PiBoy-Zero

link: https://oshpark.com/shared_projects/1p90FvAB

waiting for the pcb to be fabbed and the ordered parts to arrive :-D

meanwhile: just created a repo on github with the current schematics here: https://github.com/JohSchneider/piboy-zero

first version of the schematic and layout for the carrier-pcb - kicad does a nice job rendering it :-)

front side:

back side:

of battery + powerboost + softpower-circuit

the breakoutboard is a cheapish chinese import, with a slightly different wiring for the backlight - the important part: the display is the same as in adafruits 2.2" pitft hat (and their 2.2" spi display breakout).

hence it is easy to get it up and running following these instructions:

https://learn.adafruit.com/adafruit-2-2-pitft-hat-320-240-primary-display-for-raspberry-pi/easy-install

this time more internal components (on the raspberry and the powerboost pcb) have been taken into consideration while positioning the battery and resizing the enclosure - the new boundingbox measures 106mm x 48.3mm x 21mm

also the (preliminary?) position/cutouts for the usb and headphone jack have been included.

and lastly: shoulder buttons!

breadboard prototyping of the powerboost + battery + soft-power-button circuitry

off (powerboost enable pulled low)

on touch of the push-button -> power on!

the three wires running to the top and out the image will be connected to the raspberry pi, and give it +5V, Gnd and a control/sense wire to the soft-power circuit - that way it will be able so detect further button pushes shutdown properly and cut the power by pulling the control-wire low

further description of the soft-power circuit is available here:

http://www.mosaic-industries.com/embedded-systems/microcontroller-projects/raspberry-pi/on-off-power-controller

ugly&boring version of a 3d-printable case for the whole assembly :-P

after moving components around a bit, and adding a 1200mAh battery...

the current bounding-box measures: 104mm x 46mm x 17mm

(this *will* change, since currently the various components on the pcbs are not factored in)

after studying the schematics, board-layouts and parts-lists of the different adafruit powerboosts it became clear that keeping the whole project hand-solderable would be tough - considering that the powerboosts are build around a boost-converter (and sometimes a lipo-charger) that only comes in a QFN-package - which seems like too much of a hassle to solder without access to a reflow setup :-(

so plan-B might be to integrate the circuit as an as-is module, with (wire-)bridges from the carrier-pcb to the powerboost-pcb?

like this maybe?

let there be sound!

https://learn.adafruit.com/introducing-the-raspberry-pi-zero/audio-outputs - either the simple variant with few resistors or the raspberry-B+ version with buffer-IC

an I2S-DAC like variant is most likely overkill.. like the

https://shop.pimoroni.com/products/phat-dac ( https://www.adafruit.com/product/3016 IC=PCM5102A )

or similar https://polyvection.com/shop/plaindac/ (IC=PCM5142)

a dedicated button to power the whole thing on and off (in an orderly fashion) might be nice - something like this:

http://www.mosaic-industries.com/embedded-systems/microcontroller-projects/raspberry-pi/on-off-power-controller