

PicoMite 2X2 VGA Information
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This is a straightforward minimal PicoMite VGA setup, and is probably about as small as I can make it using a standard Pico and standard connectors (46mm x 50mm). It should be possible to panelize four of these on a single 100mm x 100mm PCB (you may have to specify 4mm side rails).

It incorpotates:
PS/2 keyboard input
VGA display output
Micro SD card socket
Power input vie the PicoMite USB connector or from an external source (pads beneath the PCB)..
WS2812B LED
GPIO connector includes:
. Three ADC pins
. Ten digital pins
. One customizable pin which can be VREF, RUN (the default) or GP15,
. 3V3 and GND.
NPX pads on bottom of board to extend Neopixel display. Will need external power with common ground.
SD card pads on bottom of board in same pattern as standard size SD card.

In order to keep the size down, all the resistors and diodes are surface mounted devices, however the resistors are size 1206 so they are quite manageable. The PicoMite is also surface mounted.

Assembly is fiddly due to the tight spacing, but shouldn't be too difficult if the following guidance is observed:

> Fit the 1N4148 diode (D2) first as it is tiny. The WS2812B should also be mounted at this stage.
> Fit all the resistors.
> Turn the board over and fit the SD card socket and D1 (if required)
> Turn it back and fit the PicoMite, soldering oposite corners first to keep it stable and aligned. It will overhang the PCB by about 0.5mm at each end. It's worth taking care to make sure positioning is correct right at the beginning as it will be very difficult to remove without damage later. It may help to support the board on blobs of blue-tack or smilar while doing this. 
> Fit C2 and the GPIO header
> Fit the two MOSFETs.
> Fit C1, the PS/2 and VGA sockets.



Bill Of Materials

1	PCB
1	U1 - Raspberry Pi Pico programmed with PicoMite firmware. No header pins!
1	U2 - WS2812B
1	Micro USB socket Molex 104031

1	K1 - 90 degree D9F 3-row VGA socket - short version (ebay - see pic))

1	K2 - PS/2 socket (ebay - see pic)
1	H1 - 8x2-pin male header pins or a female header. (Not a box header - not enough space)

1	C1 - 100nF ceramic capacitor.
1	C2 - 22uF electrolytic capacitor

1	R1 - 2R2
4	R2, R3, R4, R5 - 10k
2	R6, R9 - 270R
1	R7 - 820R
2	R8, R10 - 390R

1	D1 - 1A SMD (DO-214AC) Schottky diode 
1	D2 - SMD (SOD123) 1N4148
2	Q1, Q2 - VN10KN3-G or BS170. 2N7000 will usually work too. Note: fit BS170 "backwards".



Notes:

All resistors are size 1206 surface mount types.

D1 can be omitted if the external supply capability isn't required.

If pin A is linked to GP15 then it's drive capability will be slightly reduced if the WS2812B is fitted. It won't be possible to use the WS2812B in any sensible manner if GP15 is being used for something else.

R10 is normally recommended to be of any value between 200R and 500R.

D2 cannot be a Schottky type as the forward volt drop of a normal silicon diode is needed here.

C1 would probably be better if a tantalum electrolytic of at least 47uF or so were used but space is very restricted. If you have something that will fit then by all means use it.Another possibility is to fit a surface mounted capacitor underneath the PCB.
