Permanent Traction Override Switch

[mig86]

@joshb86 sounds like something is wrong there. The digital io on the micro is just a transistor. Shouldn't have any issues pulling this line low.

Just sketch up what you have in any format. Bit hard to tell how you have hooked it up from the pics.

Sent from my GT-I9100T using Tapatalk

[joshb86]

Originally Posted by mig86

@joshb86 sounds like something is wrong there. The digital io on the micro is just a transistor. Shouldn't have any issues pulling this line low.

Just sketch up what you have in any format. Bit hard to tell how you have hooked it up from the pics.

Sent from my GT-I9100T using Tapatalk

Hmm interesting. Did this on pin 10 as well. Think something might be up with my board? It was like this from out of the box. I'll get something sketched up soon.

[joshb86]

How's this?

[mig86]

Originally Posted by joshb86

How's this?

A few things jump out.

Firstly, on the switch.
It looks like you have the resistor connected between D9 and the Negative terminal?
And the switch is switching positive?
Normal convention is use the resistor to pull the I/O high (pull up) and then switch to ground to pull the terminal low.
Either way will work, but the convention is safer.
When using a pull up, you need to invert the program logic.

However, when looking at the ATMEGA32U4 documents, I can see that these ports already have built-in pull-ups, you just need to enable for this pin and then you won't need the extra external component.

As for the output, a first thought is to check the voltage between the negative output from your power supply and the vehicle negative (chassis). If this is switching supply they may not be common. The brake ECU signal (VSC) is referencing chassis ground, so the signal needs to be 'low' in relation to this.

But before going any further, one comment you made confused me a bit!

You said "You do need a transistor on the VSC. Without it the digital pin even at low still sets off the VSC mode"

Maybe there is some miss-understanding here? The VSC line you have connected to is low switching, so when you hit the button on the console, it connects this line to ground. So I would expect the IO at low to enable the VSC as described.

The transistor you have hooked up will in effect invert this. So a high IO signal will apply a low to the VSC.

I have an idea what was happening, but before I go any further a question: Before you hooked up the transistor, was the VSC state the same no matter what level the IO pin was?

-Mig

[joshb86]

Originally Posted by mig86

A few things jump out.

Firstly, on the switch.
It looks like you have the resistor connected between D9 and the Negative terminal?
And the switch is switching positive?
Normal convention is use the resistor to pull the I/O high (pull up) and then switch to ground to pull the terminal low.
Either way will work, but the convention is safer.
When using a pull up, you need to invert the program logic.

However, when looking at the ATMEGA32U4 documents, I can see that these ports already have built-in pull-ups, you just need to enable for this pin and then you won't need the extra external component.

As for the output, a first thought is to check the voltage between the negative output from your power supply and the vehicle negative (chassis). If this is switching supply they may not be common. The brake ECU signal (VSC) is referencing chassis ground, so the signal needs to be 'low' in relation to this.

But before going any further, one comment you made confused me a bit!

You said "You do need a transistor on the VSC. Without it the digital pin even at low still sets off the VSC mode"

Maybe there is some miss-understanding here? The VSC line you have connected to is low switching, so when you hit the button on the console, it connects this line to ground. So I would expect the IO at low to enable the VSC as described.

The transistor you have hooked up will in effect invert this. So a high IO signal will apply a low to the VSC.

I have an idea what was happening, but before I go any further a question: Before you hooked up the transistor, was the VSC state the same no matter what level the IO pin was?

-Mig

Hmm I think I even confused myself with the million different variations I attempted. Looking at my photo when I first setup the switch, I had the resistor between the switch and ground(pic attached).

To answer your question... everything you just said makes more sense now. During my testing I don't think I ever tried just starting out with the VSC pin on high. I just assumed that LOW was the way to go so in all my testing the pin started at LOW. I'm surprised I even got it working at all now lol... Helpful to have someone who knows what they are doing look at the setup.

[Dipstik-sportech]

I can't wait until someone produces these!!! Cash in hand!!!

[joshb86]

Originally Posted by Dipstik-sportech

I can't wait until someone produces these!!! Cash in hand!!!

@Dipstik-sportech I will be happy to build you one at cost. Even just today, the joy of starting the car and then realizing the process was now automated made me smile. Let me know if you're interested and I'll gather up the list of parts and the cost. I don't mind doing the labor of building it for free at this time.

[Dipstik-sportech]

Hell yeah I want one!!!

[joshb86]

Originally Posted by Dipstik-sportech

Hell yeah I want one!!!

Great! I'll PM you a few questions. We can customize it as much as you want.

[mig86]

@joshb86 glad to be able to help.

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[joshb86]

Hey Guys,

So 3 of my 7 boards left have been reserved for builds. I have 4 left if anyone else wants a ready to install kit. I'm building & programming these at part cost(free labor) so the only real variable is the type of switch you want and the location you plan on mounting it. PM me if you would like a kit.

[joshb86]

Originally Posted by joshb86

Hey Guys,

So 3 of my 7 boards left have been reserved for builds. I have 4 left if anyone else wants a ready to install kit. I'm building & programming these at part cost(free labor) so the only real variable is the type of switch you want and the location you plan on mounting it. PM me if you would like a kit.

Make that 2 left now... So 2 left that will be made at cost. If you don't get to me in time I can put you on the list for the next batch.

[stugray]

@joshb86,

mig86's suggestions are spot on.
Here is a diagram of how I would do it if starting from scratch.
Clearly yours works, so there is more than one way to do something:



Things to note:
1 - I dont know what transistor you used so it I cant say for sure, but there is a possibility the way you have it hooked up could eventually fry the digital output of the Beetle.
The transistor base input looks just like a diode (to GND) to the beetle, so when it is driving the transistor it is nearly a short to ground to the output (D11).
So I included R2 to limit the current.
A 1kOhm should be fine, but depends on the transistor you picked.

2 - I drew the switch activation as mig86 stated (R1 pulls D9 Hi, and switch pulls to GND)

3- I included a LED output (A0 - config as output) to show status (not required, but some toggle switches have internal LED status indicators)

4 - If you want to hook up to TC switch as well as VSC, then you would duplicate the transistor circuit

5 - On the left of the circuit diagram, I indicate the current (curr with an arrow).
This is the current that when the car's VSC switch is actually depressed flows to ground OUT from the computer (ECU).
If this current is less than 40mA, then you do not need the transistors at all, and these lines could hook directly to the beetle IO pins.
Those pins can sink up to 40mA to ground.
If you tried this and it didnt work, you were probably missing the connection (top of circuit) that connects the beetle 5 volt power ground and the car's 12 volt power ground (chassis).

[joshb86]

Thanks @stugray. After you and @mig86 helped me yesterday I spent the night reading and understanding what you were saying. After more playing around I can see there are multiple ways to make it work, but the more proper ways will be best for the sake of reliability. I left my first prototype as is in my car so I'm curious to see how it lasts. So far it's working, but the most I've let it run powered in the car with frequent use was an hour.

Thanks for a proper schematic as well!