Thanks guys for all the help, but I think I probably asked too vague a question (sorry, I'm not very good with electronics so I don't often know how to explain what I mean), what I meant was more: Can I connect the buttons in a matrix arrangement when I only have the one common ground wire?
My instincts tell me to try connecting GND to row 6 and VCC, P14
In Bu0836/A matrix - the common wire is related at individual ROW and not at all buttons/HAT possibles.
So you have a "common wires" for each ROW of matrix, in BU0836 mean six.
Ie. BU0836 ROW 6 is "common wire" to buttons 30, 32, HU, HR, HD, HL.
Notice that BU0836X is a different figure, since his matrix is integrated to circuit e this allow you
use one common wire to all buttons.In this
Saitek PCB the common wire (for buttons and HAT) is the pins PD0 and PD1
GND and VCC is only for LED. Not related to buttons or matrix.
I dont figure how light this LED - since you need VCC and GND to this, and mix this with rows and columns wires in SW2 probable is not good for BU0836 health...
If you can test with multimeter you see that VCC and GND is not connected to SW2. Only to LED and resistor (R28).
In
Saitek AV8R when you press SW2 (button 2) probable some relay or optocoupler in main circuit is closed and light (or blink?) the LED.
[/quote]but do you think it also work to desolder the diodes and reverse them,[/quote]
I remember that someone say that you can use diodes toward columns instead to rows - is case to make a test, so no desolder is need. Reverse then probable make HAT to stop to work.
[quote]remove the LED and resistor entirely and
put wires through where they were,[/quote
In case just ignore the LED, VCC and GND wires (remove these wires - Red and Black - from PCB).
Buttons and HAT dont make use of these two wires.
To hook SW2, SW3 and SW4 use:
BU0836 Columns 2, 3, 4 and ROW 1 - diodes 1N4148 toward ROW 1.
You save one wire if instead columns 2, 3, 4 use columns 3, 4, 5 since these already are use by HAT.
Sokol1