Supported via device tree + automatic thermal management
  • ✅ Customizable: Both can be fully customized
  • ✅ Vanilla OpenWrt: Works with official OpenWrt + minimal patches