Glasgow Embedded / Glasgow - History

revC2: save one BOM line by replacing 1k resistors with 2k2

revC2: move C13 and R3 (USB shield) a bit away from the usb-c connector

Allows easier experimenting with pin-in-paste for manufacturing.

revC2: separate current shunt for the INA233

The original idea in #165 and #135 was to reuse the 0.47 Ohms dropper resistor
we already have for the regulator as current shunt too. As the INA233 has a fixed
measurement range of +- 81.9 mV, this would allow to measure 174 mA. My initial
thought was that this is enough, as the specced load of the TPS73101 is 150 mA.

Review and experimentation has shown that the TPS73101 can be used to 350 mA in
most configurations before limiting set in, for a programmed output of 5 V I
could use it even up to 420 mA. As one of the design goals of using the INA233
is overcurrent protection, the settable range should be higher than what the
regulator can output in best case.

So the design is changed to a 0.15 Ohms current shunt and an additional 0.33 Ohms
dropper resistor in series. This gives a total 0.48 Ohms drop for the regulator
and a measurable current range to 546 mA.

For both resistors a DNPed parallel footprint is provided as before, allowing
the user to reduce the voltage drop if desired.

revC2: save one BOM line by replacing a 220k resistor against 2x 100k

revC2: simplify power sequencing

- The ice40HX does not need power sequencing (unlike the ice40UP5K in previous revs)
- Just the FX2 needs a proper reset circuit with delay after power on
- On a brownout on the 5V rail, not only the FX2 needs a reset, but also all ICs connected to the I2C bus
- Otherwise they could be stuck in a transaction
- Switch off the 3.3V whole rail with the MAX809J reset IC to solve this
- Reset the FX2 before the 3.3V rail becomes unstable

revC2: re-shuffle silkscreen labels ("Glasgow", creators, ports, OSHW, Sync) to work with the new TVS diodes

revC2: add symbol & footprint for new TVS diode array SP3012-06UTG

TODO: 3D model is just a placeholder, to be replaced with the correct one

revC2: fix & improve silkscreen

- improve Pu/Pd marking
- fix silkscreen pin numbering on the board edge
- fix silkscreen pin numbering for the pu/pd sections on the back side