ULX4M

There are two versions of the ULX4M. The low cost ULX4M-LS will have SDRAM and a small FPGA. The high performance, more expensive, ULX4M-LD will have DDR3, 85K LUTs and 3.2Gps SerDes. To maximize memory bandwidth on the high performance ULX4M-LD SOM, the FPGA and high speed DDR3 SDRAM are on an expensive 6 layer circuit board.

The idea is to split the circuit board into two parts, the FPGA with memory, and a mass-produced base board. The base boards can be a Raspberry Pi 4 compute module base board such as the TOFU, or you can build an application specific base board for your needs. The initial base board reproduced the functionality of the ULX3S.

Multiple protocols including DisplayPort, multi Gbps Ethernet, PCIe, and MIPI can be supported by the four SerDes on the LD board. SerDes stands for SERializer DESerializer. SerDes takes a low speed parallel signal and serializes it into a single high speed differential pair running at up to 3.2 Gigabits per second (Gbps). That reduces the number of wires required. On Lattice ECP5, without overclocking, the internal signals are limited to 400 Mhz. Reportely with overclocking, the SerDes can reach 5Gbps on many chips. The ratio of the two speeds is called the gearing.

The differential signal has lower voltage swings then regular single ended signals. Power is proportional to the voltage swing squared, so it consumes a lot less power. It can run across twisted pairs or coaxial cable for longer distances than single ended signals. SerDes is less sensitive to noise, and generates less noise.

Low cost LS Variant

Lattice ECP5 LFE5U-12F-6BG381C

Ethernet 100Mbps: LAN8720A

32 MB SDRAM: IS42S16160G-7BL ( I could not find the link)

High Performance LD Variant

Lattice ECP5 LFE5U-85F-6BG381C Comes in multiple versions: 12, 25, 45 or 85K LUTs.

512MB DDR3: MT41K256M16TW-107

Ethernet 1Gbps: KSZ9031RNXCA

Both boards have the same FLASH chip:

W25Q128JVSIM NOR Flash spiFlash, 3V, 128M-bit, 4Kb Uniform Sector

Raspberry Pi 4 Compute Module Carrier Boards. View

The brilliant thing about the ECP5 ULX4M is that it can be mounted on a large number of commercially available carrier boards. Whatever your needs, you can probably avoid designing a complete circuit board, by reusing one of the existing carrier boards, or by making small changes to an existing carrier board.

Here is a huge list of Raspberry Pi Compute Module 4 Carrier boards. While. the title says "Raspberry Pi PCIe Database", really it is a list of carrier boards, a small part of a larger PCIe web site. Only the ones that look like they can be plugged into a computer back plane are actually for PCIe. The rest include everything you could ask for. Small ones, big ones, ones with cases, displays, clusters for many compute modules, game pads, and other things. Below are mentioned two of the more important ones for ULX4M users. If you are using different carrier board with the ULX4M, please let me know and I will add it.

Tofu is the carrier board recommended by Intergalaktik, the producers of the ULX4M. For early releases it is best to use the carrier board used by the ULX4M team.

Standard Raspberry Pi 40 pin GPIO header

Gigabit Ethernet port with PoE through the official Raspberry Pi PoE HAT

M.2 2242/3042 socket (key B) with micro SIM card holder. See compatibility list

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3x USB-A ports
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Full size HDMI port
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Camera and display ports (newer 22pin version, flexible adapter cables can be purchased separately here)

Two power inputs for industrial connectors (2.1mm barrel and standard 3.5mm terminal block)

Large input voltage range, from 7.5 to 28V. Also available on 3x1 header pins for sharing to HATs requiring higher voltages (recommended power rating: >24W)

Micro SD card slot. Only used for CM4Lite (no eMMC memory)

USB-C port to use it as an OTG device and for programming purposes. May also be used to power the CM4, with power constraints if used with peripherals

Circuit protections added for safety reasons (ESD, over- and reverse-current protections)

Standard Raspberry Pi, CM4 and 4 additional M3 mounting holes for design flexibility

Official Raspberry Pi Carrier Board The image is of the official Raspberry Pi carrier board.

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External power connector (+12V, +5V)
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2 x full-size HDMI® 2.0 connectors
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2 x USB 2.0 connectors, with header for two additional connectors

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Gigabit Ethernet RJ45 with PoE support
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Micro USB socket for updating Compute Module 4

MicroSD card socket for Compute Module 4 Lite (without eMMC) variants

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PCIe Gen 2 x1 socket
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Standard fan connector
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2 x MIPI DSI display FPC connectors (22-pin 0.5 mm pitch cable)

2 x MIPI CSI-2 camera FPC connectors (22-pin 0.5 mm pitch cable)

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Standard Raspberry Pi HAT connectors
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Real-time clock with battery socket and ability to wake Compute Module 4

Various jumpers to disable specific features, e.g. wireless connectivity, EEPROM writing

Or if all else fails, design your own carrier board in KiCad.

ULX4m Frame Buffer . View

ULX4M-LD is able to run 1080p video (1920 * 1080) @ 60 FPS using a frame buffer running on DDR3 at 800 transactions per second. VHDL code

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