Introduction: Bluetooth50g - ​an Upcycle Project for a Broken HP50G Calculator.

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The conducting paths to the display are broken due battery leaking.
Batterie leaked and corroded the paths. The calculator for itself works, but the results are not shown on the screen (only vertical lines).

The system emulates a bluetooth keyboard and was tested on:

* EMU48 on Android and

* EMU48 on Windows 10.

A vibrating motor is installed for haptic feedback:

* after pressing a key

* missing Bluetooth connection (3x long vibs)

Step 1: Electronic Parts Needed

Following parts were used:

* Adafruit Feather nRF52 Bluefruit LE - nRF52832 Bluetooth Low Energy AF3406

* battery (see requirements inside adafruit manual)

* optocoupler ex. FOD852

* vibrating motor

* shrinkable isolating tubes

* resistances: 150, 220, 2200, 47000 Ohm

* power switch

* jumpers

* insulated wires

Step 2: Interrupting the USB-Power

I interrupted the power from the normal USB port to prevent unattended loading of the battery.

The TX pin is need to catch the information of the UART.

The battery was connected to a different contact ("USB" pin near battery pins) on the motherboard.

Step 3: Preparing the Adafruit Board

The bluetooth module can reset itselfs and/or the calculator.

Step 4: General Power Switch

Coin battery (as shown) is not needed (connection cables habe been removed).

I installed a general power switch to deconnect from battery.

The three jumpers are used to measure the currency for the vib, calculator, adafruit module.

Step 5: ...full Mounted - Ready for Clousing

Insert the isolating layer to prevent short circuits while mounting the two halves.

Mount isolating tape on the top side of the bluetooth circuit.

Step 6: Resources for the Bluetooth50G

The programm is still under development.

The last files can be found under:

https://drive.google.com/drive/folders/1XtnE-HOCTl...

"KEY ," (COMMA) is used for the SPC - to work on ANDROID

Scancode 188 # ,
Map 188 104 # SPC
End

Step 7: Special Thank Goes to

Special thanks to:

EMU48: Christoph Giesselink

Emu48 for Android: Régis Cosnier: for supporting me with the keyboard

comp.sys.hp48 group

https://www.hpmuseum.org/forum/