Black & Tan 332iT

[Bry5on]

Alright, this evening I made some more progress. Bench-built the circuit on a breadboard to test it out. After correcting a couple little mistakes, we're in business! The circuit works as designed. Here's the mess of a bench setup I was using to test:


Then I wrapped up the design and decided to have JLCPCB place all the components for me .. and two of them were out of stock. Of course. So back to the design I went, swapping the through-hole op-amp for a surface mount one, and swapping the surface mount capacitor for a through-hole electrolytic. A little rearranging and we were good to go. Order placed.

Updated SMD circuit and layout:



And the board as it will come:


It's a little guy at 28x33mm (those mounting holes in the corners are 3mm), so I'm hoping it'll fit inside the enclosure for the mirror control. If not, George Hill is on the hunt for a spare mirror control module and I may just have to reverse engineer that to include this circuit on a new PCBA that has everything in one

But in the meantime, this should be here next week. There's a couple sets for you and heinzboehmer in there YoitsTmac

And yes, once I'm a bit farther along, I'll post up something in the main forum - as far as I know none of this is documented on the internet anywhere.

[YoitsTmac]

A set for me? I’m so excited. These mirrors have been collecting dust. I’m so excited. As always, this build is awesome

[heinzboehmer]

Awesome! Been a while since I traced through an op amp circuit.

Does the mirror draw any meaningful amount of current from `Dimm Active 12V`? Asking cause the Q3 source is connected after the 100ohm resistor, so the voltage may sag if it does.

Also, not concerned about leaving the Q3 drain floating when dimming is off? Unsure if the mirror has an internal pulldown or similar.

[Bry5on]

Awesome! Been a while since I traced through an op amp circuit.

Does the mirror draw any meaningful amount of current from `Dimm Active 12V`? Asking cause the Q3 source is connected after the 100ohm resistor, so the voltage may sag if it does.

Also, not concerned about leaving the Q3 drain floating when dimming is off? Unsure if the mirror has an internal pulldown or similar.

Nah not really meaningful current wise, maybe 100mA steady state. But that’s a good thought. I’ll check voltage across that resistor during operation.

edit: on second thought I can just move the source over to 12V IGN with a quick trace cut and solder bridge. I think I’ll do that instead, damn.

And regarding leaving Q3 drain open, I’d figured that either it has a pull down or it’ll just consume power until it’s drained. Guess I’ll find out if the mirror stays on for a while

[Bry5on]

Okay, after studying the WDS wiring diagrams and finding there is no clean fused KL15 source, three quick updates:

1) I will cut the trace going to the MOSFET and wire it directly to KL30 at the mirror module, which is fused as Fuse 57
2) I'm planning to snag what looks like the digital 'KL15 equivalent' on pin 5 of X623 going to the mirror itself to power the analog circuit driving the dimmer control and MOSFET on/off. I believe this pin may get power with KL15 k-bus and also under conditions where ignition is off but mirror motors are being commanded (unlocking with key memory, for example). Probing will tell, otherwise I still need to find a KL15 source to prevent parasitic analog drain.
3) Mirror motors are available new as a kit now, so I've ordered those to perform the power folding retrofit while I'm in there. I will not be retrofitting the button, just automatic fold/unfold with lock/ignition. My XTRONS headunit has a fold feature if needed. Bought these: https://www.ebay.com/itm/295814912637

[Ramage]

I'll be curious to hear your feedback on the folding mirror kit. It’s one of those totally unnecessary mods that I’ve always wanted to do!

Looks like I need to order some e90 auto-dimming mirrors

[YoitsTmac]

I really wish I had more time, absorbed by iDrive but I feel like an F30 mirror module is what you want. It can do all motor ops sure but most crucially it does dimming and heating and manages voltages. All you need is power, ground and LIN. It only needs one of two signals: car on/off and lights on/off

[Bry5on]

I'll be curious to hear your feedback on the folding mirror kit. It’s one of those totally unnecessary mods that I’ve always wanted to do!

Looks like I need to order some e90 auto-dimming mirrors

It’s definitely not for the faint of heart as you’ve got to run wires from the central mirror, down the pillars, into the doors, and up into the mirrors. Since I was in there for the roof/windshield/headliner conversion, mirror conversion, and window regulator replacement it made it an easy add-on.

Now mirror folding is much easier! Just door panels and mirror removal.

I really wish I had more time, absorbed by iDrive but I feel like an F30 mirror module is what you want. It can do all motor ops sure but most crucially it does dimming and heating and manages voltages. All you need is power, ground and LIN. It only needs one of two signals: car on/off and lights on/off

It is a totally separate module? I wonder what it’s looking for on the bus as the central rear view mirror isn’t on the bus - it just puts out two analog voltage pairs. Seems to me that integrating the F30 might be unnecessarily complicated? Maybe e90 would be easier, but I don’t think the control modules are packaged in a similar way..

[YoitsTmac]

It’s definitely not for the faint of heart as you’ve got to run wires from the central mirror, down the pillars, into the doors, and up into the mirrors. Since I was in there for the roof/windshield/headliner conversion, mirror conversion, and window regulator replacement it made it an easy add-on.

Now mirror folding is much easier! Just door panels and mirror removal.



It is a totally separate module? I wonder what it’s looking for on the bus as the central rear view mirror isn’t on the bus - it just puts out two analog voltage pairs. Seems to me that integrating the F30 might be unnecessarily complicated? Maybe e90 would be easier, but I don’t think the control modules are packaged in a similar way..

Ah that’s right. I originally explored it as a potential alternative way to control the folding mirrors while also providing dimming, all in the same module. But yes, would need a controller all the same to send these commands. E90 IIRC is controlled by the JBE in the fuse box or else I’d agree.

[heinzboehmer]

Now mirror folding is much easier! Just door panels and mirror removal.

Do you need to run new wiring for the folding motor? If not, you shouldn't even need to remove the door panel. Just disconnect the wires at the mirror adjustment motor/heating element side inside the mirror housing and done.

[Bry5on]

Do you need to run new wiring for the folding motor? If not, you shouldn't even need to remove the door panel. Just disconnect the wires at the mirror adjustment motor/heating element side inside the mirror housing and done.

You run two wires that terminate at the mirror control module. The circuitry to control them (polarity inversion for defined time period) is already on the board but there are no wires for the motor itself. The motor wires do not need to pass through the narrow part of the mirror like the rest of the harness does.

So yeah, door panel comes off but no changes necessary to either the module or coding - other than coding auto-fold/unfold.

[Bry5on]

Alright, I probed around this evening with the door panel off to see what we can do for a KL15 ignition source. Unfortunately there isn't one - The X623 Pin 5 that I was hoping was a digital version of KL15 is 10.6V at idle and 12.5+ vehicle voltage on ignition. The mirror position sensing voltage is the closest thing to ignition but it's 5.1V and I just don't want to pull any current from that line.

So instead of putting the boards in the door module, I'll print an enclosure and put them above the rear view mirror in the headliner. We'll pick up the dimmer signals there, plus the garage door opener ignition and ground source (my opener is the later style rolling code version in the rear view mirror), then pass the dimmer voltage and 12V mirror turn on signal along the existing two wires that are already run to the mirrors. That should work just fine as I ran 20ga wires and the single enclosure for 2 boards is in the printer now.

While I was poking around, I did verify two things.


1) The resistor ladder and method of operation of the mirror switch. The PCBA has 4 220 ohm resistors on it, is supplied a ground, a +5.1V rail, and has an output wire with another resistor on it that floats at 5.1V when open. It also has an open/close switch for selecting driver/passenger side. When you choose a direction on the mirror control, it closes the resistor ladder in 1 of 4 positions, creating a voltage divider that varies from 1/5 * 5.1V to 4/5 * 5.1V (remember, 5/5 * 5.1V is the idle state).


Well, there's one more possible state, which is 0/5*5.1V = 0V. This one is fun. That state is the mirror fold motor control state. So if you are retrofitting folding mirrors and can't get a hold of the correct purple switch, but want to control the mirrors with a button, just short pins 2 (ground) and 4 (switch position) briefly. That's all the extra little button on the mirror control does.

2) I verified the wiring and available pins in the mirror control module. Dropping this table here with my notes in case it's useful to someone else later. My notes still show that I as going to use X18171 pins 3, 6, 9 and 12 but that's no longer the case because of the lack of KL15.

[Bry5on]

Okay, well we left off with the knowledge that we had to move the PCBA to the rear view mirror area. And while I was waiting for the boards to show up, I decided to test the handmade board directly in the car … and promptly roasted the dimming glass on the drivers side. Turns out these things draw up to 200mA of current, which is more than my little opamp circuit could deliver, so it pulled voltage high and killed the electrochromic gel. Good times, and back to the drawing board.

So now that the mirror is toast, no harm in tearing it down to reverse engineer it and properly identify what’s going on inside. So here we go, this is the plastic mirror backing removed with IPA and a plastic blade:



Then separating the layers, this is the heater circuit (Red Pin 3 is positive, Brown Pin 4 is ground). The heater measures 28ohms on my multimeter, and driving the circuit with 13V measured 1.2A for 11 ohms at steady state. Note that the ground has a separate trace that follows the perimeter of the glass and terminates at that wire at the bottom. This is actually the mirror gel ground, it just lives on the heater layer.


Here we have the second layer, this one is for the dimming gel and this is where it gets interesting. Pin 1 has a trace that follows the perimeter of the mirror and terminates at the positive gel wire. Pin 2 has a squiggly resistor just like the heater that also measures 28 ohms, but it terminates to Pin 1.



What does this tell us? Well Pin 1 will drive the mirror dimmer directly and Pin 2 will drive it through a current limiting resistor. My working theory is that the factory module drives through Pin 2 and closes the loop by measuring voltage at Pin 1. Well I’m just going to drive Pin 1 directly because I think that’s easier. So we can ignore Pin 2 entirely. Only one wire needs run per side to retrofit dimming in the end.

And now back to the circuitry. The boards arrived and look sweet! But unfortunately they’re not usable given the opamp learnings above.


So I got to work on hand-fabbing a board that does the same function and passes current through a transistor instead of through the opamp. I also neatly designed an enclosure that clips into the sunroof mic cover, which also includes a dual USB-A output for the dash cam. Much tidier than what I had before and uses factory pins and factory-like connectors. Here’s that:




I actually don’t have a photo of it final installed as it looks like there’s nothing there B) And voila! We now have auto-dimming side mirrors and functional mirror heating again.

in the next chapter we’ll get to work on mirror tilt.

[heinzboehmer]

Man, that's super tidy. Good stuff!

[Bry5on]

Alright, guess we're not done with the mirror dimming just yet. Here's the schematic for the dimmer that works (both sides)


And why not design a little tiny PCBA that does both sides, just because we can


And an enclosure for it


Ordered a handful of these PCBAs, so at least they can be recreated for retrofits in the future