Kit assembly

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This page is targeted towards people assembling from a SMD-ready kit - where all the SMD parts are attached and you only need to solder the through-hole parts and breakouts. There's also a page for SMD assembly, with some tips - you will want to use that if you're assembling from scratch.

If you get stuck or are unsure about something, feel free to ask for help on IRC (details on the wiki's frontpage).


Soldering order

The majority of through-hole parts need to be soldered in a particular order, assembling them in the wrong order will make the assembly significantly harder or even impossible in some situations.

These steps have to be completed in this exact order:

  • Expansion headers
  • 40-pin female header
  • 40-pin male header
  • 6-pin headers
  • Keypad
  • USB port
  • USB wires
  • Raspberry Pi Zero
  • Audio jack
  • GSM speaker
  • Display

These steps can be completed more-or-less at any time during the assembly:

  • GSM microphone
  • 18650 board JST header
  • 18650 board Velcro strip
  • TP4056 board
  • GSM modem
  • 5V DC-DC (step-up)
  • Vibromotor

Expansion headers (needs pictures)

There are 4 expansion headers on the back board - logically grouped in three groups (top, bottom and side headers).


  1. For each pin header:
    1. Insert the headers into the board so that they're on the top
    2. Solder one pin of the header
    3. Check the header alignment - tweak it if it's not aligned by reheating that pin and repositioning the header
    4. Solder the opposite pin of the header, align if necessary
    5. Solder the remaining pins

40-pin female header to front board


  1. Insert the 40-pin connector into the board from below. Your task is to make sure that the connector is well-aligned, as after the connector is soldered to the board, you can't realign it.
  2. Optional: to help with alignment of the connector, you can use pliers to bend some pins of the connector so that they're pressing the connector together with the board, essentially, making sure that the connector is flush with the board - and also make the connector harder to move in the holes, so that it doesn't rotate by a couple of degrees by accident.
  3. Solder some corner pins together (1 or 2, no more), then check that the header is still aligned with the board. If it is out of alignment, reheat these pins and rotate the connector.
  4. After you're done checking and fixing, solder all the remaining pins.
  • Step 1
  • Step 2
  • Step 3
  • Step 4
  • Step 5

40-pin male header to back board (TODO)



6-pin headers (needs pictures)


  1. Prepare 2x 6-pin male headers and 2x 6-pin female headers
  2. To make the alignment of the headers easier, you should plug the back and front boards together, so that the headers on the boards are mutually aligned no matter what
  3. On back board, you need to solder a female header near the GSM modem and a male header (with a spacer between plastic and PCB) near the USB port, both facing towards the front board
  4. On front board, you need to solder a male header (with a spacer between plastic and PCB) near the ATMega and a female header near the display, both facing towards the back board

Keypad to front board


  1. Using tin snips or cutters, make 2x 2-pin headers, 3x 3-pin headers and 1x 4-pin header. If you're attaching a keypad that uses the keypad GPIO, you need an additional 1-pin header for the GPIO pin - otherwise, it can be omitted.
  2. Using tin snips or cutters, trim the pin headers from one side so that both top and bottom metal parts have equal length.
  3. Put the front board on your desk / in your PCB holder with the top side upwards
  4. Put the pin headers into holes. Preferrably, with the non-cut side upwards.
  5. Seat the keypad board onto the headers - it should be parallel to the front board, and the outlines should match, we'll be checking further as we go.
  6. Solder the pin headers to pads on the keypad board. For each individual header, after soldering a single pin of it to the keypad PCB, check that there's no gap between the keypad PCB and header plastic - if there is, re-heat the solder joint and press them together until there's no gap. After you're done, you should have a keypad+headers combo.
  7. Flip the front board (together with the keypad), so that it's bottom side upwards. Solder a single pin of the keypad&header combo to the front board. Then, check the following steps (if anything's wrong, reheat the solder joint you just did and adjust the board until it's OK):
    1. the keypad is still parallel to the front board
    2. the keypad sits flush to the front board - there's no gaps between front board and pin header plastic, or pin header plastic and keypad board
    3. the keypad and front board outlines are still aligned
  8. Solder all the remaining pins. During soldering, check that there's no gaps between the front board and pin header plastic.
  • Step 1 and 2
  • Step 3 and 4
  • Step 5
  • Step 6

USB port (needs pictures)


  1. Insert the USB port into the holes
  2. Solder one of the shield pins
  3. Adjust the port as required, press it into the board or rotate it as required
  4. Solder the other shield pin, check the alignment
  5. Solder the 4 data pins

USB wires

You need to connect Pi Zero USB data lines (coming from the testpoints) to the back board - using two wires is the cheapest and most accessible way to do that.


  1. Prepare a wire that's approximately 25mm (1inch) long - strip it of its insulation
    1. If the wire is multi-strand, twist the strands so that they keep together. Can also tin the ends so that the wire doesn't get un-twisted while manipulating it
  2. Fold the wire in half so that it forms a "U" shape with 2mm (~0.1in) distance between two halves
  3. Cut the wire so that its ends are on the same level, tin the ends
  4. Add some solder to the Pi Zero USB port testpoints
  5. Put one end of the wire on one test point - preferrably, the one that's positioned closer to the shield
    1. Per "Important" section, check that the testpoint isn't accidentally bridged to the USB shield pins with solder
  6. Solder the other wire to the second testpoint
    1. Now, you should have a loop of wire connecting two USB data testpoints together
  7. Place the Pi Zero on the 40-pin header on the back board while putting the wire loop through the hole on the back board
    1. Now, you need to solder the data pins to the back board
  8. Fold the two wires onto the testpoints so that they're more-or-less flush with the board
  9. Cut the loop so that there's only ~2mm (0.1in) of wire on the testpoints
  10. Solder the wire ends to the testpoints
  • Step 1
  • Step 4
  • Step 6
  • Step 9
  • End result

Pi Zero (TODO)



Audio jack (needs pictures)


  1. Insert the audio jack into the front board holes
  2. Solder it to the board

GSM speaker (needs pictures)

  1. Tin the speaker-side pads a little bit, depending on the location where your speaker model has pins. Don't make a solder blob, just a small thin layer of solder.
  2. Put a small drop of superglue on the center of the speaker adapter PCB
  3. Press the speaker onto the PCB until it's glued to the PCB (can use a clothespin to hold it for some time, even leave it there while soldering the speaker to the adapter)
  4. Solder one pin of the speaker to the PCB (stay away from possible superglue fumes)
  5. Solder the other pin of the speaker to the PCB
  6. Tin the pads on the bottom of the speaker adapter a little bit (don't leave a large solder blob)
  7. Put the speaker adapter with the speaker into the slot on the front board (so that the pads match)
  8. Solder one of the speaker adapter pads to the front board pad
  9. Solder the other pad to the front board

Display (needs pictures)


  1. Cover the solder jumper header holes on the top with Kapton/other tape
  2. Shorten the display pin header pins - they only need to be ~2mm (~0.1in) long
  3. Insert the display pins into the holes on the top
  4. Solder one display pin to the board
  5. Align the display so that it's parallel to the board
  6. Solder the remaining pins
  7. Set the solder jumpers correctly, according to the pinout of the display you have

GSM microphone (needs pictures)


  1. Insert the microphone into the holes in correct polarity
  2. Solder the 1st pin
  3. Align the microphone
  4. Solder the second pin

18650 board JST wire (TODO)

Kapton tape and hot glue applied to the 18650 holder board

It's advised to apply a blob of hot glue on the place where battery wires are soldered to the 18650 board.

18650 board Velcro (TODO)

Velcro added to both back and 18650 boards

Currently, there's nothing that holds the battery holder and back board together, apart from the battery cable. An easy non-permanent solution is Velcro (you need to get the kind that has glue on both sides). Just cut the Velcro pieces into approx. 30mm*10mm pieces and attach them to the 18650 board and back board.

TP4056 board (needs pictures)


  1. Place a small blob of solder on the IN+ pin
  2. Put the TP4056 board on the back board
  3. Solder the IN+ pin of the TP4056 board to the back board
  4. Align the board if necessary
  5. Solder the IN- pin
  6. Solder the OUT+ and B+ pins
  7. Solder the B- pin
  8. Solder the OUT- pin

GSM modem (2G) (WIP)


  1. Using tin snips or cutters, make one 6-pin male header and one 5-pin male header
  2. Place the back board on the desk so that its top side is upwards
  3. Insert the pin headers into the back board, pointing the long ends upwards (inserting the short ends into the holes)
  4. Put the spacers onto the pins
  5. With the 5-pin side, you do not need to connect the ANT pin, and you also need to position the 6-pin spacer so that it doesn't overlap with the ANT pin
  6. Put the modem onto the pins (SIM card slot upwards, SIM card opening facing the outside of the board)

5V DC-DC (needs pictures)

  1. Twist the USB port shield tabs off the DC-DC board with pliers
  2. Heat all 4 pins of the USB port with a soldering iron at the same time, once the solder's melted, remove the port from the board
  3. Wet the "DC-DC input" holes on the back board (on the TP4056 side) with solder, but not too much (so the DC-DC board is still flush to the back board)
  4. Put the DC-DC board onto the back board
  5. Solder the positive (non-GND) input pin to the back board
  6. Check the alignment, realign the board while reheating the first pin, if necessary
  7. Solder the second input pin (GND)
  8. Solder the output pins to the back board, using pieces of wire or pin header pins
  9. Wet the back board "DC-DC output" pads (on the USB port side) with solder
  10. Solder the wires/pins to the DC-DC board pins on the output side
  11. Add solder blobs to connect back board pads to the wires/pins
  • End result

Vibromotor (needs pictures)


  1. Shorten the vibromotor wires so that they're ~2cm (~0.7in) long
  2. Remove insulation from the wire ends so that ~2mm (~0.1in) of wire is exposed
  3. Position the vibromotor in a way where you can solder it to the diode pads
  4. Glue the vibromotor to the front board
  5. Solder the vibromotor wires to the diode pads