vncviewer VNC Viewer

A lightweight VNC viewer that renders a remote desktop on an LCD display via the NuttX LCD character device interface (/dev/lcd0).

Features:

  • RFB 3.8 protocol with VNC Authentication (pure software DES, no external library)

  • Auto-detect pixel format from LCD driver

  • Raw encoding with row-by-row rendering — minimal RAM usage

  • Automatic reconnection on disconnect

Prepare

  • Enable the VNC Viewer application (Device):

    CONFIG_NET_TCP=y
CONFIG_LCD=y
CONFIG_SYSTEM_VNCVIEWER=y

  • Ensure the device has a working LCD driver (/dev/lcd0) and TCP/IP network connectivity.

  • Install a VNC server on the host. For example, on Ubuntu:

    sudo apt install x11vnc xvfb openbox xterm

Usage

vncviewer [options] <host> [port]

Options:

  • -p <password> — VNC password

  • -d <devno> — LCD device number (default: 0)

  • -h — Show help

Default port: 5900

Host VNC Server Configuration

Three server modes are supported:

1. Xvfb Virtual Desktop (Pixel-Perfect 1:1)

Create a virtual framebuffer matching the LCD resolution (e.g., 320×240):

# Start virtual display
Xvfb :1 -screen 0 320x240x16 &
DISPLAY=:1 openbox &
DISPLAY=:1 xterm -geometry 38x11+0+0 -fa Monospace -fs 10 &

# Start VNC server
x11vnc -display :1 -rfbport 5901 -passwd mypasswd -shared -forever -xkb -add_keysyms -bg

On the device:

vncviewer -p mypasswd <host_ip> 5901
../../../_images/vncviewer_xvfb.png

Xvfb virtual desktop — host side (320×240 xterm in VNC viewer)

../../../_images/vncviewer_xvfb_lcd.jpg

Xvfb virtual desktop — device side (rendered on ST7789 LCD)

2. Physical Desktop Clip (Top-Left Region)

Clip a region of the physical desktop matching the LCD resolution:

x11vnc -display :0 -rfbport 5901 -passwd mypasswd -shared -forever -xkb -add_keysyms -bg -clip 320x240+0+0

On the device:

vncviewer -p mypasswd <host_ip> 5901

3. Physical Desktop Scaled

Scale the full desktop down to the LCD resolution:

x11vnc -display :0 -rfbport 5901 -passwd mypasswd -shared -forever -xkb -add_keysyms -bg -scale 320x240

On the device:

vncviewer -p mypasswd <host_ip> 5901

Examples

Connect to a VNC server with password:

vncviewer -p mypasswd 192.168.1.100 5901

Connect using a different LCD device:

vncviewer -d 1 -p mypasswd 192.168.1.100 5900