My Solution To Steering Wheel Controls

jcdillin · 08-23-2005, 08:12 PM

Well everyone I had another hair brained idea

I wanted to have steering wheel controls in my car but
1. I didnt want to modify the cars stock wiring
2. I was not able to safely route a wire up through my steering column to get to the control buttons.

Since I had 12v present inside the steering wheel I decided to go with a microcontroller and some $17 wireless modules from sparkfun. So not only can I wirelessly send button presses to the computer in the trunk I have endless possiblities for button combinations in the future. I could even add datalogging of sorts. So 2 microcontrollers and about 10 PCB's later I ended up with this.

The PCB on the top is a receiver board I created and the board on the bottom is of course the transmitter board. I used a PIC 16F628 for the transmitter board, because well I had one already and I wanted expansion for later on so with 1k of code space and i'm only using 1/3 of it I should be fine. The receiver is using a PIC16F458 which yes is way overkill for what it is doing right now. I will be downgrading it to a F628 when I get it.

The receiver board has a standard PC DB9 connector which i'll use to connect to my computer.

Here is a closeup of the transmitter board

Here is a picture of the steering wheel buttons I ordered from volvo.

This is the transmitter board with the PIC in it's socket and the TX module mounted.

just have to finish wiring everything up

there is a picture of the stock volvo pcb and the bottom of my board

And finally there is everything next to a quarter for a size comparison.

So thats pretty much all the hardware and it's pretty simple in operation, it just takes button presses and converts them to a standard serial output which I will program girder to respond to.

I will post pictures after I get everything installed in the car, even though you really will not be able to see anything after it's done

jcdillin · 08-24-2005, 06:48 AM

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Scouse Monkey · 08-24-2005, 03:12 PM

i hate to say it Jerry but you done it again you flash git!

jcdillin · 08-24-2005, 06:57 PM

thanks

Mad Ad · 08-25-2005, 10:56 AM

Jerry - slightly off topic but you seem to have your head in gear on these.

My radio control paddle is a 5 switch paddle. I was intending to hack it to a gamepad and use steveg's software but ive investigated the stock wiring and ive come up against a problem. My paddle is mounted on the wheel so I cannot run/hack extra wires in, it would twist around the wheel so I have to use the stock connection method (which is routed through the rotary coupler).

Instead of the paddle having a discrete wire for each press, its a 2 wire resistance bus for the whole paddle. This presents a different value at the 2 wires, from 0 Ohms to 1.6K depending on which switch is pressed. These resistances are obviously decoded at the radio since my factory manuals shows the wire pair just routes straight to it.

As you can imagine, this presents a problem interfacing to the switches on a USB gamepad. The only solution ive got so far is feeding a voltage into it and use a LM3914 to make a comparator circuit that I can maybe drive a relay bank with, triggered by whichever button is pressed but thats a bit of a long winded approach (albeit quite cheap).

I mean to get from the paddle to the computer im having to abuse the led display circuit to interface paddle to the pad circuit to plug into the pc and I was wondering if you had any ideas of a simpler way to read the resistances from the bus and convert them into on/offs that can be stuffed up the USB socket.

Bear in mind that im looking for a cheap solution and so far the pad would cost me a fiver and the IC and parts for the comparator would be perhaps another ten (plus a day trying to figure it all out, lol). Ive a feeling its probably the only way i can do it but I dont know unless I ask.... what do you think there Jerry? Im not interested in radio control or anything fancy as its all up front (pc, steering etc) just a simple wired link would do me- Id just like something simpler than adapting a comparator.

Thanks for reading.

Tony G · 08-25-2005, 11:47 AM

There's a genius in Florida! Girder: under-used.. (I guess you're using Marks serial plugin)

Those PCBs look production ready. What are your plans (if any)?

I already use 16F628 in-car for Head unit command and audio, and start-up controller, so just post the binary and schematic!

Are you having to change steering wheel btw?

thanatos106 · 08-25-2005, 11:53 AM

Quote:

so just post the binary and schematic

After the XM thing, I don't think so.

Nice job JC.. cool stuff. Boris

jcdillin · 08-25-2005, 12:13 PM

Quote: Originally Posted by Tony G

There's a genius in Florida! Girder: under-used.. (I guess you're using Marks serial plugin)

Those PCBs look production ready. What are your plans (if any)?

I already use 16F628 in-car for Head unit command and audio, and start-up controller, so just post the binary and schematic!

Are you having to change steering wheel btw?

Honestly I didnt have any real plans for it, I just wanted to have some steering wheel controls. I will be happy to share the information on it though with anyone if they would like it. The PCB's are very generic and would work with pretty much any type of steering wheel buttons.

I am going to put the code and schematics up on my website in a few days, I just need to clean all of the test routines and stuff out of the code

nope, thats the beauty of it, my current steering wheel is capable of holding these buttons, I just have to remote the cap that is there now and pop in my modified buttons.

jcdillin · 08-25-2005, 12:16 PM

Quote: Originally Posted by thanatos106

After the XM thing, I don't think so.

Nice job JC.. cool stuff. Boris

I know, but we must let bygones be bygones

thanks

Scouse Monkey · 08-25-2005, 12:40 PM

Mad Ad, you could possibly hook your analogue connections up to a joystick port and then use a joystick/HID plugin for girder?

I used to have my RC car reciver hooked up to a couple of servos turning Pots connected to my joystick port for very low tech way to play racing controls from ym bed using my RC car controller (i had a fully bling RC car setup so throttle curves came in handy in GP2)

Bravellir · 08-25-2005, 01:10 PM

@Mad Ad: AFAIK the sony remote x2s works in a similar way, and we successfully interface it to a joystick port using a plugin for girder made by Curiosity

Scouse Monkey · 08-25-2005, 01:51 PM

yeah i was gonna say use the sony joystick solution but I forgot as I was cooking dinner

Mad Ad · 08-26-2005, 07:45 AM

Joystick port? You mean the one that comes with a sound card? bugger, ive not got one... perhaps a usb joystick?

Can someone suggest what joystick would be suitable please?

I take it from this that joystick pads work on a resistance basis, so what, id just have to map the different resistances to outputs? I'll take a look at girder and see if I can figure it out. Thanks for the suggestions guys

Curiosity · 08-26-2005, 08:58 AM

I actually developed that plugin using my analog steering wheel controls since I don't have a Sony stick. Any USB gampad will work as long as it has an analog stick, or a USB joystick adapter, but the one from Radio Shack is difficult to work with. They all are designed for ~100K ohm pots so 1.6K at most makes it hard to get a good reading. You have to sort of fake a pot with a couple resistors to make it think that resistance is center and the buttons pull it some % one way with a large enough difference between each button/resistance. Here's a couple threads on it. god_of_cpu made a really nice standalone app too.
http://www.mp3car.com/vbulletin/showthread.php?t=25690
http://www.mp3car.com/vbulletin/showthread.php?t=21978

Mad Ad · 08-30-2005, 10:32 AM

Excellent explanation Greg, thanks a lot- although it took the weekend to read through the threads and get my head around it

I ruled out Girder as soon as I realised it cost way more than the parts to make a comparator however if god_of_cpu's application still works, then all I have to do is get a gamepad with an analogue stick and try it out- I have to get a pad anyway so ive not lost much if it doesnt work. Since my controls are a simple 2 wire with no power it should hook straight in place of the pot (with an appropriate resistor).

I'm off to get a gamepad

Thanks again Curiosity