Instructions | 4TH Calculator

1

Cut the perfboard

Cut the perfboard to 2" x 3.5" (50 x 89 mm) dimension or 20 x 35 pads.
2

Solder push buttons

Solder the 35 push buttons to the perfboard top layer. Each button is in the middle of 4 x 3 pads, the grid is 0.4".
3

Wire the buttons

Wire the buttons to columns and rows on the perfboard bottom layer. Build a keyboard matrix without diodes. Pullups are integrated in the MCU.
4

Mount the dongle

Remove the USB connector from the dongle.
Glue (hot glue, mounting tape) the dongle to the perfboard bottom layer, upper left corner.
If you do not want to use the BLE, cut off the BLE antenna.
5

Mount USB Breakout

Glue (hot glue, mounting tape) the USB Breakout or the Adafruit Micro-Lipo Charger to the perfboard bottom layer.

Wire the buttons to the dongle

Wire the button rows and columns to the dongle.

Description	Dongle	Function	Calculator
PB3	CN1.5	SWO	ROW0
PB2	CN1.7		ROW1
PA6	CN1.9	D12	ROW2
PA7	CN1.10	D11	ROW3
PB6	CN2.6	UARTRX	ROW4
PA9	CN2.7	D9	ROW5
PA8	CN2.8	D6	ROW6
PA0	CN2.3	A3	COL0
PA1	CN2.10	A2	COL1
PA2	CN2.4	D1	COL2
PA3	CN2.5	D0	COL3
PA5	CN1.8	D13	COL4

7

Wire the JTAG SWD (optional)

Only needed if you want to debug the board.
Description Dongle Function JTAG 10pin
GND CN1.1 GND 3, 5, 9
NRST CN1.2 RES 10
PA13 CN1.3 SWDIO 2
PA14 CN1.4 SWDCLK 4
3V3 CN1.6 3V3 1
8

Place the Diodes (optional)

I use a BAT54C double schottky diode in SOT23 package. Solder the diode to the perfboard bottom layer.

You can also use two 1N4148 diodes.
9

Wire the USB connector

USB breakout without charger:
10

Mount the OLED Display

Solder or glue the OLED Display to the perfboard top layer.

Description	Dongle	Function	JTAG 10pin
GND	CN1.1	GND	3, 5, 9
NRST	CN1.2	RES	10
PA13	CN1.3	SWDIO	2
PA14	CN1.4	SWDCLK	4
3V3	CN1.6	3V3	1

4TH Calculator