~hp/chimaera_dsp_unit

3.3V version of Revision 4
path fixes after repo split
add READMe.md and licensing
solder paste clearence for 125um mylar stencils
EDA: add missing Digi-Key part numbers
AD75019 Rev2. case exploded labels.
equal length traces for differential ethernet lanes
EDA: all resistors now in 0603 format
chimaera case: adaptions for board design revision 4
bug-fix in DSP with wrongly wired I2C2
polished W5500 integration, add AD75019