Sometimes you just want a simple FPGA development board with a low-cost FPGA and some I/O pins, this is one of those boards.

The board contains an Efinix T20Q100F3C4 FPGA which provides excellent value for money. In addition, the FPGA comes in a "makers" friendly LQFP package and is readily available for around £10 (DigiKey). The Place and Route software is freely available from Efinix.

The board uses 4 layers with all the components on one side. The price different between a 2 and 4 layers was small but having components on both sides did increase the price. A tiny STM32C071 (less than £1 from LCSC) was added which acts as the programmer (USB to SPI bridge), clock oscillator, IP communication and soft switches.

Board Specification:

- FPGA Efinix T20Q100F3C4, 19728 Luts, 1020Kbit Memory, 36 Multipliers, 5 PLL, 16Mbit Flash

- Easy programmable and powered via USB-C, no drivers required!

- Programs can be loaded into Ram or Flash memory

- Sapphire RISC-V core @111MHz using just 16% of the FPGA LUTs

- 8..48MHz clock (PLL input), optional 32KHz Clock

- 47 3.3volt I/O pins divided over 3 IDC connectors

- 17 FPGA pins can be toggled/monitored via USB-C

- IP Core communication via USB-C (UART2UART bridge)

- Optional 8MByte ESP-PSRAM64H memory chip (or 2MByte APS1604M-3SQR)

- On-Board tiny STM32C071 microcontroller to control the FPGA

- Small, less than credit card size (71mm x 48mm)

- All components on one side, smallest SMD 0603

- Except for the T20Q100 (DigiKey) all components can be source from LCSC Electronics

The board can be programmed over USB-C without requiring any drivers. The on-board microcontroller implements a UART to SPI bridge so all you need is a simple program (supplied in C-code) to upload the hex file produced by the Efinix Efinity P&R tool.

You also don't need an extra USB to TTL converter as the microcontroller provides an extra UART2UART bridge. This allows you to connect a UART implemented on the FPGA with a PC based terminal.

The only programming dongle you need is for the STM32 microcontroller, luckily they are very cheap (£3) on eBay/Aliexpress/Amazon etc.A ready made image implementing the above is functionality is provided..

More information and example code can be found on my github page: https://github.com/htminuslab/Efinix_T20_Dev_Board