So one of the things I plan to do when R-Pi are more available is to butcher a couple of them and incorporate some things I consider to be appropriate hardware fixes. This is my list so far, any feedback or additional suggestions welcome.
1. Remove the SD Card slot and replace it with a small adapter pcb containing a micro-sd connector. The full size SD card sticking out the end is ok for development or when you want to swap the card a lot, not so good when you want to build the whole Pi into something else and would like to use some of that dead space for other things. 1764377 micro-sd connector chosen, will be oriented at right angle to the current slot.
2. Replace usb polyfuse arrangement. Diodes Inc AP1212 seems to fit the bill. 1825303 33 pence each
3. Replace RG1 & RG2. Current plan is to use the TPS54231 1755637 as suggested by jamodio, however it's relatively expensive. Also looking at AP1533, 1825334 which appears similar from an external components point of view, but approx 1/10 the cost.
4. Cut the 1.8v from the Lan9512. Could do with the full gerbers to work out if this is possible. C29, C36 & C43 along with pins 15 & 38 just vanish into vias. Ideas welcome. My other options are to remove the Lan9512 and make myself a model A, or to leave RG1 off and see if we still boot with 1.8v from the lan9512 regulator.
5. As I'll be replacing the SD card slot, I'm contemplating if it's possible to add some power switching to allow running the slot at 1.8v to get some of the faster access modes. I think this will probably need some driver work and stealing a gpio from somewhere. I'd be tempted to use GPIO5 or GPIO27 (CAM_CLK, CAM_GPIO), but maybe the GPU will mess with those and GPIO31/CONFIG3 could be a better choice.
6. RTC based on MCP79410, 1823155
7. Removal of micro-usb power connector as I don't consider it appropriate. 5v and 3.3v can be supplied via P1 instead.
If only 1.8v was available on P1, some things could have been easier. So...
8. Replace P1 with a 28 pin connector to allow 1.8v to be made available. The extra two pins to extend off the end on the pcb and be wired to RG1's previous position.
9. For ease of integration, put P1 on the underside of the board and likely also replace P4 & S7 with headers allowing their connectors to be moved onto the underlying board and aligned better wrt case.
Thoughts ?
