Great thanks to RB!
c6100/c6145/c5220 mezzanine slot pinout (analyzing...)
side1,g,12V,12V,g,3.3V,3.3V,3.3V,3.3V,3.3Vaux,g,NSOp0,HSOn0,g,g,HSOp1,HSOn1,g,g,HSOp2,HSOn2,g,g,HSOp3,HSOn3,g,g,nc,key,g,HSOp4?,HSOn4?,g,g,HSOp5?,HSOn5?,g,g,NSOp6?,HSOn6?,g,g,HSOp7?,HSOn7?,g,g,refclk-,refclk+,g,RST,R13,R12
side2,g,12V,12V,g,3.3V,3.3V,3.3V,3.3V,g,nc,g,g,HSIp0,HSIn0,g,g,HSIp1,HSIn1,g,g,HSIp2,HSIn2,g,g,HSIp3,HSIn3,g,key,nc,g,g,HSIp4?,HSIn4?,g,g,HSIp5?,HSIn5?,g,g,HSIp6?,HSIn6?,g,g,HSIp7?,HSIn7?,g,g,R11,g,WaKe,R8