ULX3S

A powerful ECP5 board for open source FPGA development

The ULX3S is a fully open source, compact, robust and affordable FPGA board equipped with a balanced spectrum of extra components and expansions. Although primarily developed as a teaching tool for mastering the principles of digital circuit design ¹, a wide selection of useful features and interfaces enables it to serve as a broad spectrum module for installation in complex devices.

ULX3S uses powerful Lattice Semiconductor ECP5 series FPGA chip supported by the latest open-source toolchains. This makes the ULX3S one of the most powerful and desirable platforms for FPGA enthusiasts available today. ULX3S comes equipped with onboard WiFi, display, buttons, LEDs and storage. Flash it using the WiFi connection (over-the-air update), or with one of the bitstreams stored on SD card and browsed by onboard OLED display and buttons. Due to its battery-backed RTC, it can power down completely and wake up only on certain events making it useful for low power applications such as battery-powered remote sensor nodes. And if you’re not of the low-power type, onboard peripherals such as SDRAM, USB, Digital video out, onboard FM/ASK antenna, ADC and DAC can make it audio/video powerhouse for signal processing and synthesis, motor control or SDR cases. You can emulate arcade machines or retro computers like Minimig(Amiga) or modern systems like F32C (MIPS/RISCV). It has 56 GPIO pins, all routed as differential pairs and a PMOD compatible pinout, opening it to a wide range of expansion options. If you are just starting with FPGA, you can also use the ULX3S as powerful Arduino and program it using Arduino IDE in seconds.

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

^{1 ULX3S is beeing actively used in Digital Logic class at the University of Zagreb Faculty of Electrical Engineering and Computing, Croatia}

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Features

FPGA Lattice ECP5 LFE5U-85F-6BG381C (84K LUT)
USB FTDI FT231XS (500kbit JTAG and 3Mbit USB-serial)
GPIO 56 pins (28 differential pairs), PMOD-friendly with power out 3.3V/1A 2.5V/1.5A
RAM 32MB SDRAM 166 MHz
Flash 4–16MB Quad-SPI Flash for FPGA config and user data storage
Mass storage Micro-SD slot
LEDs 11 (8 user LEDs, 2 USB LEDs, 1 WiFi 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 Diferential Interface) with 3.3V-5V I2C bidirectional level shifter
Display placeholder for 0.96" SPI COLOR OLED SSD1331
WiFi+bluetooth placeholder for ESP-32 (Standalone JTAG web interface over WiFi)
Antenna 27, 88–108, 144, 433 MHz FM/ASK onboard
ADC 8 channels, 12 bit, 1 MSa/s MAX11125
Power 3 Switching voltage regulators: 1.1V, 2.5V, 3.3V
Clock 25 MHz onboard, external differential clock input
Low power sleep 5uA/5V standby, RTC MCP7940N clock wake-up, power button, 32768 Hz quartz with CR1225 battery backup
Dimensions 94 × 51 mm

Comparison chart

	ULX3S	Lattice ECP5™ Evaluation Board	Lattice ECP5™ Versa	TinyFPGA EX	FleaFPGA 'Ohm'	KONDOR AX
License	OSHW	Proprietary	Proprietary	OSHW	OSHW	Proprietary
Price Range	$60–$200	$100	$250	not yet released	$45	$1500–$2000?
Schematics Published?	Yes	Yes	Yes	Yes	Yes	Yes
Design Files Published?	Yes	No	No	Yes	No	No
Physical Dimensions	94 × 51 mm	180 × 100 mm	165 × 110 mm	61 × 18 mm	65 × 30 mm	180 × 130 mm
FPGA
Model	ECP5 12F ECP5 25F ECP5 45F ECP5 85F	ECP5 85F	ECP5 45F	ECP5 12F ECP5 45F ECP5 85F	ECP5 25F	ECP5 85F
LUT Capacity	12K–84K	84K	44K	12K–84K	24K	84K
Embeded Memory (Kbits)	3744 (on 85F)	3744	1944	3744 (on 85F)	1008	3744
PERIPHERALS
USB-Serial JTAG	FT231X	FT2232H	FT2232	None	FT230X	FT2232
Programming over	USB-JTAG, EXT-JTAG, WiFi-ESP32-JTAG, SD-ESP32-JTAG	USB-JTAG, EXT-JTAG	USB-JTAG, EXT-JTAG	USB-bootloader, EXT-JTAG	USB-JTAG, EXT-JTAG	USB-JTAG, EXT-JTAG
Direct USB to FPGA	Yes	No	No	Yes	Yes	No
User IOs	56	178	Unknown	42	29	365
PMOD connector placeholders	4	1	No	No	No	No
User Buttons	7	3	2	1	No	2
DIP Switches	4	8	8	No	No	10
User LED	8	8	8	1	1	8
Indicator LED	3	9	10	1	No	6
Onboard Clock	25MHz	12MHz 50MHz 200MHz	100MHz	48MHz 200MHz	25MHz	100MHz
Flash	32–128 Mbit QSPI	128 Mbit QSPI	128 Mbit QSPI	64 Mbit QSPI	8 Mbit SPI	64 Mbit QSPI
Onboard RAM	32MB SDRAM	No	1024MB DDR3	up to 16MB HyperRAM	32MB SDRAM	512MB DDR3
Video Out	Digital (GPDI), Analog Composite PAL/NTSC (3.5 mm jack)	No	No	No	Digital (GPDI)	Digital (HDMI)
Audio Out	Digital S/PDIF (3.5mm jack), Digital (GPDI), Analog stereo (3.5 mm jack)	No	No	No	Digital (GPDI)	Digital (HDMI)
ADC	MAX11125	No	No	No	Sigma-Delta	No
Storage	Micro-SD	No	No	Micro-SD	Micro-SD	Micro-SD, 8GB eMMC
Ethernet	Possible over: ESP32, USB	No	Yes	No	No	Yes
Display	Placeholder for 0.96" SPI color OLED SSD1331	No	14-segment LED	No	No	No
Antenna	27, 88–108, 144, 433 MHz FM/ASK onboard	No	No	No	No	No
RTC (Real-time Clock)	MCP7940N, Low Power Sleep, Wakeup	No	No	No	No	No
POWER
Power Input	USB 5V	12V	12V	USB 5V	USB 5V	12V
GPIO bank voltage levels	3.3V, 2.5V (jumper selectable)	3.3V	3.3V	3.3V	3.3V	3.3V
Power reserve to drive external circuits	3.3V/1A 2.5V/1.5A	?	?	?	?	?
OTHER FEATURES
Differential Pairs	28	9	Unknown	No	12	Header
Single-ended only	5	178	Header	42	29	Header
SERDES	0	9	1	0, 2 (only EX85-5G variant)	0	4
SOFTWARE
Open Source Toolchain	Yes	Yes	Yes	Yes	Yes	Yes
Arduino support (FPGArduino)	Yes	Not yet	Not yet	Not yet	Yes	Yes
Confirmed working retro games consoles	Yes	No	No	No	Yes	No

Comparison chart was produced from currently available data. If you find any error in the specifications, or if you would like to see additional boards compared to ULX3S – let us know.