IOX-77: The New King of I/O
The IOX-77 board features an ESP32-C3 and five CH32V003 co-processors to provide 75 GPIO pins and six cores for complex embedded projects.
ESP32 chips are inexpensive, powerful, accessible, and loaded with features, making them some of the best microcontrollers around for makers. But what can you do when your project grows too large for a typical ESP32 development board? The two dozen or so onboard GPIOs go a long way, but eventually everyone is going to find that they need more.
A new open-source development board created by Dieu-de-l-elec that is named IOX-77 offers far more GPIO pins than a typical development board. Equipped with an ESP32-C3 microcontroller, the IOX-77 offers 75 available GPIO pins. The ESP32-C3 itself doesn’t have that many GPIO pins, so the board relies on an additional five CH32V003 chips to increase the count.
Rather than using traditional GPIO expanders, the IOX-77 uses five CH32V003 microcontrollers that communicate with the main ESP32-C3 over I2C, effectively acting as intelligent co-processors instead of passive expanders. This design allows each auxiliary chip to contribute up to 14 additional GPIOs while also running its own custom firmware. In practice, that means the IOX-77 behaves like a six-core system, where multiple tasks can execute in parallel across the ESP32 and the five RISC-V-based helper chips.
This architecture opens the door to more sophisticated embedded designs. Time-sensitive operations, repetitive I/O handling, or custom macros can be offloaded to the CH32V003 chips, freeing the ESP32 to focus on higher-level logic, networking, or Bluetooth communication. With 16KB of flash available on each auxiliary MCU, there is enough room for meaningful standalone functionality on every node.
Despite its expanded capabilities, the IOX-77 remains compact, measuring just 71 × 42 mm — slightly longer than an Arduino Uno but significantly smaller than boards like the Mega. It operates primarily at 3.3V, though 10 of its GPIOs are 5V tolerant, adding flexibility for interfacing with a wider range of components.
Dual 2x25 1.27mm headers expose all major signals, while additional FPC connectors provide alternative access to GPIO, I2C, and UART interfaces. A dedicated programming interface allows each CH32V003 to be flashed individually, and the ESP32 can reset or power-manage the auxiliary chips dynamically, enabling low-power operation when full performance isn’t needed.
On the software side, an Arduino-compatible library simplifies development by abstracting the distributed GPIO system. Developers can interact with pins using familiar functions like digitalWrite() and analogRead(), while the underlying firmware handles communication with the auxiliary microcontrollers.
By blending distributed processing with massive I/O expansion, the IOX-77 pushes beyond the limitations of traditional development boards. For makers and engineers building increasingly complex systems, it offers a powerful and flexible alternative without sacrificing affordability or accessibility. Further details are available in the project’s GitHub repository.