I'm in the process of building an OSD using the MAX7456 chip which uses the SPI port, and had a thought regarding the Chip Select pin. The shared PG2/PJ2 pin is close to the existing SPI/ISP header, but requires you to solder SJ2. Instead, why not give PG2 its own PTH connection between the SPI/ISP header and the shared PG2/PJ2 pin, and connect PJ2 directly to the existing shared PG2/PJ2 pin, eliminating the need for SJ2 (see attached sketch) APMV142.pdf. A ground pin could also be added to the APM as shown, but is not required to be passed through to the OilPan.
On the OilPan, a PTH is placed with no trace for PG2, just like the existing PG2/PJ2 shared PTH shown here:APMSV142.pdf. PG2 and PJ2 are now both available.
With these modifications, a 2x3 header could be plugged into the OilPan (rotated 90 degrees from the ISP pins) and connect to +5V, MISO, SCK and MOSI, along with the new GND and PG2 pin (for Chip Select). These modifications would maintain pin compatibility between different APM and OilPan revisions.
Thanks for listening,
Billy
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