GPS Problem (No, it's NOT the Flexcable!)

[thezock]

Hi.

Some time ago i got my hands on a Moto A780. In the time between i bougth it and i send the money the seller told me that gps was not working and he offers to reduce the price. I thought that this could not much be an issue (reflash or just reset an things will work again) and bougth the phone.

The phone arrived and as i was told the gps-entry was missing. I only reset the phone (thru the settings menu) and voila, the gps was available an also copilot worked. Phew, that was easy. Happy happy joy joy. But not for long. Just a week later the gps-symbol on the mainpage was crossed red again and i was not able to activate gps. Heck, okay, one more time to reset. But i wasn't successful this time! Nothing changed.

Time to search the internet for solution. On 95% the pages i read that a broken flexcable is the cause for this mess. Okay i thought, 95% can't be wrong, so i looked for a flexcable. Great, i found one in Hong-Kong. Moderate price and moderate shipping. It just took what the original seller reduced in price for the broken gps. Things will be finde i thought.

Weeks later i now was able to find time to replace the flexcable. I opened the phone, removed the "old" cable. As i was reviewing the old cable i was not able to see even the lightest problem. No scratches, no cracks, no nothing. But who cares, i have a factory-fresh new flexcable, so i put it in.

At last i managed to get the phone together again without any broken parts. Power on... loading...Phew, i did not break anything. GPS-Symbol? Red crossed! Damn!

I tried to reset the phone again, no result. Allways the GPS is crossed red.

I did not change the Firmaware-Version at any time. The GPS WAS working for about 15 Minutes when i reset the phone for the first time.

What else could be the cause?? On hardwareside i only replaced the transflash-card with a somewhat bigger one (that hold's some mp3's and is working). On Softwareside i only resetted the phone, no more.

And ... NO... It's not the flexcable...Really, trust me, it's NOT NOT NOT the flexcable. 95% were wrong!

<Guido>

[thezock]

No Idea anybody?

No way to investigate the problem?

<Guido>

[swifty]

i have never seen such a problem
maybe the GPS-chip is defect.
the GPS problems i have seen are all been solved with replacing the flexcable.
Mozilla/5.0 (X11; U; i686 Linux; en_US; rv:1.8.0.4) Gecko/20060508 Firefox/1.5.0.4

[thezock]

I just have seen some interesting behavior.

I loaded the bat and while doing that i did a master reset. After the phone rebooted the GREY gps-symbol was displayed and i also was able to activate the gps. As i tried to start copilot and wanted to go out of the appartment the gps symbol changed to the red-crossed again.

I retried the master reset and after the reboot the red-crossed gps symbol was displayed. As i also read on some site that the gps seems to neet a quite high voltage i thought that it could be the bat that is not quite okay.

So i hooked the phone back to the charger and did another master reset. I thought that the grey gps-symbol would display, but, it was the red-crossed

GPS is really a mess with that phone

[Kuddel]

I am facing a similar problem with my phone. I can switch gps on and off in the menu, but I will get no signal, neither with copilot nor with bikeator. The gps symbol stays in light grey all the time (no flashing from grey to black). I reflashed the phone with the 76er firmware and made a master reset and I killed lapisrv, deleted the pid an socket file and restarted, but all that did not help at all. I replaced the flex cable twice and the first time it brought my gps back for 20 minutes but after restarting the phone I had the same behaviour as before. With the second flex cable replacement I had no gps at all. The on/off switch in the menu disappeared and on the idle screen I had the red-crossed gps symbol. Switching back to the first replacement flex cable brought at least the light grey symbol back, but I still get no signal ...

[Halftux]

I don't know if this is useful. However the gps chip has two ports at same pin spi and uart. Maybe its not in the right mode. I dont know if this could happen, maybe when it was active and lost the power. Normaly i would say after wake up it should selfreset.

There is also a reset testpoint on the mainboard near the flex connector.

TP_GAM_RESET

GAM stands for GPS Acquisition Module.
Maybe you could reset the chip. But it also could be that you clear the firmware from the MG4100. No risk no fun

Or you can compile chat for the phone and try send at commands to the gps and see if you get a response ( /dev/mux [multiplexing device]).

These documents could be helpful if you like to analyse if the gps chip is dead. However I cant give you instructions because I never had this problem. If it is fixable you need to find a way.

http://www.motorolafans.com/forums/a...html#post17945

http://www.motorolafans.com/forums/a...ce-manual.html

good luck

Or buy a used one

[Halftux]

I tried to get some communication with /dev/mux14 by using echo. Also i played with cat < /dev/mux14 and gps on off switch. Did not get any response only with cat i get somthing like this "P xP"
After lot of testing my GPS couldnt switch on again or could not switch off again and the phone hangs at shutdown. After removing the battery and switch the phone on again the gps works like before.

If the GPS is on you could get the configuration with:

stty -a -F /dev/mux14

You can also test the communication with a test_gps program.

http://www.motorolafans.com/forums/d...html#post15988

So i could strace the communication with:

./strace ./test_gps /tmp/lapisock

[Kuddel]

Hi Halftux,
thank you for your help. stty on /dev/mux14 tells me:

# stty -a -F /dev/mux14
speed 38400 baud; rows 0; columns 0; line = 0;
intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = <undef>;
eol2 = <undef>; start = ^Q; stop = ^S; susp = ^Z; rprnt = ^R; werase = ^W;
lnext = ^V; flush = ^O; min = 1; time = 0;
-parenb -parodd cs8 -hupcl -cstopb cread -clocal -crtscts
-ignbrk -brkint -ignpar -parmrk -inpck -istrip -inlcr -igncr -icrnl -ixon
-ixoff -iuclc -ixany -imaxbel
-opost -olcuc -ocrnl -onlcr -onocr -onlret -ofill -ofdel nl0 cr0 tab0 bs0 vt0
ff0
-isig -icanon -iexten -echo -echoe -echok -echonl -noflsh -xcase -tostop
-echoprt -echoctl -echoke

and cat shows that (started bikeator before doing cat on mux14):
# cat < /dev/mux14
PÿÿÿÿÿÿÿüÏ°PÿÿÿüÏ°Pp
ÿÿÿÿÿÿÿüÏ°PÿÿÿüÏ°Pp
ÿÿÿÿÿÿÿüÏ°PÿÿÿüÏ°PpÿÿÿÿÿÿÿüÏ°PÿÿÿüÏ°PpÿÿÿÿÿÿÿüÏ°PÿÿÿüÏ°PÿÿÿÿÿÿÿüÏ°PÿÿÿüÏ°Pp
ÿÿÿÿÿÿÿüÏ°PÿÿÿüÏ°Pp
ÿÿÿÿÿÿÿüÏ°PÿÿÿüÏ°PpÿÿÿÿÿÿÿüÏ°PÿÿÿüÏ°PpÿÿÿÿÿÿÿüÏ°PÿÿÿüÏ°PÿÿÿÿÿÿÿüÏ°PÿÿÿüÏ°Pp

and strace shows the following:

# ./strace ./test_gps /tmp/lapisock
execve("./test_gps", ["./test_gps", "/tmp/lapisock"], [/* 10 vars */]) = 0
uname({sys="Linux", node="(none)", ...}) = 0
brk(0) = 0x10968
open("/etc/ld.so.preload", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/lib/v5l/fast-mult/half/libc.so.6", O_RDONLY) = -1 ENOENT (No such file or directory)
stat64("/lib/v5l/fast-mult/half", 0xbffff19 = -1 ENOENT (No such file or directory)
open("/lib/v5l/fast-mult/libc.so.6", O_RDONLY) = -1 ENOENT (No such file or directory)
stat64("/lib/v5l/fast-mult", 0xbffff19 = -1 ENOENT (No such file or directory)
open("/lib/v5l/half/libc.so.6", O_RDONLY) = -1 ENOENT (No such file or directory)
stat64("/lib/v5l/half", 0xbffff19 = -1 ENOENT (No such file or directory)
open("/lib/v5l/libc.so.6", O_RDONLY) = -1 ENOENT (No such file or directory)
stat64("/lib/v5l", 0xbffff19 = -1 ENOENT (No such file or directory)
open("/lib/fast-mult/half/libc.so.6", O_RDONLY) = -1 ENOENT (No such file or directory)
stat64("/lib/fast-mult/half", 0xbffff19 = -1 ENOENT (No such file or directory)
open("/lib/fast-mult/libc.so.6", O_RDONLY) = -1 ENOENT (No such file or directory)
stat64("/lib/fast-mult", 0xbffff19 = -1 ENOENT (No such file or directory)
open("/lib/half/libc.so.6", O_RDONLY) = -1 ENOENT (No such file or directory)
stat64("/lib/half", 0xbffff19 = -1 ENOENT (No such file or directory)
open("/lib/libc.so.6", O_RDONLY) = 3
read(3, "\177ELF\1\1\1a\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0\344\376\3"..., 1024) = 1024
fstat64(3, {st_mode=S_IFREG|0755, st_size=17592186044416, ...}) = 0
old_mmap(0x41028000, 1252756, PROT_READ|PROT_EXEC, MAP_PRIVATE, 3, 0) = 0x41028000
mprotect(0x4114c000, 56724, PROT_NONE) = 0
old_mmap(0x41150000, 32768, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED, 3, 0x120000) = 0x41150000
old_mmap(0x41158000, 7572, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x41158000
close(3) = 0
old_mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x40000000
mprotect(0x41028000, 1196032, PROT_READ|PROT_WRITE) = 0
mprotect(0x41028000, 1196032, PROT_READ|PROT_EXEC) = 0
socket(PF_UNIX, SOCK_STREAM, 0) = 3
socket(PF_UNIX, SOCK_STREAM, 0) = 4
connect(3, {sa_family=AF_UNIX, path="/tmp/lapisock"}, 15) = 0
connect(4, {sa_family=AF_UNIX, path="/tmp/lapisock"}, 15) = 0
write(3, "Z\1\0\0d\0\4\0\1\0\0\0", 12) = 12
read(3, "\0\0\0\0e\0\4\0\302b\320[", 256) = 12
write(4, "Z\1\0\0f\0\4\0\302b\320[", 12) = 12
read(4, "\0\0\0\0g\0\0\0", 256) = 8
write(3, "Z\1\0\0j\0 \0\0\0\0\0\2\0\0\0\226\0\0\0\226\0\0\0\210\23"..., 40) = 40
read(4,

and at this point it stops, bu that might be because I tested that in my office and there are obviously no gps signals. I'll test that outside later.

[Halftux]

Hi Kuddel,

the strace process shouldn't stop also if you are inside.
Without the source from test_gps it is hard to say where it stucks.
The chip has different power modes. At this point were your strace hangs it waits a little bit at my phone. I think there the GAM and RF get the Power. When the GAM gets the power it will send immediatly some signals also if there is no satellite. So it will only read data and dont send some. In this state the gps symbol should blink. It looks like this:

read(4, "\0\0\0\0\0\0j\0\0\0\0\0\0\0\0\0p>\0\0\0\0\0\0p>\0\0\0\0"..., 256) = 114

I would guess maybe there is a power supply problem could be due to a higher resistance. Also you have different power supply wires maybe there is something wrong. Or a part from the chip is damaged or stuck (think about gam reset). There is also a selftest command and softreset maybe you can figure out how to invoke the communication.
Now you need to measure the voltage to get a clue. You can also try to measure the resistance from your flexcables to exclude if its damaged.

I will attach a document with more information with these power modes.

However i think it will take some time to analyse all.
Maybe it is really better to buy a used and change the flip or to use an external bt gps.

[Kuddel]

Hi Halftux,
it looks as if the is no easy way to bring my gps back to life, if there is a way at all. Yesterday evening the gps was back for 10 min, but it is not reproducible why it worked. This morning the gps was silent again.
You mentioned the reset procedure, do you have an idea how to reset. Do I have to connect the TP with ground at power up or something like that?