PCB modification

Alexander Rhodes · Jun 27, 2011

Printed circuit boards, my worst nightmare, I need some help here and didn't know where to post, hope I got the right area.

But here's my problem, I need to modify a PCB for the wheel of a Thrustmaster RGT pro clutch to fit my new wheel, and I can't figure out how they wired it together and what they use the resistors for.

Heres a pic:

Am I correct in thinking they mounted everything in a serial formation and used the resistors for the miniprocessor to tell which button was pressed? And if so, does that leave me unable to cut move and re-solder buttons into a new formation?

The board it connects to is here (connectors are bottom left corner)

There are also 9 holes unused on the board, to 4's and 1 single, (J4 J3 and TP1(on the main board I havean unused TP1 J3 is To Pedal_2 and J4 is To Paddle(axis))) could anyone explain what these are able to connect to, or where they meant to be push-pull plugs like the main board?

Also the question arises, if I can't relocate the buttons, I'll need to ditch the whole board, and if so, will I be able to connect my paddle shifters straight to the main board?

At the very least I need my paddle shifters, the buttons can always wait till a later date.

Thanks in advance guys

Brian Clancy · Jun 27, 2011

To be honest Alexander, I would ditch that in favour of a BU0836 USB input board from Leo Bodnar http://www.leobodnar.com/products/BU0836/ inexpensive, easy and very powerful

It will do everything you want

Alexander Rhodes · Jun 27, 2011

Thanks for the reply Brian,
The problem is I don't have the cash to spare on one yet. Although I'll be ordering an Sli-Pro for the buttons and paddles (and display) eventually, but that wont be for another month, and then delivery on top too lol. I was thinking about also ordering the 12 bit version of the BU0836 to replace the poor quality thrustmaster main board, but is it possible to get any FFB output with the BU0836 chipset?

So in the meantime, to get the new wheel tested and checked, I need a short-term solution. It's the rest of the board I don't care about yet (until I get my Bodnar's), but since the paddle switches connect to the underside of the board (by the D-pad) I don't know how to wire up the paddles without that scrap lol

I had a closer look yesterday at the bus system on the board, and as far as I can make out, almost all of the buttons are wired in serial. The 4 on the upper right are connected to the 2 outer buttons in the lower-middle to create a series of 6, and the paddle buttons are wired into the D-pad for another series of 6. The central button in the lower-middle of the board as the only one that is not connected in serial, it is the FFB on/off switch though.

So, now that I know they are in serial sets of 6, would each resistor be exactly the same? Would I be right in thinking the resistors alter the signal in stages to give a unique signal to the chip for each button pressed?

Jim Cole · Jun 27, 2011

Not sure how it is wired, but resisters show their value with color bands. If they all have the same color bands, then they are all the same value.

Alexander Rhodes · Jun 28, 2011

Ok, I have spent the past 12 hours researching on the web and found what appears to be an amazing tutorial on Circuit building with matrix's, and it seems the buttons on the wheel PCB have been wired the same way, what I thought were resistors, are actually tiny diodes, and therefore it's a simple matrix

Now I just have to work out, what the multiplier is, and make my own matrix. I know there are 6 inputs per matrix, and 10 wires to the board, confusion is that the FFB button is an on/off switch so will be using a resistor, and also 1 LED output to take into consideration, so the output and input of the FFB button would require a minimum of 3 buttons, maximum of 4 am I right?

So how do I work out the multiplier, especially when there are an extra 9 unused connections on the board? Would 3x2 be a safe bet since that would use 6 wires and leave 4 for the FFB button and LED?

EDIT: Link to the easy matrix tut
http://pcbheaven.com/wikipages/How_Key_Matrices_Works/

Alexander Rhodes · Jun 28, 2011

Scratch the previous comments on the board being used as a multiple matrix, all 13 buttons and the LED all connect somewhere on the board, I've been trying to get a circuit diagram together but don't know what a few of the components are around the LED.

It is some wierd setup... I just can't get my head around what they have done at all lol. It's like, the way they have done it, is most of the buttons wire through a diode, through the switch, then on to another diode and so on. But there are some that break the pattern, and go through other components before returning to a diode or exiting the board.

As far as I can tell, the LED runs to 2 semiconductors, but doesn't leave the circuit all the switches are on. It's kind of like a water slide that doesn't get to the bottom, just sort of goes in circles... lol.

Anyone have any clues? I'm about ready to just smash it up and attempt to wire the paddles through the main board without the buttons

Alexander Rhodes · Jul 2, 2011

Ok, something for you

Translations please? I also have the PSD image if you need it, you can find it here:
http://uploading.com/files/7a79m4c7/Circuit+Diagram+RGT+wheel.psd

When I see the circuit, it doesn't look so bad, but it's just hard figuring out how to get the paddles to the mainboard and getting it to think the circuit is fine...

Alexander Rhodes · Jul 2, 2011

Oh yeah, if it helps. There are 10 wires, but only 9 seem to be intergrated into the circuit. The colors are from Pin 1 to 10:
Black
Brown
Red
Orange
Yellow
Green
Blue
Purple
Grey
White (not integrated)

Mean anything?

Alexander Rhodes · Jul 2, 2011

Another update lol. Did a little more research trying to figure what the components where that I didn't know. They are as follows:
??? Transistor Maybe? = Capacitors, color coded by the look of it.
??? Fuse? = Transistors, 2 A printed on them
??? Solder plates maybe? = Resistors, although I don't see a resistor on the board, but they are all labeled with an R+number.

There isn't a middle layer in this board, The 3 pin connection in the top right is also where the wires to the paddle switches connect (sorry if it might have confused anyone).

I'm gonna try and find a datasheet for the main board to see if it helps, I did ask Thrustmaster for one, but they just fobbed me off

Alexander Rhodes · Jul 2, 2011

Found the datasheet, it supports 8x8 multiply. So, 8x8 matrix then? Since it routes to the 4 buttons housed in the stick-shift unit to the 13 in the wheel. Add the 6 potentiometers (maximum 5 inputs recognised by the software) and the 1 LED output. For a maximum matrix, so 24 I/O's in total, that sound about right?

Jim Cole · Jul 2, 2011

For the area that you have listed as ??? Solder plates, is it possible that area was for different versions or perhaps future updates? Maybe a pin header to connect another board or something when the pin header was attached.

Alexander Rhodes · Jul 2, 2011

They are marked as resistors on the board Jim, But definitely no resistor on the top or bottom layer, so most likely as you said for other models. Unless they are using a material to resist flow rather than a component. The only issue with that theory is that the contact plates look to be gold, so I'm still unsure.

All of the tracks do get routed through these though, and they are just 2 square plates sat a track width away from each other, so surely there must have been some purpose for these? Maybe it would have been to incorporate more buttons/feature? Could it be possible they plan to use the same board on the latest model release?