Dec 5, 2016

DieselPunk Cellphone - Walnut Case, Powered by Adafruit Feather Fona: Build, Part Two

The final build is layered - one thing on top of another. Work slowly and check frequently as you assemble! Once you start stacking things up, it will be difficult or impossible to fix a problem lower down in the stack.

First, let's take a quick look at how the FF aligns on the perma proto (pp) board with the SSD1306 OLED. The Smalls Perma Proto board connected holes are numbered 1-15 across its top.

When the FF is properly aligned on the perma proto (pp), the FF pin 2 will be at pp (perma proto) 14. PP 5 will then be at FF USB as in this photo:



We have to reroute some of the OLED connections to avoid using Pin 9 on the FF. That's the pin  used as the FONA RXD (data out from AVR to module). And, it's smack-dab in the center of the pin layout where the OLED connects. GND and +V also have to be rerouted on the perma proto board. 


How do we reroute on the perma proto board? Well, Lady Ada thought of that. You cut the traces on the back of the board, then reroute with jumper wires.

Notice, in the photo above, that the OLED pins occupy the top row of the perma proto board. The third row down is where the Feather Fona pins are soldered to the perma proto board. To jumper around the FF pins, cut traces between the second and third row with a hobby knifeWith a mulitmeter/continuity checker, make sure that the holes with cut traces are not connected. And that you have not cut traces by accident that should be connected.

Then, route jumper wires from the second row to its desired connection. The OLED connections that have to be rerouted are: GND, +V, DC, CLK and DATA. Do Not Cut traces, for the  OLED pins CS and RST. Those will connect directly to Feather Fona pins 11 and 10, respectively. 

When you get done rerouting the pins with jumper wires, your board should look like this:


Next, we'll assemble the LED Sequins. These are very small, and by themselves are hard to mount as backlights for the tiny microphone bezel. To make the LED Sequins easier to handle, cut a chunk of a second perma proto board with a Dremel or similar, with holes connected together in a 4x4 layout. Place the two Sequins on each end of the piece, making sure that +V is trace-connected. Likewise for GND. You can use 22AWG solid to solder these on, like so:


















Trim any excess wire leftover from mounting. Place the LED Sequins in the microphone cut-out and measure out a length (black and red) of 26 AWG solid, with some slack, to reach the bottom side of the perma proto at the GND/+V rails. When you're happy with that, solder the Sequin mount to the perma proto. It's a good idea to check these light up by applying power to the rails. You should be able to do this by just bending solid GND/+V wires into the rail holes and applying voltage. Don't glue the Sequins into the microphone bezel yet - we have to install the microphone before that, in a later step.

Finally, test mount the Jewel in the speaker bezel. Place the perma-proto on the OLED pins, aligning pp pin 5 with GND on the OLED. Measure and cut the wires for the Jewel so it just reaches the speaker bezel, with a little slack, and allow for stripping the wires for soldering. When good, solder the Jewel leads to the bottom of the perma proto, for GND/+V and FF pin 2/pp pin 14. 





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