A powerful, open hardware ECP5 FPGA dev board

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ULX3S is a fully open source, compact, robust, and affordable FPGA dev board equipped with a balanced selection of additional components and expansions. Although it was designed primarily as a teaching tool for mastering the principles of digital circuit design, ULX3S incorporates a wide array of features and interfaces that allow it to serve as a broadly useful module for installation in complex devices.

Built around a powerful Lattice Semiconductor ECP5-series FPGA chip and supported by the latest open-source toolchains, ULX3S is one of the most powerful and desirable platforms available for FPGA enthusiasts. It comes equipped with onboard Wi-Fi, display, buttons, LEDs, and storage. Flash it with an over-the-air (OTA) update using the Wi-Fi connection or take advantage of the onboard OLED display and buttons to browse the contents of an SD card and select a bitstream. Due to its battery-backed RTC, ULX3S can power down completely and wake up only in response to certain events. This feature makes it perfect for use in low-power applications such as battery-powered remote sensor nodes.

And if you’re not the low-power type, onboard peripherals like SDRAM, USB, digital video out, onboard FM/ASK antenna, ADC, and DAC make it an audio/video powerhouse for signal processing and synthesis, motor control, and SDR use cases. It can emulate arcade machines and retro computers like the Minimig (Amiga) or modern systems like the F32C (MIPS/RISCV). It has 56 GPIO pins, all routed as differential pairs, and a PMOD compatible pinout, which opens it up to a wide range of expansion options. And if you are just starting out FPGAs, you can use the Arduino IDE to program ULX3S in seconds.

ULX3S has been actively developed since 2016 and is the result of a collaboration between Radiona.org / Zagreb Makerspace and FER – the Faculty of Electrical Engineering and Computing – at the University of Zagreb in Croatia.

PCB design was authored by Electronic Mechanic Aerodynamic Research & Development (EMARD).

Features & Specifications

  • FPGA: Lattice ECP5
    • LFE5U-85F-6BG381C (84 K LUT)
    • LFE5U-45F-6BG381C (44 K LUT)
    • LFE5U-25F-6BG381C (24 K LUT)
    • LFE5U-12F-6BG381C (12 K LUT)
  • USB: FTDI FT231XS (500 kbit JTAG and 3 Mbit USB-serial)
  • GPIO: 56 pins (28 differential pairs), PMOD-friendly with power out 3.3 V at 1 A or 2.5 V at 1.5 A
  • RAM: 32 MB SDRAM 166 MHz
  • Flash: 4-16 MB Quad-SPI Flash for FPGA config and user data storage
  • Mass Storage: Micro-SD slot
  • LEDs: 11 (8 user LEDs, 2 USB LEDs, 1 Wi-Fi LED)
  • Buttons: 7 (4 direction, 2 fire, 1 power button)
  • Audio: 3.5 mm jack with 4 contacts (analog stereo + digital audio or composite video)
  • Video: Digital video (GPDI General-Purpose Differential Interface) with 3.3 V to 5 V I²C bidirectional level shifter
  • Display: Placeholder for 0.96" SPI COLOR OLED SSD1331
  • Wi-Fi & Bluetooth: Placeholder for ESP32 (standalone JTAG web interface over Wi-Fi)
  • Antenna: 27, 88-108, 144, 433 MHz FM/ASK onboard
  • ADC: 8 channels, 12 bit, 1 MS a/s MAX11125
  • Power: 3 Switching voltage regulators: 1.1 V, 2.5 V, and 3.3 V
  • Clock: 25 MHz onboard, external differential clock input
  • Low-Power Sleep: 5 µA at 5 V standby, RTC MCP7940N clock wake-up, power button, 32768 Hz quartz with CR1225 battery backup
  • Dimensions: 94 mm × 51 mm


Comparison Table

ULX3S Lattice ECP5 Evaluation BoardLattice ECP5 VersaTinyFPGA EXFleaFPGA 'Ohm'KONDOR AX
LicenseOSHW ProprietaryProprietaryOSHWOSHWProprietary
Price Range$60 – $200 $100$250not yet released$45$1500 – $2000?
Schematics Published?Yes YesYesYesYesYes
Design Files Published?Yes NoNoYesNoNo
Physical Dimensions94 × 51 mm 180 × 100 mm165 × 110 mm61 × 18 mm65 × 30 mm180 × 130 mm
ModelECP5 12F ECP5 25F ECP5 45F ECP5 85F ECP5 85FECP5 45FECP5 12F ECP5 45F ECP5 85FECP5 25FECP5 85F
LUT Capacity12 K – 84 K 84 K44 K12 K – 84 K24 K84 K
Embeded Memory (Kbits)3744 (on 85F) 374419443744 (on 85F)10083744
USB-Serial JTAGFT231X FT2232HFT2232NoneFT230XFT2232
Direct USB to FPGAYes NoNoYesYesNo
User IOs56 178Unknown4229365
PMOD Connector Placeholders4 1NoNoNoNo
User Buttons7 321No2
DIP Switches4 88NoNo10
User LED8 88118
Indicator LED3 9101No6
Onboard Clock25 MHz 12 MHz 50 MHz 200 MHz100 MHz48 MHz 200MHz25 MHz100 MHz
Flash32–128 Mbit QSPI 128 Mbit QSPI128 Mbit QSPI64 Mbit QSPI8 Mbit SPI64 Mbit QSPI
Onboard RAM32 MB SDRAM No1024 MB DDR3up to 16 MB HyperRAM32 MB SDRAM512 MB DDR3
Video OutDigital (GPDI), Analog Composite PAL/NTSC (3.5 mm jack) NoNoNoDigital (GPDI)Digital (HDMI)
Audio OutDigital S/PDIF (3.5 mm jack), Digital (GPDI), Analog stereo (3.5 mm jack) NoNoNoDigital (GPDI)Digital (HDMI)
ADCMAX11125 NoNoNoSigma-DeltaNo
StorageMicro-SD NoNoMicro-SDMicro-SDMicro-SD, 8 GB eMMC
EthernetPossible over: ESP32, GPDI, USB NoYesNoNoYes
DisplayPlaceholder for 0.96" SPI color OLED SSD1331 No14-segment LEDNoNoNo
Antenna27, 88–108, 144, 433 MHz FM/ASK onboard NoNoNoNoNo
RTC (Real-time Clock)MCP7940N, Low Power Sleep, Wakeup NoNoNoNoNo
Power InputUSB 5 V 12 V12 VUSB 5 VUSB 5 V12 V
GPIO Bank Voltage Levels3.3 V, 2.5 V (jumper selectable) 3.3 V3.3 V3.3 V3.3 V3.3 V
Power Reserve to Drive External Circuits3.3 V / 1 A, 2.5 V / 1.5 A ?????
Other Features
Differential Pairs28 9UnknownNo12Header
Single-Ended Only5 178Header4229Header
SERDES0 910, 2 (only EX85-5G variant)04
Open Source ToolchainYes YesYesYesYesYes
Arduino Support (FPGArduino)Yes Not yetNot yetNot yetYesYes
Confirmed Working Retro Games ConsolesYes NoNoNoYesNo

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