Tomu, I’m (FPGA version)

I’m Tomu FPGA (Fomu for short!) a tiny FPGA board which fits in your USB port. People sometimes call me "Fomu" for short!

I have two buttons and an RBG LED.

Telling Tomu and Tomu FPGA apart!

Professionally produced Tomu boards have the following color scheme; * Tomu FPGA boards are blue. * Original Tomu boards are green.

However, as people are encouraged to produce their own Tomu boards, please look at the device careful to check what type you have. See the following table for what to look for;

	Original Tomu	Tomu FPGA
Board Color	Green	Blue
LEDs	One Green + One Red	One Red Green Blue LED
Components	A single large black IC taking up most of the board.	Multiple little black ICs covering the board.
Test point pattern	FIXME	FIXME

The original Tomu has one large black IC on the board.

Contact

• Announcement mailing list - Low traffic list for announcements.

• Discussion mailing list - List for discussing development / new features / etc.

• IRC Channel - irc://irc.freenode.net/#tomu - IRC channel for discussing anything related to the project.

Board Details

There are currently two versions of Tomu FPGA. Both boards and based around mostly the same schematic and should be mostly compatible and based around the Lattice iCE40UP5K FPGA and have the same set of features listed below;

• Lattice iCE40 UltraPlus 5K

  • 5K 4 input LUTs + DSP tiles

  • 128 kilobytes internal SRAM

  • 1024 kilobytes (or more) flash (XIP possible)

• 1 x RGB LED

• 2 x touch buttons

Hacker version

• The hacker version is designed for people who are up to the challenge of building their own board.

• It has a simpler PCB which makes it cheaper to produce in a small quantities.

• However, it uses a non-standard footprint for the FPGA WSCP which reduces yield and long term reliability making it unsuitable for mass production.

PCB Specification

Caution

This PCB specification is currently a work-in-progress.

Board Size	0.37 x 0.51 inches (9.5 x 13.1mm)
Board thickness	0.6mm
Number of Layers	2
Components	Single Side
Silkscreen	None, one side or all sides is fine.
Number of through holes	0
Minimum trace width and clearance	4mil traces, 4mil clearance
Vias + Drills	0.2mm via drills with 0.5mm annular rings
Smallest pitch size	0201 resistors, WCSP parts
Control Impedance	Not required
Solder Mask color	Blue
Plating	ENIG
Material	FR4

Programming jig

V	Vcc	0.000 x 0.275 in
S	SPI_CS	0.000 x 0.160 in
C	SPI_CLK	0.000 x 0.0825 in
I	SPI_MISO	0.027 x 0.000 in
O	SPI_MOSI	0.100 x 0.000 in
R	RESET	0.170 x 0.000 in
G	GND	0.302 x 0.0000 in

Laser cut SVG for the programming jig for use with fomu-flash tools. The pinout works for both the Pi 2 and Pi 3.

Production version

• The production version is designed for mass production.

• It uses advanced PCB technologies like laser drilled and blind vias.

• You get a production version if you order from Sean \'xobs' Cross through or after the Crowd Supply campaign.

PCB Specification

Caution

This PCB specification is currently a work-in-progress.

Board Size	0.37 x 0.51 inches (9.5 x 13.1mm)
Board thickness	0.6mm
Number of Layers	4
Components	Single Side
Silkscreen	Both
Number of through holes	0
Minimum trace width and clearance	0.1mm track width, minimum clearance is 0.1mm
Vias + Drills	Between layers 1 and 2 - Laser-drilled - 0.2mm/0.1mm blind vias Between layers 3 and 4 - Laser-drilled - 0.2mm/0.1mm blind vias Between layers 2 and 3 - Mechanical - 0.5mm/0.2mm buried vias
Smallest pitch size	0201 resistors, WCSP parts
Control Impedance	Not required
Solder Mask color	Not-green
Plating	ENIG on the top. Hard gold on the fingers on the underside. Hard gold on the edge of the top.
Material	FR4

Development Firmware

The Lattice iCE40UP5K has a fully open source Verilog → Bitstream toolchain.

Supported by the LiteX BuildEnv. The LiteX BuildEnv supports your choice of CPU architecture;

• LatticeMico32

• RISC-V - PicoRV32

• RISC-V - VexRISCV

As the board is supported by the LiteX BuildEnv, you can developed;

• Bare Metal C Firmware

• Zephyr RTOS

• MicroPython (FuPy)

License

The contents of this repository excluding third_party folder is released under your choice of the following two licences:

• the "Creative Commons Attribution-ShareAlike 4.0 International License" (CC BY-SA 4.0) full text of this license is included in the LICENSE file and a copy can also be found at http://creativecommons.org/licenses/by-sa/4.0/

• the "TAPR Open Hardware License" full text of this license is included in the LICENSE.TAPR file and a copy can also be found at http://www.tapr.org/OHL