vt1200/reference/keyboard-mouse/lk201emu/doc/kicad.md

Digital Equipment LK201 keyboard emulators

The kicad subdirectory contains two subdirectories, lk201 for the USB emulator and lk201ps2 for the PS2 version. In both you will find the design files for the emulator circuit board, which you can inspect or modify using the open source KiCAD package.

Creating the circuit board

There are three ways to get a circuit board.

1. From the shared designs section of the OSHPark PCB fabricator website. You will there both the USB board and the PS2 board.
2. From any PCB fabricator that accepts KiCAD board files (such as OSHPark).
3. From any PCB fabricator that doesn't, by generating the standard Gerber files.

If you want to use a fabricator that needs Gerber files, open the lk201.kicad_pcb (USB) or lk201ps2.kicad_pcb (PS2) file using KiCAD (specifically the Pcbnew application) and use the File->Plot menu option to generate them. You'll want to review the detailed instructions from the fabricator to confirm settings, file name rules, etc.

Schematic

The board schematic is in lk201.sch (USB) or lk201ps2.sch. You won't need this to create the board, but you can review this if you are interested, or if you want to modify the design.

Assembly

The design is a simple circuit board with all through-hole components. If you have experience building small electronic kits it should not create any problems. If you do not, you may want to seek out some help since this is not a "Heathkit" style kit with detailed instructions or tutorials.

USB board

Parts list

Here are all the parts in the design, with schematic reference (also on the board silk screen labeling), value or device type, description, along with manufacturer name and Digikey part number. The Digikey numbers are just by way of illustration. Capacitors and resistors are generic, you can replace them by similar devices from other suppliers so long as they fit in the available space. The capacitors are small ceramic devices with 0.1 inch lead spacing; the resistors are standard 1/4 watt parts. The transistor is a general purpose small NPN transistor, many other TO92 package transistors should work so long as the pinout matches. Beware of the 2N2222, there are two variants with different pinouts!

If you don't want the key click and beep (bell) features, omit LS1, Q1, R1 and R2.

Ref	Value	Description	Manufacturer	Digikey part #
C1	0.1uF	Unpolarized capacitor	Kemet	399-14010-1-ND
C2	0.1uF	Unpolarized capacitor	Kemet	399-14010-1-ND
C3	0.1uF	Unpolarized capacitor	Kemet	399-14010-1-ND
C4	0.1uF	Unpolarized capacitor	Kemet	399-14010-1-ND
C5	0.1uF	Unpolarized capacitor	Kemet	399-14010-1-ND
C6	0.1uF	Unpolarized capacitor	Kemet	399-14010-1-ND
C7	0.1uF	Unpolarized capacitor	Kemet	399-14010-1-ND
J1	RJ22	RJ connector, 4P4C (4 positions 4 connected), RJ9/RJ10/RJ22	Assmann WSW	AE10381-ND
LS1	PS1420	Crystal speaker/transducer	TDK Corporation	445-2526-1-ND
Q1	2N3904	0.2A Ic, 40V Vce, Small Signal NPN Transistor, TO-92	ON Semiconductor	2N3904FS-ND
R1	1k	Resistor, 1/4 W	Stackpole	CF14JT1K00CT-ND
R2	3.3k	Resistor, 1/4 W	Stackpole	CF14JT3K30TR-ND
U1	L78L05	Positive 100mA 30V Linear Regulator, Fixed Output 5V, TO-92	ST Microelectronics	497-13127-1-ND
U2	Trinket M0	Adafruit Trinket M0 board (SAMD21)	Adafruit	1528-2361-ND
U3	ICL3232CPZ	Dual RS232 driver/receiver, 5V supply	Renesas	ICL3232CPZ-ND

If you want to use Digikey as your supplier, the saved BOM is available there.

If you need alternate sources for various components, that should be no problem so long as the pinouts match. For example, the MAX3232EPE transceiver has been reported as a valid alternative for U3.

Assembly suggestions

I found that this order of installing the components works well:

1. U3 (16 pin DIP)
2. Resistors and capacitors
3. U1 (voltage regular) and Q1 (transistor)
4. LS1 (piezo beeper)
5. U2 (Trinket M0). The board comes with a set of pins. Cut off two 5-pin sections and solder these to the board, then slip the Trinket onto the pins and solder it.
6. J1 (RJ connector)

Note the correct orientation of U1, U2, U3, and Q1.

PS2 board

Parts list

Here are all the parts in the design, with schematic reference (also on the board silk screen labeling), value or device type, description, along with manufacturer name and Digikey part number. The Digikey numbers are just by way of illustration. Capacitors and resistor are generic, you can replace them by similar devices from other suppliers so long as they fit in the available space. The capacitors are small ceramic devices with 0.1 inch lead spacing; the resistors are standard 1/4 watt parts.

If you don't want the key click and beep (bell) features, omit LS1 and R1.

Ref	Value	Description	Manufacturer	Digikey part #
C1	0.1uF	Unpolarized capacitor	Kemet	399-14010-1-ND
C2	0.01uF	Unpolarized capacitor	Kemet	399-4150-1-ND
C3	0.1uF	Unpolarized capacitor	Kemet	399-14010-1-ND
C4	0.1uF	Unpolarized capacitor	Kemet	399-14010-1-ND
C5	0.1uF	Unpolarized capacitor	Kemet	399-14010-1-ND
C6	0.1uF	Unpolarized capacitor	Kemet	399-14010-1-ND
J1	RJ22	RJ connector, 4P4C (4 positions 4 connected), RJ9/RJ10/RJ22	Assmann WSW	AE10381-ND
J2	Mini-DIN-6	6-pin Mini-DIN connector	Adam Tech	2057-MDJ-006-FS-ND
LS1	PS1420	Crystal speaker/transducer	TDK Corporation	445-2526-1-ND
R1	3.3k	Resistor, 1/4 W	Stackpole	CF14JT3K30TR-ND
U1	L78L05	Positive 100mA 30V Linear Regulator, Fixed Output 5V, TO-92	ST Microelectronics	497-13127-1-ND
U1	Itsy Bitsy (5V)	Adafruit Itsy Bitsy board, 5V version	Adafruit	1528-2501-ND
U2	ICL3232CPZ	Dual RS232 driver/receiver, 5V supply	Renesas	ICL3232CPZ-ND

Warning: there are two versions of the Itsy Bitsy, as there are with many of the AVR based Arduino microcontrollers. One has 3.3 volt I/O, the other has 5 volt I/O. The PS2 design requires the 5 volt version. Do not use the 3.3 volt version, it will be destroyed when you plug in the DEC side serial cable since that supplies 12 volts to the board and the 3.3 volt Arduino has a regulator that can only handle 6 volt max power input. And even if the regulator could handle it, driving a PS2 keyboard with 3.3 volt logic levels will not work.

If you want to use Digikey as your supplier, the saved BOM is available there.

Assembly suggestions

I found that this order of installing the components works well:

1. U2 (16 pin DIP)
2. Resistor and capacitors
3. LS1 (piezo beeper)
4. U1 (Arduino). The board comes with a set of pins. Cut off two 14-pin sections and a 5-pin section and solder these to the board, then slip the Itsy Bitsy onto the pins and solder it.
5. J1 (RJ) and J2 (mini-DIN) connectors.

Note the correct orientation of U1 and U2.

Software load

After the board is built you will need to load the software. See the software.md file for instructions.