PicoBeam: A Raspberry Pi Pico 2 based VGA Display

This project demonstrates how to drive a VGA display using the Raspberry Pi Pico 2. The display uses a 640x480 pixel resolution with 16 colors (4-bit color depth). The Raspberry Pi Pico communicates with the display via a single 8-bit interface latch and provides debugging via UART.

Features

• Resolution: 640 x 480 pixels
• Builtin Font: Original Philips P2000C 12x8 bitmap font
• Bitmapped graphics: Support for printing individual pixels to the screen
• Color Depth: 4-bit (16 colors)
• Refresh Rate: ~72 Hz (using a 150 MHz clock with a x5 clock divider)
• Interface: Single 8-bit latch for display control
• UART: For debugging and communication
• Beeper: 1-bit beeper for simple audio feedback

Warning

Do not connect this board to a CRT monitor unless you are absolutely sure that the monitor supports 72 Hz vertical sync at 640x480 resolution. Connecting this board to a CRT that does not support these specifications may cause damage to the monitor or result in display instability. Always check your CRT monitor's specifications to confirm compatibility with 72 Hz VSync at 640x480 resolution before proceeding.

How It Works

The Raspberry Pi Pico drives the display by receiving pixel data through an 8-bit latch interface, which updates the screen in real-time. By connecting the Pico to the data bus of a CPU or microcontroller, instructions can be sent to the Pico.

Compilation instructions

Toolchain

sudo apt install cmake gcc-arm-none-eabi libnewlib-arm-none-eabi build-essential libstdc++-arm-none-eabi-newlib
sudo git clone https://github.com/raspberrypi/pico-sdk.git /opt/pico-sdk
sudo git -C /opt/pico-sdk submodule update --init
RUN 'export PICO_SDK_PATH=/opt/pico-sdk' | tee -a /etc/profile.d/pico-sdk.sh

Compiling

mkdir build && cd build
cmake ../src
make -j

Instruction delays

The Pico requires a bit of processing time and one should be cautious not to sent the data too fast. The following timings were found to give stable results when using a simple (slow) voltage divider circuit. When connecting the Pico to your specific setup, it is recommended to perform your own calibration to find which delays provide stable results.

Operation	Delay (μs)
Single characters	150
Large instructions (e.g., beeper or screen clear)	2000