champaned_out

iTrader: (2)

Hey guys I recently purchased a 05 to w/navi and I have a 32gb nexus 7 collecting dust in my room. I read most of the threads with the nexus install but when it comes to wiring I have no idea where to start... does anyone have a simple wiring diagram specific to the tl? Also other diy tutorials seem to have a 2channel amp... would I need a amp also?

triax37

iTrader: (1)

Good wiring information can be found here (13th picture down):
http://forum.xda-developers.com/show....php?t=2113259

And here:
https://acurazine.com/forums/3g-tl-audio-bluetooth-electronics-navigation-94/my-nexus-7-usb-rom-install-902876/

In general, you need to wire the Nexus to an OTG cable that has a y-connector - one side will charge the Nexus, one side will connect to a USB hub that can power multiple other devices (external USB storage, a rear view backup camera, etc.). Make sure the power adapter you use can push through 2.1 amps - the standard adapter I believe is 1.0 amps and may trick the Nexus into recharging at 500 milli-amps (standard rate over a USB connection), which will not recharge the battery enough while you're using it.

I don't think you need an amp for the TL, but if you're already taking apart a portion of the interior, some believe it's a good time to route the Nexus 7 signal through a DAC to a 4 channel amp to power the speakers. I'm probably not going to go down that route immediately, as I just want the tablet in the car, streaming Pandora, accessing google maps and my calendar, with a functional rear backup camera, but it's another option.

Good luck! I have most of the parts, and plan to start the install in two weeks. Can't wait!!!

EvilVirus

iTrader: (8)

OP there are tons of threads that show how to install a tablet into our cars. You are going to have to search and read. Start off by what triax gave you.

RxWorld

The thing that stops me from pulling the trigger on this project is losing the backup cam. Is there anyway to integrate the stock backup camera into the nexus? From what I can see, I think it would be tricky...

triax37

iTrader: (1)

The quick answer is "maybe." I've been evaluating a few different options for the back-up camera and am waiting on a Febon 100 USB adapter from China (2 week order, $77 shipped) that included the UVC drivers and I believe will allow me to connect a standard aftermarket back-up camera ($15) to the Nexus via a USB cable. I tried a few other options (below), but I believe the Febon will be the solution.

- EasyCap - this is a USB video capture device that I tried to connect to the OEM back-up camera, but I believe it doesn't work because neither the camera, USB capture device or the Nexus includes standard USB Video drivers (aka UVC).
- WebCam (logitech c270) - this works with the CyanogenMod linked below, because I think the camera includes the drivers needed. But I'm concerned the webcam would freak out when Colorado temps drop below 30 degrees. The recommended operating temp is 32F-100F.
http://mehrvarz.github.io/nexus-7-usbrom/

I know there is some additional cost here, but you can easily sell your OEM back-up camera for $100+. From my perspective, this is the main sticking point on this whole tablet replacement of the navigation modification, but I feel like I'm close to solving it. I'll post my updates to one of the main tablet mod threads...

RxWorld

Speaking of below zero temps. I was reading one install (not on azine) of someone having problems booting up their tablet in the cold. I wonder if there is a work around for that?

triax37

iTrader: (1)

No solid suggestion on that one, but I believe it's just the screen that has issues until it warms up. Maybe a small neoprene cover for the screen?

There is some commentary about heat being an issue as well, as the battery won't recharge (and the tablet may not startup?) if the temps are 120+ F, possible in the west and south. Some have suggested replacing the original battery with a sealed-lead acid battery and hooking that up to the car battery (behind the firewall). I found a battery for $20, and may tackle this if it's a problem for me this summer.

Discussion: http://www.reddit.com/r/Android/comm...al_because_of/

Battery (I think this would work): http://www.batteryspace.com/sealedle...ery4v9ahs.aspx

triax37

iTrader: (1)

Update: received the Febon 100 yesterday, tested it and it worked! No additional coding or commands needed - just plugged the Febon 100 into the USB port, and the existing backup camera (RCA plug) into the Febon, and started the DashCam app and everything looked good. I'll do some more testing next week (I'm traveling this weekend) and confirm it's fine after repeated starts/restarts of the car and sleep/wake cycles of the Nexus 7.

RxWorld

That's awesome triax, thanks for taking the lead on testing this for us!

mzilvar

iTrader: (3)

Careful with replacing the battery.

Connecting it to the OEM battery is a bad idea.

If you connect one terminal of your battery to the car battery positive and the other to ground (chassis) you've effectively connected two lead-acid batteries in parallel.

This is going to cause currents to take place between the two batteries using the following formula:

I = (V1 - V2) / (R1 + R2)

If you were to connect it in series, then your car's voltage would go from 12V to 16V and that wouldn't be good for anything in the car and would also be a bad idea.

The safe way to connect another battery to the car's electrical system is through a DC - DC power supply. The same way as the Nexus 7 or your cell phone is charged when you plug them into an accessory slot.

You have a DC - DC power supply that drops the car's voltage from it's operating voltage (normally 13.5V, but may vary depending on your car) to a voltage suitable to charge your cell, in the N7 it operates off of 5V. It's safe to do it this way since your DC to DC power supply isolates the battery from the car's battery and charging system allowing you to connect another battery without throwing the rest of the electronics in the car off.

Also the charge and discharge rates of lead-acid batteries are different from a Lithium-Polymer battery that is in the Nexus 7.

As an example I use Lithium-Cobalt batteries (the most hazardous of the Lithium chemistry cells but also most energy dense) in some lights that I have for diving that I've modded. The Lithium-Cobalt chemistry has a maximum discharge rate of 2C or 2 X (capacity of cell), since I use 3.1Ah cells my max discharge current for safety is 6.2A, I operate them at 2.8A with a CREE XML LED.

Next is the charge, for my Lithium-cobalt batteries the max safe charge current is 1C, however charging them at less than 1C extends the battery life. Mine are charged at 500mA or about 0.16C.

For the battery you've chosen the max recommended charge current is 3A, which should corresponds to about .3C. Since it has 2 cells the data sheet shows your power supply is going to have to operate at 4.8V to 5V. Which is going to take 16 hours to fully charge it from 100% discharge or 10 hours from a 50% discharge.

This is where a big problem comes in. The Nexus 7 is regulating the voltage on the battery. So it's controlling how fast or how slow the battery charges. The Li-Poly battery can be charged at a much faster rate than the lead-acid battery. Now charge the lead-acid battery at the same rate as the Li-Poly (since the N7 is regulating the charge rate) and you're going to damage that cell.

Also the nexus 7 battery has like 5 wires on it, I don't know what it uses all 5 of those wires for. The lead-acid battery has 2 terminals, positive and negative.

The data sheet also shows it will only last about 10 minutes being discharged at a rate of 30A or about 3 hours at 2.5A. I'm not sure just how much current the N7 draws from it's battery while it's operating, but it's going to vary depending on things like the screen brightness, which radios are turned on, processor state, etc. etc.

The Li-Poly battery is a lot better suited to the Nexus 7. It provides a high rate of discharge since the N7 is a power hungry device, can be rapidly recharged and is more energy dense than a lead-acid battery (smaller for the same capacity as lead-acid).

There's a lot more involved than just connecting a battery that has such and such cell voltage and such and such capacity in amp-hours.

I think a more effective way if there's a heating or cooling problem in our car is to do it the way swoosh did his.

He opened the AC vent behind the Nexus 7, so his AC cools the tablet in the summer when it's hot and heats it in the cold of the winter.

With that said I went a different route, I installed a fan to plexiglass on my install. I've had no problems, but I live in Hawaii where temps are about 80F year-round.


Good job with the camera though, I've come up with a trick that may work for the JEXR so you don't have to disassemble anything near the steering wheel if you want to get control of those buttons.

Trick is there is an orange wire at the headunit that comes from the HFL buttons, if this one is snipped and the harness side is used as the positive wire for the JEXR connection.

Then the other wire is up by the hands-free link, simply snipping this one and connecting its harness side to ground up there would do the trick.

Then connect a third wire to a ground by the headunit and connect this to the negative wire for the JEXR connection (one of the resistive USB inputs on the JEXR). Can check the resistance between the wire that was attached to chassis off the HFL harness and the wire that was added by the headunit, it should be about 0 ohms. Effectively what I'm planning on doing eventually is doing this to use the car's chassis to complete the connection.

That'll pass the resistive HFL buttons off the steering wheel into the JEXR without messing with the reel in the steering column or dropping the headliner to run a wire from the top down.

You can get the reverse light sense off your car using the JEXR as well, that way it'll automatically open up the camera on the tablet when you put your car in reverse.

I haven't played with a JEXR yet, but it's on my list of things to do eventually.

triax37

iTrader: (1)

Wow...I think your brain just overcharged my brain! I'm going to need a day to fully appreciate the knowledge you just shared, but in the interim, I think the solution is to open up that A/C vent and possibly include a small USB powered fan back there that I can use as needed on hot days. Thank you, sir!

mzilvar

iTrader: (3)

So I actually had some of the wires wrong just to correct myself in case someone else tries the JEXR thing.

The audio unit has a brown wire attached to it that is already tied to ground and is a ground for the steering wheel switches as well.

So I'd have to figure something else out, like splicing the orange wire by the HFL in the roof to one of the un-used audio wires from the HFL that goes to the headunit and then taking that wire and going into the JEXR on the + and then just tying a ground to the - for the USB input and maybe that would work.

I haven't played with it yet, just wanted to mention that in case someone else tried what I posted.

tjl_48

So the existing backup camera has just an Rca plug? Also any idea if this flebon would work with the 2013 nexus 7. Just finished my install this weekend but if it would work I'd add it.

mzilvar

iTrader: (3)

Seems like triax is using a USB-capable ROM so I'd doubt it'll work on the 2013 N7 unless you have some sort of USB-capable ROM loaded onto it.

triax37

iTrader: (1)

I'm using the 2012 Nexus 7 and an aftermarket reverse camera. Apologies for any confusion!

tjl_48

I have timurs USB kernel for the 2013 N7. Tried lading the drivers for an easy cap to use an aftermarket camera as well but couldn't get it to work. There doesn't seem to be much support for the newer n7 yet.

triax37

iTrader: (1)

I checked with the Febon seller and he said the device could would work on a Nexus 2013, if running Android 4.3 and was not rooted. I'll test the product some more tomorrow and will report back.

dwb993

iTrader: (13)

Update? Subscribed

triax37

iTrader: (1)

My install experience is here: https://acurazine.com/forums/3g-tl-audio-bluetooth-electronics-navigation-94/nexus-7-2012-dash-install-my-experience-links-parts-list-pictures-911259/#post15014367.

Thanks to everyone, mostly Turbocoop, 00g, NitroViper, and mzilvar! Wasn't sure whether to post my thoughts in this thread or make a new one, but given the post length, I made a new thread. Please direct questions for me in that thread.