PSPi 4 PCB 2 copy

Slight revision to the PSPi v4 board. This is a very rough work in progress. It's a total redesign with new schematics. The overall function will be the same to PCB 1.x, but the circuits are new. Changes include: - Improved battery charge detection. The board can detect how much amperage is being drawn from the battery during discharge, and can detect how much amperage is being provided to the battery during charge. This greatly improves the accuracy of the charge/discharge status. - No more pogo pins. The Pi will attach directly to the board, similarly to the attachment method of v3. The difference from v3 is that this board should have castellated holes that make the soldering process easier. - The LCD will shut off during reboots, preventing the appearance of a distorted image. - Better low-battery LED indication. No more blending of green and orange when the board is pulling a higher amperage. - Headphone board will be attached to the PCB, and will be breakaway. - Better audio filtering - Better power-on circuit. There will no longer be a condition where the system has to remain powered off for 3 seconds before powering it back on.