[rescue] SBusFPGA V1.3

[Romain Dolbeau]

Hello,

I finally decided to do a V1.3 of the SBusFPGA, using the same FPGA 
board as in previous version, but rerouting everything much more cleanly 
and replacing the micro-sd by a HDMI connector. All components (but the 
SBus connector itself) are now top-side.

I also switched supplier from SeeedStudio to JLCPCB for everything but 
the main 3 board-to-board connectors (SBus plus the pair of 2x32 2.54mm 
headers).

This makes the custom carrier a lot less expensive to manufacture! Cost 
was slightly below $190 for 5 carriers shipped to France, plus the need 
for about 9€ worth of B2B connectors per board - but you need to order a 
lot of stuff from Mouser to avoid paying high shipping cost... and 
solder the 224 pins by hand.

Accelerated framebuffer seems to work fine, now in gorgeous 1920x1080, 
24-bits using the builtin HDMI connector. Looks better than the 
2-bits-per-channel VGA resistor ladder :-)

However something has broken USB at some point, driver recognizes the 
controller but not the device. There were update to Litex in the 
meantime, I'll have to figure out what broke...

I2C temperature control is fine. I also added a small plug on the I2C 
bus, meant to be compatible with the 'qwicc' standard from SparkFu. So 
it should be possible to wire extra sensors to control the environment 
in other parts of the machine. Could be useful when running pairs of 
SM81 or SM512 :-)

I still need to update the 3D-printed extension for the board to sit 
properly in the SS20.

It's all on GitHub: <https://github.com/rdolbeau/SBusFPGA>, merged on 
'main'.

Cordially,

-- 
Romain