Final list of materials:
Raspberry Pi 3 Model B
MicroSD Card (32GB)
Adafruit PiTFT 3.5” PLUS Touchscreen
Lithium-Ion Polymer Battery (1200mAh)
Wireless Bluetooth Keyboard
5.5V to 3.3V step down converter
Adafruit Powerboost 1000c
Female USB Connectors
Male USB Connectors
MicroUSB POWER ONLY Cord (short)
Wifi Adapter (optional)
2x 3mm LEDs
2x 200ohm resistors
A 3D Printed case OR hack your own out of hard drive cases
pliers (round nose)
hookup wire (stranded recommended)
hot glue gun + glue
(opt) helping hands
Before assembling anything, I had to get the Pi3 to boot with the Adafruit PiTFT plus, which was a pain in the butt. The adafruit website declared,
“The display uses the hardware SPI pins (SCK, MOSI, MISO, CE0, CE1) as well as GPIO #25 and #24. GPIO #18 can be used to PWM dim the backlight if you like. All other GPIO are unused.”
I found that to be false info. I scratched my head trying to figure out how to find which pins were being used and which ones weren’t, and I came up with the brilliant and monotonous idea of connecting 40 jumper wires from the PiTFT to the Pi 3. I disconnected each pin one at a time to see if it would boot correctly, then removed the jumper wire if it wasn’t needed. In thirty minutes, I had the right pins to get the Pi to boot onto the TFT.
Using the chart above helped a lot (credit to whoever’s chart it is), and here are the GPIO pin numbers I came up with, and their functions:
pin 1 - 3.3V PWR
pin 2 - 5V PWR
pin 9 - GND
pin 18 - GPIO24 (GPIO_GEN5)
pin 19 - GPIO10 (SPI0_MOSI)
pin 21 - GPIO9 (SPI0_MISO)
pin 22 - GPIO25 (GPIO_GEN6)
pin 23 - GPIO11 (SPI0-_CLK)
pin 24 - GPIO8 (SPI_CE0_N)
pin 26 - GPIO7 (SPI_CE1_N)
pin 27 - ID_SD (I2C EEPROM)
pin 28 - ID_SC (I2C EEPROM)
I had to wait three to four days for the case to finish drying, but boy, was it worth it!
I started by desoldering the Li-Po battery from the inside of the bluetooth keyboard, attaching to the leads the 5.5V to 3.3V step down converter.
The Vout of the step down I soldered go to the 5V and GND through-holes on the Adafruit Powerboost 1000c.
I left the original USB port on the adafruit powerboost and permanently soldered it to the board.
I figured it would be easier to use a well off microUSB cord than to play around with making my own with hookup wire. Fortunately, I had an older (and shorter) microUSB cord that was just for power, not data transfer, so I used that. I wasn’t able to fit the microUSB cord through the holes in the case, so I stripped off the plastic cover to reveal the wires, and I soldered those onto the Pi. I checked with a multimeter which pads were 5V and GND, so I knew where to solder.
In the end, I decided to forget attempting to get 12 hookup wires through the holes in the case, and I resoldered a 2x20 GPIO header onto the Pi and connected the PiTFT on top of those (like it was intended to be used).
In the case, I drilled two holes for a power light and a low battery light. All of these I soldered from the adafruit powerboost, so I rigged up my 3mm LEDs.
** **I wrapped a 200ohm resistor around the stripped wire, soldered the two joints, then trimmed the wires.
I accidentally burned out an LED before realizing that the resistor was in parallel, therefore not allowing the full resistance to get to the LED. I trimmed the wire after that. (below)
** **My solder joints are pretty ugly, I know. But I promise I made them nicer! I also covered that part of the wire in electrical tape.
Next was to solder hookup wire to the male USBs:
I made each one a different length, since the female USBs were different lengths away.
**Hot gluing the solder joints was a life saver for me, because if you bent the connections/wires too much the joints would break off. **
After putting each USB in, I had to bend and twist the wires so the Raspberry Pi and PiTFT still fit snugly in the case, with the wires bent around it.** **
I soldered the 3 green wires to the Vs, EN, and GND through-holes and connected them to the power switch (not shown). The USB cable soldered to the pi I plugged into the socket, and in the top right hand corner I used a multimeter to find the polarities of the Low Battery LED pads, and soldered one of the 3mm LEDs to that.
Under that swarm of wires I placed the LiPo battery and taped it to the bottom with electrical tape.
Soon after, all I had to do was plug in the LiPo to the Powerboost 1000c, put the bevels in place, and watch the magic happen (the tape is on the top because I haven’t decided on a good way to secure the bevel yet).
Viola!! My very own portable linux computer. SO EXCITED!!
And yes, that is Doctor Strange as my background. ;)
I’m feeling very accomplished about this, and I hope this walk-through has entertained you or inspired you to make one of your own. If you have any questions about things I did, don’t hesitate to contact me!
Until next time.