So I FINALLY did the sat nav mod...

Matt_C

04-02-2022, 09:18 AM #1

This was the original thread when I first thought about doing it http://www.outlawjapclub.co.uk/forum/sho...hp?t=11814

And now it's finally done! Ok, so I haven't actually been doing it for years, I popped it back in it's box and more or less forgot about it until recently when I joined the IS Facebook page, and those gits got me back into wanting to mod again - I swore I'd leave this car alone!!!

So, here's a shorter write up of the one I did on LOC (which was an ongoing one as I did bits here and there)

Started out with the later 7" variant (which I got for a bargain) and a cheap Chinese GPS that turned out to be free, since they sent me the wrong one, as it didn't have the AV input for a reverse cam. So the plan was to get it all in and working, and it didn't matter if the GPS tablet was killed in the process since it owes me nothing.

As far as configuration goes, what I wanted was for the housing to act as it should - both the open/close button and the tilt button to work, as well as the automatic close and reopen with ignition. And for the GPS tablet, I wanted to rework it so that it turned on when it got a USB power feed on ignition, and turn off again when that power feed was removed, on ignition off. Basically the same way the Sony and Garmin sat navs work.

Thinking about the wiring, plan was to tap into the stereo wiring plug for the five wires to the housing; perm live, switched/acc live, ground, illumination + and illumination - (illumination + and - are so the buttons light up), and for power to the GPS tablet, tap a female 12v socket onto the wiring for the original cig plug under the console, and simply plug in the supplied 12v to USB adapter that came with the nav. So, 5 wires for the housing, and 2 for the GPS power.

First things first, I ripped the housing apart to remove the screen;

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And gave the GPS tablet a quick test fit (sorry for the dark pics)

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Absolute perfect fit. I knew it would as it is pretty much the same as the one mattlaw did, which was the inspiration for this whole thing anyway, but I was still amazed at just how well it fitted. Inside the housing you have about 182mm width and 112mm height - this thing is 180x110, so pretty much perfect. The other amazingly lucky thing is the screen (of the GPS) isn't actually dead centre - the black band around it is thinner at the bottom than the other three sides, so the viewable screen area is slightly offset, and it's this that turned out to be it's saving grace - if it had been dead centre, I wouldn't have been able to get the tablet to sit low enough in the housing to see the whole screen and would have meant cutting, which I really didn't want to do (I wanted it all to look as OEM as possible). So pleased with that. It also sits almost perfectly flush as there's no protruding bezel on it, so looks nicely OEM when it's in.

So then set about ripping the tablet apart - the connectivity is all on the side of the unit, and there isn't room inside the housing to plug anything in. I'd have to rip it apart to get to the PCB anyway, and I wanted to relocate it if possible, thus avoiding having to solder directly onto it for power etc

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With the PCB loose, I can easily plug a USB cable in for power without having to solder directly onto the PCB, thus making the USB port still operational if I need to plug it into a computer for updates etc.

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I drilled a couple holes in the back casing to cable tie the PCB down, and glued a couple of crude wooden blocks to the sides of the housing. Reason for this is it holds the tablet perfectly snug and tight, but allows me to slide the tablet out if need be - more on that later;

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The reason for being able to slide it out is 1) in case I need to plug it into my computer for anything, and also 2) this is just the test bed. Because this GPS owes me nothing, I'm happy to experiment with it (I've also compromised the screen ribbon cable, so it's a bit iffy displaying an image), but if we can get this all working how I'd like (which is to try to replace the GPS on/off switch with a trigger, so that it powers on with ignition and off again with power cut) then I'll buy a newer one, this time with the AV input for reverse camera, and possibly also with bluetooth so I can (hopefully) connect my phone to it for handsfree (the idea is I can plug the 3.5mm jack from my Grom into the tablet, and possibly solder a separate mic onto it, rather than use the internal mic, which of course will be inside the housing.

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Matt_C

04-02-2022, 09:54 AM #2

This is where it sat for another month or so because the next part was the biggest problem - I know sod all about electronics, and I can't solder for ****. Like, I'm really bad at it. Fortunately, a work colleague friend of mine is a dab hand with electronics and soldering, so agreed to help me with that side of it, so I carried on buying in little bits here and there to have ready when we had a day off together to do it all

For the wiring to the pins on the back of the housing, the original plan was to use the smallest female crimps I could get (2.8mm I think?), which with a little bit of crushing in a pair of grips fitted snugly on the pins. But I wasn't happy with how close together they were, and they'd need to be insulated with heat shrink so they didn't short out. The plan at this point was to run those five wires into Molex connector, and run the 5 wires off the stereo plug into the other part of the connector, so that it was unpluggable

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Luckily, a guy breaking a 200 on the FB page supplied me with the wiring plug (with about 4" of wiring on it) for a tenner, but annoyingly, this was missing two of the pins I needed! The ones missing were pins 13 and 25 in the diagram above. So I hacked up an ISO harness I'd had for years but never used (think I bought this to use on one of my Escort RS Turbo's about a decade, or longer, ago) and with a bit of manipulation with pliers, I managed to get a couple of the pins in the Lexus plug and make a good enough connection for it to work!

Here you can see the two wires (orange and yellow) I took from the ISO plug fitted into the nav plug. Trimmed back all the others I don't need, and left the three on the other end that I need.

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And a little video of it being tested;

https://www.youtube.com/watch?v=kPiDR6u7dUE

Then, while playing with my Grom in the IS, Bluetooth was struck off the list. Although my Grom unit has USB, iPod and AUX (3.5mm jack) connections, and you can switch between them using a key sequence on the head unit, you can't actually have them plugged in at the same time. Tested this by having my iPod playing (iPod connection) and iPhone also plugged in (AUX) with a vocal speech playing (to replicate voice directions for a nav, or the callers voice if I was taking a call). Whilst both will function at the same time - iPod music is playing and I can hear the speech over the AUX, the volume is halved for both devices. Unplug the AUX jack and the iPod is restored to full volume. Considering that I'll be using the iPod 99% of the time, and the AUX would only really be used for taking a phone call (I almost never use voice directions on sat navs) this is no good to me. Shame they aren't isolated and would only work by switching inputs on the Grom, but I guess it's not to be. I'd never use the GPS media functions for music, as I have iPod for that - with much better control and sound - there's no reason to use video playback either; 1) because I can't see the point in converting video files to the correct codecs and resolution, putting them on a card and playing them back while driving anyway, and 2) because there's no point having video with no audio. So there's probably no real reason to get the card reader extender cable thing I linked to either, as the microSD card slot would solely be used for maps now, so I shouldn't need to get to it, to hot-swap.

So we're back to only two core functions; touchscreen turn by turn offline maps (ideally TomTom if I can hack it to run) and reverse camera (which means replacing the GPS tablet with one that has an AV input - version 2.0!)

Next, ordered up some of these JST connectors

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These are so I can cut the USB cable in half, feed it inside the hole in the side of the housing, and connect one of these to the end of the USB cable (outside the housing) and the other to the other end of the USB power cable, so it's easy to unplug if I need to remove the housing from the car. Even though I'm using the supplied 12v adapter in a cig plug, I wanted that mounted down and out the way, so it wouldn't be accessible without removing the heading, so this seemed like a good idea.

Next, ordered up the wiring for the stereo to nav plug, along with a nice flexible pvc sleeve to try and make it look as OEM as possible (I like things neat). Tried to match the colours as closely as poss to the nav plug end, so we've got orange, yellow, green, grey and white. Some of these matched up to the radio end, but not all of them! Never mind....

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So then we fast forward to Monday just gone, when both my work mate and I had a day off together, so after I helped him in the morning cut and fit an internal bulkhead in his van, we then spent the afternoon soldering this all in.

First up, make up the "loom" for the nav housing;

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Stripped out the dash;

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And started on the bit I was dreading the most - cutting into my nice, virgin, unmolested Lexus loom!!! But we did it properly with it all soldered nicely and correct sized heat shrink used on each wire, cutting the original loom sleeve open to expose the wiring, and then taping it back in place afterwards, so again it looks nicely OEM. Didn't really get enough pics of this as we went on, sorry, but light was fading so we just cracked on

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With that done, the "loom" routed up the dash and out the top, and the housing tested and working, we went back inside to fiddle with the GPS tablet. First off, a couple repairs - the white charging wire from the battery had broken off when I was manhandling it, along with both the wires that connected the on/off button. So the charging wire was soldered back on, and we soldered on two long thin wires for the on/off, and tested them with a meter thingy. Turns out it's just a simple circuit breaker - one wire is showing a constant 3.7v, and the other nothing. So when the button is pressed, and held, it completes the circuit and the tablet powers on. Press and hold again and it powers off. So with that in mind, we looked at trying to find a way to give it a 3.7v feed on ignition (or ACC on) for a couple of seconds, and again for a couple seconds when ACC was cut off with ignition turned off. Couldn't see an easy way to do this (googling suggest a power pulse generator circuit needs making, but this didn't seem easy and neither of us knew how to go about it. So we then looked at using power from the housing motor to feed it the required voltage, seeing as that runs for a couple seconds on open and close, but encountered two problems;

1) the motor actually kicks out 9-10v, and
2) the red and black wires on the motor aren't positive and negative - they're forward and reverse! So we'd have needed to connect both wires to just one of the wires on the GPS tablet on/off pins, with resistors inline to reduce the voltage, and that would probably just have shorted out.

A third problem is that the power button on the GPS actually doubles as a home button. It works like the home button on an iPhone - a quick short press and it takes you back to the home screen from the app your in. Which is useful for changing the contrast/brightness of the screen (which can't be done in the actual sat nav app). And if we did use the motor to power the button, using the tilt button gives a short, sub 1 second, feed so it'd keep kicking you out the app back to the home screen. Soooo.....

Next plan was simply extend the press button and move it to an accessible location. Since we just happened to have a tiny little press button with two pins on it, all we did was run two wires from the GPS pins down behind the dash, fitted the press button in the underside of the dash that houses the TRC and seat buttons, so it's easily accessible and nicely out the way/sight. This works fine, but just means I have to manually turn it on and off, but at least I keep the home button functionality.

So, that was done, it was all connected up and refitted in the car, and here's the last couple pics (and obligatory video)

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https://www.youtube.com/watch?v=KXVyoVlOF_8

Next up, order a new GPS tablet with an AV input, and a reverse camera, and install that. Have an idea about modding the wiring behind the dash a little bit - use one of those JST connectors on the press button switch so that that panel can easily be removed form the car, and on the other end, wire it into a 4pin ATX connector - the other two pins of which can be the + and - from the 12v USB adapter. This way I only have two plugs to disconnect to remove the entire thing - the OEM nav plug and the ATX plug. From the other part of the ATX plug, just run two wires for each the on/off and USB (4 wires total) inside the housing, but also put another JST two pin plug inside so that the on/off be disconnect able. This would mean to remove just the tablet, I can pop off the housing top cover, disconnect the on/off JST plug and pull the USB plug from the PCB, and slide the tablet out. And to remove the entire housing with everything still inside and connected, just undo the ATX plug and OEM plug.

But that's a story for another day.......

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Sparkystav

04-02-2022, 01:48 PM #3

Nice write up mate, and it does look an excellent fit

Read my thread here: The Evolution of my Turbo Lexus from NA-Supercharged-Twin Turbo-Massive Single
Please leave your comments.

OutlawJapClub Admin Team

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Matt_C

04-02-2022, 02:53 PM #4

Thanks Stav - I didn't mean to waffle on as much as I did, but I thought I'd try to include as much as poss in case it helps anyone else!

And I couldn't, and wouldn't, have done this had it not been for this forum in the first place Wink

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Matt_C

04-02-2022, 02:55 PM #5

PS, could you fix the image tag on the second pic in the first post, please - just noticed I didn't tag it properly so it's not showing as a pic

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Sparkystav

04-02-2022, 09:29 PM #6

Done mate.

Read my thread here: The Evolution of my Turbo Lexus from NA-Supercharged-Twin Turbo-Massive Single
Please leave your comments.

OutlawJapClub Admin Team

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Matt_C

05-02-2022, 12:00 AM #7

Cheers dude ��

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