Custom LPC811 Controller for Alpha 4200C LED Message Display

I designed and built a custom embedded controller board for an Alpha 4200C / 4200C120 tri-color LED message display, a commercial 16×200 LED message sign originally designed for RS-232/RS-485 control.

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The goal of the project was to replace the original display control hardware with a compact custom board that could receive frame data from a Linux desktop and drive the LED matrix directly. I started by building and validating the circuit on a breadboard, then converted the design into a KiCad schematic and PCB layout, had the board fabricated, assembled it, and tested it on the final display.

 

​The controller uses an LPC811 Arm Cortex-M0+ microcontroller running firmware written in C. The LPC811 refreshes the LED display at 100 Hz, providing smooth and stable output. A Linux desktop application, also written in C, sends display data over a serial connection.

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Incoming serial data from the Linux PC is converted from RS-232 to logic-level UART using a MAX3232. The LPC811 processes that data and outputs the display control signals. Since the LPC811 operates at 3.3 V and the LED display expects 5 V logic, the output signals pass through an SN74HCT541 line driver to shift the signal levels up to the voltage required by the display hardware.

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The board is powered directly from the display assembly. A 5 V rail powers the SN74HCT541, while an MCP1700T regulator generates the 3.3 V rail used by the LPC811 and MAX3232. I also added a small programming/reset header so the LPC811 firmware can be updated directly through the serial interface.

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This project combined embedded C programming, Linux C development, serial communication, voltage-level translation, display timing, PCB design, hardware bring-up, and prototype-to-production workflow.