yashsingh1/xdaforums huggingface dataset:
[G Tablet General] twistedrotors:
I'm not sure why U39 was referenced. Were the GPS serial port pins, TXA (pin 4) and RXA (pin 5), traced to that location? Or was the original author of that diagram guessing about U39?

The GPS module spits out NMEA sentences on TXA in a "serial" format. IMO, I don't know why there would be a need for any sort of hardware converter.

I am concerned about the software side though. By default the GPS module outputs NMEA commands at 9,600bps, 8 data bits, no parity, and 1 stop bit. If the micro isn't setup to accept the messages at that rate then we will have an issue. There is a command to change the serial port settings but I guess we can cross that bridge if we come to it.

-John

Edit: Here's a link to the GPS modules datasheet directly from the Linx website. http://www.linxtechnologies.com/resources/data-guides/rxm-gps-sg.pdf The link provided on Digikeys site doesn't seem to work.
[G Tablet General] twistedrotors:
Warranty voided!

So I cracked open my Gtab because I wanted to see if there was power on the voltage regulator pads of the GPS power section. And there is! U29 has 4.94vdc on it's input pin and U22 has 3.29vdc. What's interesting is that these voltages are present even when the tablet is powered off.

U22 is the power supply that is tied to the GPS's backup battery supply pin. For U22 to always have power makes sense, it's providing the power that the GPS needs in order to keep it's memory and RTC going. This allows for faster Time to First Fix, according to the datasheet.

But U29 provides the main VCC supply voltage to the module on pin 12. If it's always on, then the module will always be powered up. I wonder what that will do to battery life. The module is designed to operate automatically in different power saving modes so the difference in battery life may be negligible.

-John

Edit: Next, I want to figure out what capacitors are needed for the regulators.
[G Tablet General] fosser2:
Holy crap! this is some serious progress. I was not expecting this right now :p I'm really happy that there is power right beneath the gps but the thing that I am concerned about I guess is, is it worthwhile to try to rebuild the power supply circuit, or just run 3.3v from the mini PCI e. I guess I'm down for rebuilding the circuit because its the way it was initially intended to work.
[G Tablet General] rajeevvp:
According to the TnT v1.1 kernel patch file from Viewsonic, enabling and disabling the GPS module (the comment in the driver mentions it is for a "MALATA_SMBA1102") is all that the kernel driver does. No code to anything beyond that. Are there any data lines connected from the GPS and where do they go on the gTablet board. Is it connected to an internal SDIO bus?--You can get GPS data that way.
[G Tablet General] IamGoo:
OK, silly question, BUT if you can simply buy a GPS receiver and download a couple of programs to get a working GPS in the Gtablet, WHy OH HY spend all this time and extra $ integrating it?? Is this more of a "ha ha look what we did, cool" type of thing??

Not complaining, and I certainly don't have the skill to do most of the stuff you guy do so I'm just asking out of curiosity.

Thanks

Brent
[G Tablet General] Synman:
You don't truly own something until you void its warranty ... xda moto
[G Tablet General] tenet420:
@iamgoo

Why carry around another piece of electronics? As it is, I carry a phone, tablet, and laptop in one bag and a digital SLR, HD camcorder, and chargers for everything in the other. I personally don't need an external gps module I've gotta keep track of as well.

Again, thank-you everyone involved in figuring this out...

Sent from my Droid
[G Tablet General] twistedrotors:
Basically, yes. The module I'm using has it's own ceramic patch antenna mounted on it. I haven't said much about it because well, it doesn't fit inside the Gtab. The only location it might fit apparently blocks the antenna too much and causes me to lose GPS lock.

I have a second module (also with it's own antenna) that may fit above the screen with a little hacking of the case. It would only have the plastic bezel covering the antenna so it should be able to keep a lock. I may or may not try it. If I do then I'll let everyone know how it goes.

It looks like Fosser has figured out his antenna placement so that is definitely the way to go.

I do. It's pretty cool! :)

-John
[G Tablet General] twistedrotors:
Wait, you can use an external bluetooth GPS? I had no idea. ;)

Seriously though, it is kind of a silly question. Why, as your first post on XDA, are you asking it? The benefits are obvious and the first post states the OP's goal.

This project has been a lot of fun and I'm glad I could contribute. It hasn't cost me a cent and I enjoy hacking electronics. Yes, I am very cool. :cool:

Again, a huge thanks to Fosser for kicking this off and seeing it to the end! Let me know if you need any help with the guide.

-John
[G Tablet General] fosser2:
To all who are now following this quickly growing topic:

Yes the gps chip works great! Thanks for all of the help that I have received so far in this project. I am not yet done with this project due to the antenna. The gps works great with the back case off, but is still having some issues getting a lock when the back case is on. Hopefully tomm, (monday) I have a antenna extension cord coming. I will be soldering this to the antenna and extending where the antenna can be placed. There is a section of plastic to the right of the wifi antenna that should work the best. I will keep everyone informed on how this helps the gps reception. Another note: the first position that I posted with pictures and stuff does work. If you just have a standard antenna and do not want to attempt an antenna extension this is where I would recommend. I just want the best possible spot for this antenna. Any other antenna locations that people find should please post. I want to "discover" the best possible one. On a final note I will be writing a tutorial as I keep mentioning. It will be a few days before I have the proper pictures and it is complete. (I am just starting summer jobs) So please bear with me. To all of you who are quickly ordering parts: please be careful while soldering in these components. You could easily mess you tablet up doing this project and I would hate to see any posts of someone messing up.

PS: before telling yourself that the gps is not locking properly. Please go stand in the middle of your backyard and wait, most likely you will get a lock.

-Andrew
[G Tablet General] mike_ekim:
Life is a journey, not a destination

Lol you've garnered a lot of attention with that post. :)

Let's ask a broader question: why do anything in life that takes effort or expense, if something similar can be done with less effort or expense? Oil paints and canvas are expensive; why paint a landscape that will never sell for as much money as you invested in it, when you can just snap a picture? BY painting the landscape a painter will experience painting first hand, learn painting techniques, and then be able to share his/her experience and knowledge with other people who want to paint or are just curious about painting.

By getting an external GPS, you get to experience clicking your mouse button and saving $15.

Some people like to challenge themselves, learn new things, and contribute to the general knowledge base.
[G Tablet General] IamGoo:
"Lol you've garnered a lot of attention with that post. "

I certainly did:)

I am nothing but envious for the skills/knowledge many of the folks have here, and I'm forced to glean/steal what information I can from them because of it. I guess for many of the people this is a "hobby" they enjoy, and that's the way I should look at it.

"Some people like to challenge themselves, learn new things"

I guess so, it's the pride of completing a project, and improving(greatly) a mediocre product..... it's because of this site I got my Gtab, and have Vegan running great on it, I never want to be a member of the "Apple" cult.

Thanks

Brent
[G Tablet General] ThatGeekGuy:
A hearty thanks and congratulations to everyone who brought this to fruition, this is fantastic. I'm going to get my parts on order soon, just want to verify something from jmdearras recent list. There are 11 line items in the list, is the number next to the line item the quantity required?

This is going to be fun :D....
[G Tablet General] manikin13:
Thanks for the update John, looks like the separate antennae is the current way, I wish there was a good zpad picture showing how the setup was assembled (antennae placement). Doesn't really make a significant difference as I will glad to be excluding the bluetooth gps from my travel collection. :)
[G Tablet General] jmdearras:
Don't use my list as absolute. I ordered extras as I hate to lose a single part and be stuck until a new one comes, and I ordered two kinds of ferrite beads.

Jim
[G Tablet General] rajeevvp:
I don't want to be a killjoy, but, we may not be out of the woods yet.

Replacing the libgps.so from the Notion Ink Adam firmware works on VEGAn-5.1.1, and I suspect also will on other Froyo-based firmwares like TnT-Lite, but, we haven't tested on any of the Gingerbread-based distributions.

Anybody care to test on a GB-based ROM? I would prefer CyanogenMod 7.0.3, because that's what I'm running, and because I can look at the source on github.com.

I'm just worried that we know what works, but, we don't know why it works. I don't like to tell people, "Sorry, stick to a Froyo-based ROM for this GPS."
[G Tablet General] fosser2:
Well I have the worst news possible. My tablet is totally broken. I have no idea what happened. I was soldering in a few new chips that came today. I soldered in 2 (445-4978-1-ND) at locations C355 and C347. I also installed a new regulator at U22 (I wanted to get rid of the jumper there). After I had soldered in these components I went to turn my tablet back on and nothing happened. Nothing will appear on my screen at all. When I try to NVFLASH I hold down power and vol-. The USB does initiate on my computer so it sounds like it is working. When I try to flash a ROM here is what happens.

D:\Student Data\Desktop\Tablet Stuff\NVFLASH\FORMAT>"nvflash.exe" --bct gtablet.
bct --setbct --bl bootloader.bin --configfile gtablet.cfg --create --go
Nvflash started
rcm version 0X20001
System Information:
chip name: t20
chip id: 0x20 major: 1 minor: 3
chip sku: 0x8
chip uid: 0x1714118843fff557
macrovision: disabled
hdcp: enabled
sbk burned: false
dk burned: false
boot device: emmc
operating mode: 3
device config strap: 0
device config fuse: 0
sdram config strap: 0

sending file: gtablet.bct
- 4080/4080 bytes sent
gtablet.bct sent successfully
downloading bootloader -- load address: 0x108000 entry point: 0x108000
sending file: bootloader.bin
| 928945/928945 bytes sent
bootloader.bin sent successfully
waiting for bootloader to initialize

It just sits here...

I have taken out the 2 capacitors that I soldered in but I did leave the chip at U22. (I don't think this is wrong). Most likely I have f***ed up my tablet completely and waving goodbye to this scene. If anyone has any ideas how to fix it let me know.

-Andrew

-PS: I did not overheat any of the solder points I put in today. Also I have no idea if the tablet got static damaged. I did not shock anything while I was working though.
[G Tablet General] fosser2:
PLEASE READ THIS !!!!!

If you are buying parts for the GPS:

DO NOT BUY

Part# MCP1700T1802ETTCT-ND. I have no idea why, but it causes the tablet not to boot. If you have soldered it in already, take it out. I put mine in and the tablet ceased to work, but as soon as I pulled it out...It worked again. Again there is no official parts list yet as this is still a work in progress.

Not Correct. If you are in the middle of the project, use a jumper to get VBACKUP to work.
[G Tablet General] fosser2:
Since the antenna extension cord was also the wrong part (do not order part J10037-ND) I will be relocating the antenna.

I will post pictures of this mod later tonight, but lets just say that it is a SERIOUS modification. The good news is that it will work with the stock antenna cord and should provide the best reception possible for the antenna. :D Give me about 30 more minutes and it will be installed.

Here is a sneak peak :p
[G Tablet General] twistedrotors:
Good point.

Yikes!! Very sorry to hear about the scare and I'm glad it didn't cause any permanent damage. I looked over the datasheet and checked the pinout again and I'm unsure of why it's not working. The jumper seemed to work fine though so lets just make an executive decision and stick with that.

The antenna looks good. Let us know how the reception is when you get it tested.

-John
[G Tablet General] fosser2:
I'm gonna have to say I'm pleased with the way this project is turning out so far. I just took the tablet for its first "spin" around town. I was using the gps program CoPilot Live. It worked out perfectly, aside from the person talking not being able to pronunciate streets correctly :p
[G Tablet General] tenet420:
@fosser2

Just noticed you are in Wisconsin- I am as well. Nice work here. I'm waiting for your 'finished' tutorial before I give this a go... thanks for the footwork.
[G Tablet General] lanegd01:
I have the Malaga Rom and the bigideas 1222 which have working GPS. I also have the bigideas 3018 which horoscopes the gps.

Let me know if you want them and I will put them in dropbox for a while

Graeme
[G Tablet General] jmdearras:
What pin is the source power on, and what voltage is it?

And the unconnected pin when you jumper is a ground, correct?

Thanks,

Jim
[G Tablet General] jmdearras:
I have been over the specs on the GPS and the regulator. as far as I can see, it should not have caused any trouble. If you installed the 1uf caps backwards, that would have been a problem, and quite possibly running the regulator without it's filter caps could have caused it to oscillate. Or the part could have been damaged.

But from the specs on the GPS chip, it's not really needed. I will install my regulator first, and test for correct operation, to verify all this. Parts arrive Friday.

Jim
[G Tablet General] fosser2:
Honestly, maybe it was a faulty part? i have no idea. If everyone says that it should work than maybe it does? Let me know when you get your parts.
[G Tablet General] manikin13:
Fosser2,

You mentioned using the gps for a trip around town. Was it a long enough test to determine battery life effect?
[G Tablet General] gierso:
Hey fosser2 congrats for the success now ifeel more confident to folliw instructions to doitmyself

Checking what parts to buy now ;)
[G Tablet General] fosser2:
Jim[/QUOTE]

Ha, no sorry I was not watching the battery life. From what I've seen during testing the battery holds up surprisingly well. Imo, I would say that when you are out and about with the tablet you are not connected to wi-fi. Meaning you are really now wasting any more battery. I would say that the tablet wi-fi = gps. So you would get the same hrs of use if you were to use your tablet constantly with the screen on and wi-fi. This is just a guess :p
[G Tablet General] jmdearras:
I would add that before soldering the bare pads, use an ink eraser, or pencil eraser if you don't have an ink one, and rub the pads to clean and brighten them so they take solder evenly.
[G Tablet General] jmdearras:
Oh, and add to step 1, UNPLUG THE BATTERY! :eek:
[G Tablet General] fosser2:
Haha totally good call, I was totally gonna do this and I forgot.
[G Tablet General] clemsyn:
Wish I had soldering skills like you guys :)
[G Tablet General] fosser2:
haha, honestly I don't have much for soldering skills. I knew very little before attempting this project :D
[G Tablet General] -+Bert+-:
Great job guys! Do you plan to restore the mini PCI slot?
[G Tablet General] tgruendler:
Congratz on getting on Engadget with your writeup!!!!!!

http://www.engadget.com/2011/05/25/add-gps-to-your-viewsonic-g-tablet-and-test-your-soldering-skill/
[G Tablet General] fosser2:
I'm pumped that we made Engadget!!!!
[G Tablet General] fosser2:
Ha, most likely not on this one. I guess there are not that many devices that support a slot like this aside from a 3G card. I do not want to pay monthly fees for my tablet so I'm skipping the whole 3G thing.
[G Tablet General] dzasta:
wow i totally forgot about this thread until I found it on engadget!

i have to give you credit fosser2 for diving in head first. glad there were no bga's to install. this is certainly something I will do in the future.

a couple of things: all of the "optional" caps you mention should be put down. the 0.1uf and 1.0uf caps are all decoupling caps used to regulate voltages and reduce noise. who knows, maybe Gmaps and Gearth will work?

as for the 1K resistor you shorted out, it can be one of 3 things. a series resistor to limit current, a pull up resistor, or a pull down resistor. Chances are its one of the later two. Its not the end of the world to short an I/O pin to Vcc or GND but it is not common practice and tends to lead to long term chip reliability issues.

after all of soldering youve done, whats a couple more 0402 placements? (OK the 0201's aren't going to be fun but still).
[G Tablet General] Darth Bagel:
I suggest a current limiting resistor in series with your lock indicator LED.
[G Tablet General] fosser2:
Google maps works fine, I have not tried google earth but I'm sure that works fine too. As for that resistor I'll look into it. Thanks for the heads up.

The output of the lock line is outputting a very small voltage, why is a resistor necessary here? Sorry, I'm just wondering.
[G Tablet General] gierso:
Stupid Digikey it doenst allow me to add the gps module to the cart.. (i live in mexico and the problem is related to customs :( )

looking for other dealers xD ;)
[G Tablet General] gierso:
some times voltage can be as low as 3 or 5 volts, but the current can toast things if not limited :P
[G Tablet General] gierso:
yes the photos show that .. ;)
[G Tablet General] gierso:
maybe a compass, tv card xD (sorry just kidding on the last One)...

or maybe the GPS has a compass i dont know

here is the module datasheet

http://www.linxtechnologies.com/resources/data-guides/rxm-gps-sg.pdf

it say something about Nemea examples putting North south west east

can u try a compass application :) ????
[G Tablet General] gierso:
i wish i had any programming skills like u :)
[G Tablet General] descreetion:
map app

In terms of map applications, has anyone tried MapDroyd (and its counterpart ContentDroyd)? Apparently it can download map files for offline use. Granted it doesn't have street turn-by-turn navigation, but does use GPS and looks like it has compass functionality (can you work on that fosser :P). I think this would be a good app to try with this mod.
[G Tablet General] fosser2:
I will be re-uploading all of the pictures to a different file hosting. Sorry about the photobucket pictures. That will be the last time I use their service :p
[G Tablet General] Childofthehorn:
YESSSSSS!!!!! Finally have a worthwhile use for my rework station.

Thanks for the part numbers. I am adding these parts to my current mouser/digikey orders!

BTW - the best way to solder this stuff cleanly is to use solder paste, but you can do it like the method you posted.

The best way to do this with an iron is to tin the pads and then clean with a solder wick.

Then, put flux paste thinly on the pads ( I like kester flux paste because of its consistency).

Lay out your components on the board and once you have it in place solder JUST ONE PIN.

There you can adjust by just reheating the pin until straight.

From there, soldering the rest of the pins is easy.

For the lazy folks, buy some solder paste, put it on the pads, lay down the components, and heat with either a soldering iron or a rework air gun.

Using either technique, clean off the flux with Acetone (nail polish remover) as denatured alcohol takes forever and acetone doesn't have any issues with the components on the board I have seen.

This will result in perfect board construction.
[G Tablet General] twistedrotors:
Nice!!! Congrats Andrew, you lead this project like a champ!
[G Tablet General] fosser2:
Ok, all of the pictures from the tutorial are now relinked to a different image hosting. They claim that there is unlimited bandwidth, so I guess we'll wait and see :p

I also need a volunteer to try this mod using a different android 2.3 based rom! please speak up :p
[G Tablet General] m_elias:
U29 is described as a 5vdc VCC Reg but the part number (NCP551SN33T1GOSCT-ND) and link shows a 3.3V output (up to 12V input) Reg at digikey. U22 also shows up as a 1.8V Reg, not a 3.3V. Please clarify. I'm looking forward to trying this mod. Thanks.
[G Tablet General] gwynethgh:
Between the digikey and Radio Shack parts I see a total of 60-70$ if anyone else wants a ball park estimate.
[G Tablet General] fosser2:
John will have to correct me if I'm wrong on this one, but if I remember correctly: approx 5v is going into the 5vdc VCC Reg and it outputs 3.3v to the GPS chip. I am guessing that there is 3.3v going to the other chip that runs VBACKUP. The "backup" pin on the chip basically just has to be enabled to turn it on, so it doesn't take too much voltage.
[G Tablet General] twistedrotors:
That is correct. The regulators should be referenced by their output voltage though, not input. That's probably where the confusion is coming from. A bit of a technicality. :p

-John
[G Tablet General] gierso:
so fosser2 do you know if the gps module has compass or if it can be added? :):rolleyes:
[G Tablet General] fosser2:
I have been looking for like an hour on this subject. Honestly the conclusion I have come to is that I'm not sure. I have read a bunch of different reviews saying that it does have a digital compass and that it doesn't. People seem split on the issue. Directly from Viewsonic's site "Compass support for Google Maps." Here is the link: http://www.viewsonic.com/products/gtablet.htm. I am going through chip by chip on the mainboard currently and seeing if there is a digital compass chip built into it. I can verify that compass applications DO NOT work. (I have not tried them w/ gps running)

EDIT: there is not documentation on a lot of the chips on the board. That really sucks.
[G Tablet General] cranky_dan:
Wow. I am excited to be able to try this. NICE JOB with the tutorial. Good work to you and all that helped make it happen.

I am looking forward to hearing about battery life...

Dan
[G Tablet General] rajeevvp:
Viewsonic should've included the complete sentence instead of truncating the original, which reads:

Do a search on "Compass ..." and you'll find a lot of links to the original, all of which announce the new features to be found in AOSP Froyo. Apparently this was a new functionality that Google added to the browser in Android 2.2.

Plus, the TapNTap kernel patch from ViewSonic has no code at all to support a magnetometer (AKA digital compass).
[G Tablet General] fosser2:
But the real question, does the tablet have the chip built in, but just not coded in?
[G Tablet General] fosser2:
For all of those who have been waiting for a battery update, I have posted it in the tutorial. You're all gonna like the final results!
[G Tablet General] rajeevvp:
ViewSonic seems to have taken the nVidia reference design and then got Malata to gut it pretty thoroughly to make the gTablet. I would be very surprised if it was built-in.

Some commercial GPS receivers can show you the compass heading, but, this seems to require 2 or more antennas.

I looked at the pdf specs for the RXM-GPS-SG module that was posted in this thread, and there seem to be 2 NMEA strings which could provide compass heading data directly. Unfortunately, this module does not seem to provide those values. Look at the RMC and VTG NMEA string tables on page 14. All the compass-related fields are marked as "Not Available".

If you are looking for ideas for your next project, take a look at this thread posted just today. There's even a reward:

http://xdaforums.com/showthread.php?t=1099119