|
Caution
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This design is currently a work-in-progress and undergoing major revisions. |
This directory contains the hacker version of the Tomu FPGA. 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. Additionally, it has fewer power regulation components, which may impact stability.
|
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 |
|
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 |
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.
Building a jig is hard if you do not have maker tools readily available. But there is another way to make a poor man’s programmer for fomu. Not rock solid, but it works.
You have to make seven cables like this, with a DuPont female and and a probe on the other end. Basically, you behead one end of a DuPont cable, strip a little bit of the cable and solder a probe. My soldering is terrible, but you do not need fine art here.
Then you connect the cables to the Raspberry and try to fit the probes on the fomu. The space is not much, but it is possible. I suggest to start from R and going clockwise. Leave G and V as the last ones. G tends to snap away quite easily, but it is also available on the other side, on the button pad. I is rather difficult too, because the board is really crowded there, but (with my probes, at least) it is possible to touch it just enough to have the contact done.
The pinout is the one above, that has to be matched with the Raspberry pinout in fomu-flash.
V should be connected to 3.3V, not 5V. Once everything is connected,
you can run fomu-flash. Be sure to verify the bitstream with -v,
because of course the connection is quite brittle.
Have fun!