Samsung Galaxy S3 LTE and VOIP Microphone Issue

I heard about FreedomPOP from my brother, basically you get 200 minutes, 500 Texts and 500MB data free each month. They use the Sprint network and support 3G & LTE. The way it works is everything goes over the data connection. Calls are routed over VOIP and texts are about the same. This actually works really good for me as I get basically no service at home on Verizon or Sprint, but I have good WiFi. It will route over any available internet connection, so you could even use it overseas (on WiFi). There are some issues I can't resolve ATM. Here's What I've run into so far:

I'm running a SlimKAT 7.0 on a Samsung Galaxy S3 (Sprint), so these may or may not work for you. I TAKE NO RESPONSIBILITY IF YOU BRICK OR DAMAGE YOUR DEVICE!

Problem 1 - No LTE

No LTE, 3g works fine, but when you get an LTE Connection you don't get an IP. This is an APN problem. LTE Works fine on stock, but not on SlimKAT / CM11 (tested).

Solution:  You have to activate on stock (you should have a nandroid right?). After you've got everything working on stock you have to backup your APN list, then flash your custom ROM.
Next you have to restore your APN list, reboot and LTE will work! Unfortunately it's harder to do than it seems. an unprivileged app can no longer write to the APN list. So here's my solution (you may or may not need to do this on stock to read them):

1. Make sure your phone is rooted (and has supersu or something on it)
2. Install APN Backup and Restore from the Play Store.
3. Install ES File Explorer File Manager from the Play Store.
4. Launch ES File Explorer and in the setting enable "Root Explorer"
5. Navigate to "/data/app" and long press and "cut" "com.riteshsahu.APNBackupRestore-1.apk"
6. Navigate to "/system/priv-app" and paste the apk file there. 
7. Long press on the apk and hit properties. Permissions should be "rw-r--r--" Owner and Group should both be "root"
8. Reboot
9. Open APN Backup and Restore, close the ICS warning, hit menu, then disable ICS checking.
10. Now you can backup and restore your APN's

Notes:

• If you're restoring you may want to make a backup, delete the APN's that came with your ROM, then restore the stock ones. 
• You may need to find and move the stock file with ES File Exporer if it didn't save to "/storage/emulated/0/ApnBackupRestore". 
• I don't recall where it saved them on stock, but you may want to find it and make sure it's not going to get deleted when you flash. 
• Reboot when you're done.

 Problem 2 - VOIP Apps use top microphone

I fought with this for quite a while, in the freedompop messaging app I could turn on various settings and it would work until they updated the app, then it would require a different set of options. I thought it was a freedompop problem until I started playing with the new Google Hangouts. It only used the top microphone, and there were no options to fix it.

Solution: It's a build.prop issue.

1. Install Build Prop Editor From the play store. (or use whatever method you want)
2. Change "persist.audio.handset.mic" from "digital" to "analog"
3. Reboot 

Note: I removed some lines in "/etc/audio_policy.conf" related to VOIP before finding the build.prop issue and it didn't fix it. But it may have changed things, I'm looking into this.

UPDATE: Just confirmed from my brother - the build.prop edit fixes the problem.

Problem 3 - Amazon Music Won't Play Downloaded Prime Songs

Symptoms: Streams Prime music fine, plays music I've bought and downloaded, plays MP3's from the phone fine, crashes when trying to play Prime Music I've downloaded.

No solution so far.

Underground Leak Location (Failed, but interesting)

My brother has a water leak in the plastic line between his house and the street. We don't know where the pipe runs and haven't been able to find a wet spot. It's not a huge leak, so he can just shut it off at the meter most of the time.

Cool Little Amplifier

The first problem is locating the pipe, we know where it is on both ends, but there's 400ft and a concrete driveway in between.

Options

• I found ground penetrating radar first, but it would cost way more than just running a new pipe to buy and it's well out of my capabilities to build. Maybe in a few years, but we don't have that kind of time.
• Metal detectors don't work on plastic pipe unless you put something metal in them (steel cable), which requires disconnecting the pipe. If we had a metal detector this would be a reasonable starting point. It's still on the table, but we have other options to try.
• A smaller wire could be pushed down the pipe and connected to a small transmitter. Then a receiver would locate the signal and pinpoint the pipe.
• With a ground microphone and an amplifier it's possible to listen to sounds under ground. A wrench or solenoid can be used to tap on the pipe, which will transfer down the pipe a ways and (hopefully) be audible near the pipes location. The leak may also be audible within a few feet.

Schematic - Pretty much exactly as in the source link

I've build a amplifier based on a circuit for an amplified ear I found on the internet. It seems to work good, but I'm having a real problem with the microphone. It will pick up sounds from all over, but nothing from the ground. I've tried several different ideas to transfer the sound, but so far I've come up dry. I think a piezo buzzer element is the key, and I managed to break the only one I had. I've got several more on the way, but it will be at least Saturday, probably Monday before I have them. We can't start digging before Monday (call-before-you-dig), so I'm hoping for Sat.

Prototype and RevA001 PCB

Results So Far

• It's a really cool little amplifier, Q3 varies the gain of Q1 so that faint noises are highly amplified and loud noises have little amplification. If I can sort out the microphone problem it should work really well. It would also work great as an electronic stethoscope.
• It doesn't seem to work as I intended to use it. I really need the digikey parts before passing judgement, but I think it should have a variable bandpass filter in it to isolate the desired noises. I can hear all kinds of stuff, but not what I'm listening for.
• I ended up connecting a piece of wire to a fish tape, shoving it down the pipe and hooking a arduino clicking a relay that shorts a (low output) battery charger across the wire to transmit a clicking noise. I only had a 50ft tape so I couldn't trace much of the line, but it looks like a bee line. I used 30 turns around a cool-whip container (approx 15cm diameter) connected to the microphone input to listen for the clicks. It (barely) picks up the clicks, but AC lines are VERY obvious (loud buzz). I think I found the pipe and the end of the tape, but gave up as I didn't feel I was accomplishing anything. I could divide the pipe into (up to) 8 pieces and find the leak, but that would mean 8 potential future leak points (and 8+ holes to dig of unknown depth).
• Unless the digikey parts are here tomorrow and I locate and fix the leak (unlikely) we're digging in a new line with a trencher on Monday. It's not looking good. I'm not shelving this project yet though, it would be very useful for locating noises in various equipment and it should work for finding pipes, if I can come up with a working mic. Perhaps I'll modify it for a bandpass filter too. 

Notes

• R1 is specified as 10K, but my mic element specified 2.2K and worked much better with that. For the piezo transducer and the wire coil I disconnected the resistor.
• The audio jack is connected with wires, I didn't have time to make a footprint for the one I had.
• I did the PCB in a hurry, and I really should redo it, I make no promises as to it's performance.

Underside of PCB

Links

Circuit source: http://www.redcircuits.com/Page38.htm
KiCAD Files: https://dl.dropboxusercontent.com/u/4806416/GroundMic.zip