Developer Board Forgix: Raspberry Pi RP2354 Meets FPGA

Forgix is a $50 development board that can be combined with breadboards, combining the Raspberry Pi RP2354 microcontroller with an FPGA to provide hardware flexibility.

One of the most useful features of Raspberry Pi microcontrollers is their programmable input/output (PIO). With PIO, users can create custom hardware-level interfaces for time-critical applications such as controlling high-speed LEDs. This is particularly useful when a main processor needs to be kept free for processing application logic.

As useful as PIO blocks are, their capabilities are quite limited. When users need to develop more complex hardware-level interfaces, an FPGA is the right choice. The Forgix development board from Adiuvo Engineering combines the best of both worlds: a Raspberry Pi microcontroller and an FPGA. With this platform, developers can create complex devices.

The Best of Both Worlds

The board combines the Raspberry Pi RP2354 with an Efinix Trion T8F49 FPGA, which contains 7,384 logic elements, offering developers two different computing cores on a single board. The RP2354, with its two Arm Cortex-M33 cores, handles traditional firmware tasks, while the FPGA can be configured to implement custom digital hardware, high-speed signal processing pipelines, or specialized peripherals that would be difficult or impossible to achieve with software alone.

Forgix follows a Teensy-compatible form factor, which is small enough to fit on a breadboard or in embedded projects with limited space. The board also provides the standard interfaces of the RP2354, including SPI, I2C, UART, USB 1.1, and ADC, making integration with sensors, displays, and other peripherals easier.

The Raspberry Pi RP2354 microcontroller features 520 KB of on-chip SRAM. An external QSPI PSRAM chip provides additional memory for applications requiring more working memory. Integrated features include a USB-C port for power and programming, an addressable RGB LED for status indication, a user push button, and a Tag-Connect SWD header for hardware debugging.

Direct Loading of the Bitstream

Instead of requiring specialized programming hardware, Adiuvo Engineering has developed an open-source utility called "Forge FPGA Loader." A Python-based GUI or command-line tool transfers FPGA bitstreams generated by Efinity via a serial USB connection to the RP2354, which then directly forwards the data to the FPGA via SPI.

Since the bitstream is passed directly through the microcontroller instead of being fully stored in RAM first, the memory capacity of the RP2354 does not limit the FPGA configuration. Larger FPGA images can be loaded without using valuable application memory, significantly simplifying development.

With a price of 50 US dollars, Forgix lowers the entry barrier for experiments with FPGA-based hardware design. Instead of choosing between the flexibility of a microcontroller and the performance of programmable logic, developers can combine both on a single breadboard-compatible platform. Forgix boards are now available.