Lexus RX Steering Wheel Buttons

PaulRB:
Oh, you mean the link in post #16? Seems to be for the entire vehicle. Did you find schematics for the 2 pcb you want to use? Please post those. If they are detaile enough, you may not need to make your own.

Yes, I found multiple schematics for the 2 Steering Pad Switch pcbs, but I don’t know if they are enough. I searched for “Steering Pad” in the linked document and I attached them as a PDF below.

Steering Pad.pdf (148 KB)

Hutkikz:
And this is the best description I’ve seen.
While it’s far from the best program for the task, the real problem is noob’s posting the breadboard view instead of the schematic view and that’s simply because that’s what they understand better.

+1 karma. Thanks for having an open and critical mind.

androidftw:
Yes, I found multiple schematics for the 2 Steering Pad Switch pcbs, but I don't know if they are enough. I searched for "Steering Pad" in the linked document and I attached them as a PDF below.

They are lacking in detail, but useful. You need to figure out which pins on the pcb connectors correspond to the connectors shown in those diagrams.

PaulRB:
They are lacking in detail, but useful. You need to figure out which pins on the pcb connectors correspond to the connectors shown in those diagrams.

Thanks for the reply. I found more schematics and guides. I also found a Steering Pad Switch pinout with resistance measures from two other Lexus models.

SM_3-1 export.pdf (384 KB)

SM_1-1 export.pdf (148 KB)

Let’s say that I came to a conclusion that these are the pins on the main connector z5:

1 HORN
2 DISP
3 GND1
4 DIST
5 LED
6 ECC
7 +DP
8 EAU, SWG
9 AU2, SW2
10 AU1, SW1

I am assuming GND1 stands for Ground 1. I am also assuming that SWG stands for Switch Ground. Let’s say that I want to test if LED is indeed Pin 5 by lighting up the Switch LEDs with a 9V battery. Would I need to attach a resistor, or are the built in resistors on the PCB sufficient?

I am also coming to a conclusion that the way the button inputs are detected by the vehicle depends on the resulting resistor values of the buttons. For example, if VOL+ is pressed the resistor reading is 950 Ohms. If VOL- is pressed, the resistor reading is 2.9K Ohms. I noticed that buttons with similar resistor readings are divided between pcb SW1 and pcb SW2.

If the above is true, can I just connect SW1, SW2, and SWG to an Arduino with a known resistor value to make an Ohm reader? Then, depending on the Ohm reading, the mapped keyboard ouput results? Similar to How to make an Arduino Ohm Meter - Arduino Project Hub

I think you are correct. However, you can simplify things compared to that ohm meter project. You don't actually care about measuring actual voltages or resistances, you just need to figure out what range of 0..1023 readings from analogRead() you get from pressing each button (or no button).

What resistor value(s) are in series with the leds? Are those the 680R you asked about? That would seem a sensible value for white leds and a 12V supply. Try them with 5V. If that's bright enough then great. Otherwise you will need to figure out a way to supply a higher voltage, such as using a voltage doubler circuit or a 5V to 12V booster module like this:
s-l300.jpg

s-l300.jpg

PaulRB:
What resistor value(s) are in series with the leds? Are those the 680R you asked about? That would seem a sensible value for white leds and a 12V supply. Try them with 5V. If that's bright enough then great.

My question was in regards to the built-in resistors on the PCBs. Considering that there are built-in resistors on the PCBs, can I directly attach a wire from the PCB connector to the Arduino? Or would I need to attach a capacitor or resistor to prevent the Arduino's 5V from burning the PCB?

androidftw:
My question was in regards to the built-in resistors on the PCBs. Considering that there are built-in resistors on the PCBs, can I directly attach a wire from the PCB connector to the Arduino? Or would I need to attach a capacitor or resistor to prevent the Arduino's 5V from burning the PCB?

I understood your question. The answer depends on the value of the series resistors. That's why I asked about them. I cant read the values from your pictures, too blurey.

PaulRB:
I understood your question. The answer depends on the value of the series resistors. That's why I asked about them. I cant read the values from your pictures, too blurey.

Sorry for the misunderstanding. I uploaded less blurry pictures on imgbb at Steering Pad Switch PCB — ImgBB

Please post them here on the forum.

PaulRB:
Please post them here on the forum.

Here are the pictures. They may not be as clear as on imgbb, but let me know and I will try to upload larger sizes in multiple posts if needed.

IMG-20200830-154615.jpg

IMG-20200830-155241.jpg

IMG-20200830-155442.jpg

IMG-20200830-155520.jpg

IMG-20200830-155529.jpg

IMG-20200830-155606.jpg

IMG-20200830-155736.jpg

IMG-20200830-155741.jpg

IMG-20200830-155927.jpg

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IMG-20200830-160010.jpg

Well, it's odd. I was thinking that the smaller size resistors are the series resistors for the leds. They seem to be located close to the leds. But why are they not all the same value, for even illumination? "6800" is 680R which is perfect for a white led with a 12V supply, as I said before. That would result in a current of 13mA. But others are "2201" which is 2K2 which would be only 4mA. "1003" is 100K which would give a tiny current, less than 0.1mA. Also there are "3300" which is 330R and that would give a current of 27mA, which sounds a little high for such tiny leds.

I think it should be OK to connect 5V, but not 12V until you have figured out exactly which resistors are connected in series with the leds.

PaulRB:
Well, it's odd. I was thinking that the smaller size resistors are the series resistors for the leds. They seem to be located close to the leds.

Thanks for the input. To be honest, I am not too concerned about the LEDs even being on. As long as the buttons work, I wouldn't risk the LEDs blowing and ruining the circuit.

The main concern is if the buttons themselves need resistors, diodes, capacitors, or anything else attached.

I am only planning to attach the SW1, SW2, and SWG pins to the Arduino.

Well, as I said, you should be safe with 5V. Even those lowest 330R would only allow 4~5mA which would be fine. In these situations, the is more danger of damaging the Arduino than damaging the pcb.

For the switches, as you already figured out, you just need a known resistor for each arduino analog pin (between 5V and the pin). Try 10K, 4K7, 2K2, 1K... and see what analogRead() gives for each switch.

PaulRB:
For the switches, as you already figured out, you just need a known resistor for each arduino analog pin (between 5V and the pin). Try 10K, 4K7, 2K2, 1K… and see what analogRead() gives for each switch.

I attached a breadboard view of how I am planning to connect the SW1 and SWG pins along with the known 10K resistor. Did I connect everything correctly? For some reason, something seems off with my breadboard sketch… As if there is an incomplete circuit…

If I am not mistaken, SW1 is for the first Steering Pad Switch. And SWG is Ground for both of the Steering Pad Switches.


Looks OK to me.

I notice you are using an Uno. Remember what I said in post #2. You can use Uno for testing, but not suitable for your finished project.

It would be helpful if you could start showing your images in your posts. Attach the image to your post and post it. Then right-click on the link to the attachment and copy the address. Modify the post, click the insert image icon and paste the address.

PaulRB:
Looks OK to me.

I was wondering how to post the pictures directly in the post. Thanks for letting me know.

Regarding the UNO vs Pro Micro, I know the differences between them. I also know that Pro Micro is a lot smaller than the UNO. I do see a few advantages, but just to clarify, why is the Pro Micro more suitable in your opinion?

You want to build a circuit that will act like a pc keyboard, mouse or multmedia controller when connected via USB. Uno can't do that. Pro Micro, Leonardo, and many other atmega32u4 and samd21 based arduino can, because unlike Uno they have a "native-usb interface".

PaulRB:
You want to build a circuit that will act like a pc keyboard, mouse or multmedia controller when connected via USB. Uno can’t do that.

Thanks for the clarification. So I am assuming UnoJoy for UNO is not the answer?