yes, i modified the USB cable from the dock to be an OTG cable.
started the chasis for all the tablet support components. this will bolt in place of the 1.5 din factory radio, behind the tablet.
the top holds the power supply, and hopefully can also fit the BlueTooth adapter, line-driver, and OBDII interface:
the bottom holds the USB hub and all the power distribution blocks (chasis ground, +batt, +ign, regulated +5v, regulated +12v):
i am able to connect everything through a single radio harness - constant and switched power, audio out, amp turn on, and even OBDII (since the radio PCI bus is connected in with the DLC bus).
since in OTG mode the tablet provides power over the USB cable, the hub was staying on even when it's power was cut. i didn't want this to happen as it would drain the tablet's battery when the vehicle was off.
to fix the situation i cut the +5v power wire (red) in the OTG cable. however, then the DLink hub wouldn't fully come on even when it had external power. seems it waits till it sees the +5v from the uplink port... so to fix that i bridged the external +5v to the uplink power pin. again, this is only safe (or necessary) because i severed the power connection in the OTG cable.
the M3-ATX power supply is a little too intelligent for this application. in order to come all the way on, it expects a signal from a motherboard. this is a standard ATX power interface thing, a motherboard usually acknowledges that all is good and it's receiving power by grounding the PS_ON pin.
since i have no motherboard in this project, i simply placed a jumper between pins 14 & 15. this did allow the power supply to come on and give me the +12v and +5v power on the drive power cable that i wanted.
i set the supply's jumpers for it to shut down in 5 seconds (after ignition off). what i didn't realize was that only sends the motherboard the shutdown signal after 5 secs. however, since i have permanently jumpered the PS_ON signal, the supply actually doesn't shut down till the "hard-off" setting, which is 90 seconds.
this all just means the tablet won't be able to start a tasker action to pause music, turn the screen off, etc. until at least a minute and half after the vehicle is off... a little longer than i wanted.
still have a lot to do, but i did get the chasis and tablet mounting all worked out...
also set the wallpaper to be a picture from the front of my Jeep:
cross posting from another forum regarding what apps to use for off-road & on-road mapping:
using BackCountry Navigator for now. i've also tried ViewRanger, Orux, and Trimble MyTopo. BCN had the best handling of large datasets, and a decent interface (but not great). it still crashes when trying to download a really large area at a high zoom level. i have a support ticket in and the developer is working with me on it. their first response was that it isn't meant to do that (download a whole state at zoom level 16 ;)). i explained that there is currently no good solution for overland users and that there is a market for it. one good thing is that it lets you use the microSD card for map storage (which some apps don't). i've read that the XOOM is will support a 64GB microSDXC.
Orux Maps is actually by far the most mature and feature-rich GPS app out there, but it will only let you download maps in 512MB chunks and has no paid-for map source option. it also gives you no visual way to see what you already have downloaded so there is no easy way to piece together a whole state.
i really wish Garmin, Delorme, or National Geographic would release a topo app for Android. they seem to be the only players with vector based topo maps. until then, we're stuck with raster maps which take a long time to download and take up a ton of space.
for around town maps, traffic, and navigation, i'm using Google Maps since i have a 4G device.
when on longer trips where internet service may cut out, i'm using CoPilot Live for my road map and nav software. CoPilot does use vector maps and can download the entire US easily. it can show you alternate routes when doing navigation, speaks directions, has day and night themed maps, and actually does show many small forest roads. i've been using CoPilot with my phone for a while and it's only given me a completely wrong route once so far (as always, GPS is just an assistant, you still need some sense of where you are going). i also tried Sygic GPS Navigation and thought it was terrible. i have not tried the TomTom app, it's very expensive and only has mediocre reviews.
i've used the tablet twice now off-highway and have not had any problems with GPS reception (with the internal GPS unit).
i had to add a ferrite bead to the hacked OTG USB cable going into the dock. i was picking up so much noise that when the power supply was on the screen self-calibration process was going crazy.
found a bug in CyanogenMod 10.0 for the XOOM CDMA (Stingray)...
the /System partition is too small. therefore GAPPS doesn't completely load (but fails silently). this prevented a couple dependencies from being on the system that Tasker needs. i was getting the error when trying to install Tasker that it "requires unavailable shared library com.google.android.maps".
the 2 files that i was missing were:
i ended up having to delete some stuff from the /System partition to make room. mostly there were some videos in the /system/media folder. i also killed the cyanogen wallpaper app and some ringtones. this got me enough space and now i'm up and running with Tasker.
hopefully CyanogenMod fixes this when 10.1 reaches the stable release.
first pass with the electronics is complete and it all works! i'm 90% there in less than a week and a half, this is going way better than my last car pc project! woot!
alright, back to reality, there are plenty of details left still. i did set it in temporarily and go for 2 quick drives today though to make sure things weren't going to completely stop working. the basic Tasker actions for when the car is on/off are working, audio works (BT re-pairs correctly), multiple mapping apps open at the same time sharing the GPS correctly, etc.
High Priority ToDo:
- track down some noises in the audio
- verify all mounting is secure enough for offroad use, then paint all the bare aluminum
- get steering wheel remote buttons working
- purchase an OBDII app and test
- refine Tasker actions to automate even more of the behavior and work out any bugs
- tweak all the app's settings to get things just right for daily use
- improve setup for night use
- future enhancements like external sensors, remote management, multiple cameras, etc.
3 noise issues, one solved already:
1) when i turned the Jeep off, the amp stayed on until the M3-ATX supply finished it's shut-down procedure. during this time there was a slight hum and a ticking sound. i assumed it was something in my setup and spent too much time trying to isolate it. then i finally removed everything that was new and just manually jumpered the factory amp's remote turn-on lead... noise still there! seems i hadn't introduced the noise, i had just enabled a new condition that exposed it (amp on while Jeep off). i tried grounding the negatives on the amp inputs, adding ferrite to the power and turn on leads, etc... couldn't fix.
so i needed to just make it so that the amp went off with the Jeep. i used a relay for now so that the amp is only on when the M3-ATX anti-thump signals it AND the ignition is on. i'd prefer to just modify the M3-ATX to turn off the anti-thump lead whenever it senses the ignition off condition, but not sure if that's possible. i have an email in to Mini-Box to find out more regarding programming custom settings via the serial connection.
2) i have a really loud hum and some popping right after startup. i finally isolated it to the tablet's own CDMA and WiFi radios! it's the proximity of the tablet to either the BlueTooth receiver or the line-driver. if i undock and move the tablet away from the support electronics, i can flip on 4G and/or WiFi and not get the noise... as soon as i move the tablet near my electronics and flip those features on, i get the noise. it only happens for a few seconds right when you turn on either feature, but my Tasker action was turning both features on when the Jeep started. i temporarily removed that part of the Tasker action.
i'll first try to devise some shielding and if that doesn't work then i will try moving the audio components to the rear of the chasis and that might be far enough from the tablet.
3) there is also very, very slight hiss when no music is playing. it's either a grounding issue or maybe the actual touch-screen circuitry in the tablet - i can barely even detect it, but it does decrease volume when i touch the screen. it's so slight that i could probably live with it, but the perfectionist in me wants to fix it.