SPI to 4x UART Bridge - MULTIUART

Expand Your Microcontroller with 4 New Serial Ports Over SPI

Running out of hardware serial (UART) ports is a common roadblock in electronics design. Essential modules like Wi-Fi, Bluetooth, GPS, and cellular all demand dedicated UART connections—yet most modern microcontrollers and single-board computers (like the Raspberry Pi) offer only one or two. Upgrading to a higher-pin-count microcontroller often forces a full codebase rewrite.

This expansion board eliminates the bottleneck by converting a single SPI connection into four fully independent, buffered UART channels.

Key Features

• Stackable Architecture: Need more than four ports? Stack additional boards on top to expand to 8, 12, or more channels without sacrificing pin efficiency.
• 1 KB Dual Buffering: Every UART channel features dedicated 1,000-byte TX and RX buffers to prevent buffer overruns and dropped packets during heavy, simultaneous traffic.
• Smart Visual Feedback: An onboard LED shifts dynamic brightness levels to give you at-a-glance status for power, UART activity, and active SPI bus communication.
• Flexible Dual-Voltage Compatibility:
• Runs natively on 3.3V power.
• Features 5V-tolerant SPI and UART RX inputs.
• 3.3V TX outputs driver targets seamlessly on both 3.3V and 5V logic levels without requiring external level shifters.
• RS232 Support: Integrates cleanly with standard interface chips (like the MAX232) for legacy RS232 communications.

Simple, Single-Byte Command Structure

Skip register-heavy configuration. The board uses a streamlined, low-overhead single-byte command system to handle real-time control:

• Query remaining buffer space dynamically
• Execute block read/write operations
• Adjust baud rates on the fly

Supported Baud Rates: 1200 | 2400 | 4800 | 9600 | 19200 | 38400 | 57600 | 115200

What’s New in Version 2

Version 2 introduces a lower-profile processing IC that improves manufacturing reliability, reduces component waste, and keeps production costs low. 100% backward compatible with Version 1 hardware and software setups.

Software & Firmware Support

• Out-of-the-Box Libraries: Includes pre-built software support for both Arduino and Flowcode.
• Arduino IDE Library: Named MULTIUART and designed to create a stream that is compatible with other serial based libraries e.g. GPS/GSM.
• Upgradeable Firmware: In-system firmware updates can be flashed via a PICkit 3 header.