Openmoko - User contributions [en]

User:BlueLightning

2007-07-28T12:09:08Z

BlueLightning:

*'''Name:''' Paul Eggleton
*'''Location:''' Auckland, New Zealand

I'm a software developer and full time Linux/KDE user (well, at home anyway; at work I develop Windows apps). Currently I work on the [http://opie.handhelds.org Opie] project and do a little bit with [http://www.opensync.org OpenSync], but I hope to also contribute something on the applications side to OpenMoko as well. In the past I have done quite a lot of wiki documentation and cleanup work so I will probably do a bit of that here also.

My blog is at http://bluelightningnz.blogspot.com; occasionally it even has something interesting on it :)

Openmoko Local Groups: Auckland

2007-07-28T06:43:00Z

BlueLightning:

{|border=1
!Name
!Skills
!Level of Interest
!Location
!Other
|-
|[[User:Myfanwy|Myfanwy]]
|Hardware engineering, design and manufacture
|User, possibly developer later
|Auckland city
|
|-
|[[User:BlueLightning|BlueLightning]]
|Software development
|Developer (nothing contributed yet)
|North Shore
|
|-
|
|
|
|
|
|}

[[Category:Community]]

Hardware:AGPS

2007-06-07T03:32:24Z

BlueLightning: Minor spelling/grammar/formatting fixes

The [[:Category:Neo1973 Hardware | Neo1973]] uses an Assisted Global Positioning System, AGPS, technology. [[Hardware:AGPS | The Hardware:AGPS page]] provides information on GPS in general and the [[OpenMoko]] chip in particular.

AGPS chip in the Neo1973 is called Hammerhead, and it is the same chip used in TomTom one devices, which incidentally run Linux, too. See [[Hammerhead protocol]].

== Q: Has anybody here ever used AGPS? I'd like to hear your experiences. ==

Everybody who has used a modern GPS has used AGPS. It is usually called warm-start or hot-start. AGPS is purely a marketing term. To calculate the position a GPS chip needs:
* ''almanac'' = coarse position of satellites
* ''ephemeris'' = precise position of satellites

The almanac is broadcast in a loop of 12.5 minutes and valid for at least six weeks. The ephemeris is broadcast in a loop of 30 seconds and valid for ~2 hours.

Time is mostly irrelevant, as modern chips synchronize within a second with the satellites.

The receiver chipsets store this data in flash and load it from there onto the chip in order to _assist_ the hot or warm start.

AGPS now means to load the almanac and the ephemeris from elsewhere, i.e. via a network. For example for free from the American government: http://www.navcen.uscg.gov/gps/precise/default.htm

AGPS is a nice convenience yet the success and proper functioning of TomTom and Navigon PDAs shows that you don't need that at all.

It's worth noting that the GPS on the neo is sensitive enough to pick up GPS signals in buildings.
If the spot you charge your neo happens to have a GPS signal, downloading the almanac from the satellites while it charges is essentially free, and takes no Internet access at all. Do this daily, and you get most of the benefit of aGPS.

== Q: The chip in the Neo1973 is a Global Locate AGPS. Anybody know what type? Hammerhead maybe? ==
A: It is the Hammerhead.

== Q: I understand the concept of assisted GPS. But does the phone have its own antenna/receiver so that it can work without 'assistance'? ==

A: See above, the important part is the GPS and not the assistance. Antenna is thus compulsory.

== Q: Has anybody got any info on the whereabouts of assistance servers, especially in Belgium and Europe? ==

A: They can be anywhere on the net. Alternatively a service from the cellphone operators. However, there may be occasions where you want a server 'near' where you are. See the later question on DGPS.

== Q: Using the assistance servers will probably mean that I will have to pay for that service. Any idea of the costs? ==

A: They use the low cost of their chip as selling point. Their website implies that this is a service that comes with the chip. I'd call it not very clever if they are going to charge you - it would change their image from lowcost to money grabber and the reverse engineering of their binary protocol would happen even faster.

Last but not least: Global Locate boasts itself to get a first fix in 8 sec without AGPS. The importance of AGPS depends whether the part of their website you are reading is targeted at cell phone operators, or not.

== Q: Is there any "A-GPS standard" whatsoever? ==

A: No. It's a broad term for many variants of GPS.

== Q: I have heard elsewhere (Wikipedia) that in A-GPS the computation effort is shared between the device and the A-GPS Server. According to a previous post, the device just downloads the ephemeris table so there isn't any actual "computation sharing", but rather a download of a pre-computed table download. Correct? ==

A: Yes, in this case. In others the server may do more work. For the neo, all the position information is computed in the neo.

== Q: A-GPS involves additional data traffic and thus (potential) additional costs. Does it use a normal GSM/GPRS IP-based data transfer? does it use some out-of-band GSM/GPRS control messages? or does it get data from broadcasts in the local cell (e.g. GSM cell-broadcast)? ==

A: GPRS. so its up to you whether you want that extra traffic (and cost, unless you're flat) or not.

== Q: if the answer to above is GPRS: is it possible to estimate in advance how much additional traffic (in Kbytes/day of full operation)? ==

A: The absolute worst case is 50 bits/s * 12.5 minutes = around 5Kbytes for the full almanac.
However, this is certainly not needed every day.
The errors in orbit prediction when you have a full almanac are quite small over the short term (a week).
5K once (or the GPS on for 12.5 minutes) then .5K/day should be quite adequate.

== Q: Are there any known estimations on the overall (A)GPS performance on the Neo (esp. fix time) ==

A: The Hammerhead brief information page specifies 1s fix time for a position with 5m error.

== Q: Coming to the Neo1973. In order to save costs, can the "Assisted" function in A-GPS be disabled through software API? ==

A: Yes, it can be disabled through preferences.

== Q: Is it possible to tell whether A-GPS is actually in use or not? ==

A: Yes - either you have enabled it in preferences, or you haven't ;)

== Q: Is it possible to tell/know which is the A-GPS server currently in use? ==

A: yes.

== Q: Can choosing to use GPS (even with A-GPS disabled) enable others to track me? Is there a mode where this is not the case? ==

A: The receiver does not emit significant amounts of RF - unless you are literally within centimeters of the device, it's not possible to pick it up. The other alternative would be that the supplied plugin to gpsd is trojaned, and can be asked somehow to report on your position.
The position is entirely computed in the plugin to gpsd, the GPS hardware cannot know it, it's too dumb.

== Q: What is DGPS, can DGPS and A-GPS work together? ==

A: [http://www.oc.nps.navy.mil/oc2902w/gps/dgpsnote.html An overview of DGPS] Differential GPS is basically a way of removing systematic per-satellite errors from various causes (satellite clock drift, atmospheric effects) for 'nearby' receivers, given one receiver that knows where it is.

The per-satellite range errors to a satellite are around 2-3 metres typically. These per-satellite errors are similar for users close to each other.
These corrections are broadcast by radio in much of the USA (which the neo cannot pick up).

If you can download error information from a nearby source, then you can obtain positions that are much more accurate than without this information. Perhaps well under 1m radius of error, instead of 2 or 3. In some applications this may be of use.

It may be that the apgsd cannot do this, and it will require reverse engineering.

In any case, this would be another few hundred bytes a minute while this is active. (the error information rapidly ages).

Any stationary receiver - even a neo on charge, with a good signal, can produce useful error information. If it had a cheap internet connection at the same time, it could be constantly updating a global error model, for use by other neo owners.

It may be that the apgsd cannot do this, and it will require reverse engineering.

=== Q: I thought DGPS couldn't be done like this. ===
See for example http://gpsinformation.net/main/poordgps.htm
A: This is quite different from simply looking at the relative offset of reference GPS device, and a known point, and then comparing.
The difference is that the neo can help to derive (in combination with other stationary devices) a real-time model of the different sources of error. See the last comment on the article you refer to - the neo chip produces pseudorange output, it can be corrected in this same manner.

== Q: Is an open-source GPS daemon able to be distributed by FIC? ==
[http://www.fas.org/spp/starwars/offdocs/itar/p121.htm A web copy of the ITAR - International Traffic in Arms Regulation legislation, currently in force in the US]

While stupid, this defines

----
... GPS receiving equipment with any of the following characteristics:
...
(2) Designed for producing navigation results above 60,000 feet altitude
and at 1,000 knots velocity or greater;
----

as being a munition.
This is right after the section prohibiting rockets that can be used to deorbit satellites on a specific target, and just before nuclear weapons design and test equipment.

And just because it's stupid doesn't mean they won't kick the doors in - or prevent it from sale and levy huge fines, after the gleefull lawyers at Apple point it out. (you need DOD licenses to import/export)

The plugin for the gpsd daemon presumably implements this limit.

Much established hardware has pretty much confirmed that it's OK to do it this way - as long as it's closed source, you can point at the evil hackers, and say that you never did it.

An open source plugin for gpsd distributed with the neo might raise other issues, namely that at some point in the code, there is a self-documented if(velocity>1000kt) test, which can be trivially commented out.
(the hardware must be able to do this, the velocity of a satellite towards and away from the user greatly exceeds 1000 knots.)

If I was FIC, I would at the very least want a good legal opinion on if an open source gpsd plugin (perhaps a user contributed one after decoding the binary stream that the hammerhead puts out) can be safely distributed, before doing so.

--[[User:Morricone|Morricone]] 11:15, 16 February 2007 (CET) You forget, that FIC is not located in the USA, so US laws do not apply.

Very true, however, this would mean that it could not be imported into the US.
Also that anyone from FIC involved in this could not travel to the US without fear of arrest.
The penalties are really quite high.
--[[User:Speedevil|Speedevil]] 14:10, 16 February 2007 (CET)

Isn't this resriction implemented in the chipset? wouldn't the chipset itself be illegal in the US without these restrictions?
--[[User:Kiney|Kiney]] 22:20, 14 March 2007 (CET)

The chipset is too dumb. It does not know the position or the velocity. This is only computed in the host CPU. --[[User:Speedevil|Speedevil]] 06:17, 25 March 2007 (CEST)

[[Category:Neo1973 Hardware]]

Neo 1973 Phase 0

2007-03-12T09:20:47Z

BlueLightning: Typo fix

== Phase0 Quick Start ==

See the following sections for quick start instructions for Phase0 developers:

* [[Bootloader#Phase0_Quick_Start|Accessing the Bootloader]]
* [[Neo1973_Audio_Subsystem#Phase0_Quick_Start|Playing an MP3 file]]

== Software Image ==

We were using u-boot, kernel and rootfs images from http://people.openmoko.org/werner/devirginate-20070301.tar.gz
to pre-install the devices. This is a self-contained [[devirginator]] snapshot, and can be used at any given time to fully restore the phone ('''complete loss of data is implied''').

=== Restoring original Software Image ===

{{note|This is how you do a full restore, including [[bootloader]]. This requires a [[Debug Board]]. In most cases, it is sufficient to use [[dfu-util]] to flash [[kernel]] and rootfs partitions}}

This is how to restore the phone:

* Download [[http://people.openmoko.org/werner/devirginate-20070301.tar.gz devirginate-20070301.tar.gz]] to the Linux PC that will do the installation.

* Go to a convenient directory, then

tar xfz devirginate-20070301.tar.gz

* Enter the directory:

cd devirginate-20070301

* Disconnect everything:
** the USB connector of the debug v2 board from the PC
** the USB cable from the Neo
** remove the battery

* Connect the Neo to the debug v2 board.

* Connect USB of the debug v2 board to the PC.

* If you have a serial console, start it now. The device should be something like /dev/ttyUSB0.

* Connect the USB cable of the Neo.

* Insert the battery.

* Power on the Neo. (If it has powered on by itself, that's okay.)

* Start OpenOCD (if you have a local openocd.cfg, please use that one):

tmp/openocd -f tmp/openocd-debugv2.cfg

* OpenOCD should print one line (below) and keep running:

Info: openocd.c:84 main(): Open On-Chip Debugger (2007-01-31 12:00 CET)

If OpenOCD prints an error, please disconnect the USB cable of debug v2 from the PC, connect it again, then restart OpenOCD.

* In another window, start the install script:

./devirginate -0 -1 -2

{{note|The '''-0''' option irrecoverably destroys bad block information provided by the chip manufacturer. This is only appropriate for devices from phase 0, or earlier. Instructions will be updated for later models.}}

Watch the screen of the Neo. The following things should happen:
* it turns on, showing weird things for about 10-30 seconds
* the screen goes dark for 1-2 minutes
* the screen lights up and shows a smiling face for a few minutes
* the screen goes dark and shows a partial (broken) OpenMoko logo for about 5-10 seconds
* the screen goes dark again, then shows the full OpenMoko logo
* the machine will boot Linux now and start touch screen calibration

== Errata ==

=== power-off while DFU ===
u-boot can power-off the phone while in DFU mode :(

==== Workaround ====
Either press the AUX button frequently to keep the phone from shutting off while the transfer is in progress, ''or'' access the u-boot console to increase boot_menu_timeout to some large value (in seconds) and restart.

==== Solution ====
Update to a more recent u-boot revision. All builds with svn revision '''1284''' or later address this issue.

=== Licenses not in rootfs image ===
/usr/share/common-licenses is not populated

==== Workaround ====
printed GPL/LGPL included

=== rootfs update causes what seems like bad blocks ===
Since we do block-by-block erasing of the flash during DFU, the 'rootfs' partition is not erased completely before writing a new JFFS2 image to NAND, if the rootfs image is smaller than the flash size

==== Workaround ====
Either use the 'pad' option to '''mkfs.jffs2' when creating the image '''or''' use
GTA01Bv3# nand erase clean rootfs
on the bootloader console before using DFU to flash a new rootfs image

=== Mechanical stress to microSD lid can cause short-circuit ===
If you operate the microSD slot without a card inserted, while the device is powered on, plus put some mechanical stress to it, it can short-circuit the contact pins, resulting in 3.3V supply voltage short-circuit.

==== Workaround ====
Please do not power the phone without microSD card inserted. Especially, never try to switch cards without unpowering the phone completely.

=== Random system crashes ===
Due to a bug in the GPIO initialization routines of our [[u-boot]] patchset up to '''moko5''', we had memory corruption as soon as more than 64MB of SDRAM were used.

==== Workaround ====
None.

==== Solution ====
The real solution is to update to a more recent u-boot revision, such as http://buildhost.openmoko.org/tmp/deploy/images/u-boot-gta01bv3-r3_0_0_1321.bin

=== Rootfs corrupted after flashing via DFU ===
The [[USB DFU]] code for handling the JFFS2 root filesystem partition did not properly erase the rest of the partition, in case you are flashing an image that is smaller than the physical size of the rootfs partition.

==== Workaround ====
Manually issue
nand erase clean rootfs
on the [[u-boot]] commandline before flashing a new rootfs image.

==== Solution ====
Use a u-boot image svn rev. 1306 or higher.

Disassembling Neo 1973

2007-03-12T09:13:13Z

BlueLightning: Grammar correction to previous edit

'''Disassembling the Neo1973'''

{{note|This page was written as of GTA01Bv3 hardware revision and might need updating soon}}

== Back side of Neo1973 ==
[[Image:Gta01b v3 case back white.jpg|700px]]

== Opening back cover ==

To remove the back cover, put your fingernail at the small recession on top of Neo, and pull a bit.

[[Image:Gta01b v3 case back open white.jpg|700px]]

{{note| You now need to remove the two Torx screws (T6x40)}}

== Carefully remove top cover ==
[[Image:Gta01b v3 case side opening white.jpg|700px]]

To remove the top cover, after removing the two torx screws, ''carefully'' squeeze the end of the supplied guitar pick between the cover and the case at the bottom of the device, and then slide the pick up to the top on one side (do not twist the pick). As you slide the pick along, the case retaining clips should come apart with a snapping sound. Repeat the procedure for the other side of the device. To unclip the last remaining large retaining clip at the top, slide the pick all the way to the top (this can be difficult) and then press it in at the centre. By ''careful'' application of force the clip will detach and the cover can then be removed.

== Top case lid removed ==
[[Image:Gta01b v3 case top open white.jpg|700px]]

Visible in this image, from the right, going clockwise.

*The blocky device at the far right is the GPS antenna.
**To the left of this, there are two gold pads, which are where the earpiece speaker connects.
*The [[Debug Board]] connector.
*At the left, the black semicircular device is the GSM antenna.
**Immediately to its right, the small circular black/gold object is the microphone
*At the top right, the ''Aux button''

In the middle is the touchscreen LCD, the touchscreen printed wire can be seen beginning at the bottom left of this, through the glass.

== Lifting the PCB on the left side ==
{{note|You have to bend the plastic case a bit outwards until the headphone jack on the left side of the device becomes loose}}
[[Image:Gta01b v3 case top open pcb lift white.jpg|700px]]

== Removing PCB from case frame ==
{{note|Since the PCB now is loose on one side, you can carefully pull the USB socket and GPS antenna connector out of the right side of the case, and then flip the PCB upwards}}
[[Image:Gta01b v3 case top open pcb lifted.jpg|700px]]

This shows:
*At the top on a green board, the bluetooth module, and the square bluetooth antenna.
*The headset jack is to the right of this.
**Immediately below the headset jack is the [[Neo1973 Battery]] connector.
**Below the [[Neo1973 Battery]] connector, the two gold pads feed the vibrator motor.
*To the right of the headset jack is the left speaker connector.

On the other side of the PCB, going from bottom-right corner down-left.

*The small circular connector is the GSM connector to which an external ariel can be connected with the back removed, or with an alternative back.

*To the left of this is the right speaker connector.
*One of the button switches.
*USB port.
*Micro-SD slot
*SIM slot - overlaying the Micro-SD slot when present.
*Gold GPS antenna connector.
**Immediately above this with the grey wire connection is the connection to the built in GPS antenna.

On the case picture below, you can see the left and right speakers under the translucent plastic, and the vibrator motor in the middle.

== Empty case frame ==

[[Image:Gta01b v3 case empty white.jpg|700px]]

You can actually see the two stereo speakers beneath the translucent cover, and next to it the small vibrator motor.

Next to the top of the picture is a hole near the speaker.
The external GSM antenna connector is accessed through this hole.

== GSM Antenna ==

[[Image:Gta01b v3 gsm antenna.jpg|700px]]

[[Category:Hardware]]

Disassembling Neo 1973

2007-03-12T09:10:37Z

BlueLightning: Add instructions on removing the top cover

'''Disassembling the Neo1973'''

{{note|This page was written as of GTA01Bv3 hardware revision and might need updating soon}}

== Back side of Neo1973 ==
[[Image:Gta01b v3 case back white.jpg|700px]]

== Opening back cover ==

To remove the back cover, put your fingernail at the small recession on top of Neo, and pull a bit.

[[Image:Gta01b v3 case back open white.jpg|700px]]

{{note| You now need to remove the two Torx screws (T6x40)}}

== Carefully remove top cover ==
[[Image:Gta01b v3 case side opening white.jpg|700px]]

To remove the top cover, after removing the two torx screws, ''carefully'' squeeze the end of the supplied guitar pick between the cover and the case at bottom of the device, and then slide the pick up to the top on one side (do not twist the pick). As you slide the pick along, the case retaining clips should come apart with a snapping sound. Repeat the procedure for the other side of the device. To unclip the last remaining large retaining clip at the top, slide the pick all the way to the top (this can be difficult) and then press it in at the centre. By ''careful'' application of force the clip will detach and the cover can then be removed.

== Top case lid removed ==
[[Image:Gta01b v3 case top open white.jpg|700px]]

Visible in this image, from the right, going clockwise.

*The blocky device at the far right is the GPS antenna.
**To the left of this, there are two gold pads, which are where the earpiece speaker connects.
*The [[Debug Board]] connector.
*At the left, the black semicircular device is the GSM antenna.
**Immediately to its right, the small circular black/gold object is the microphone
*At the top right, the ''Aux button''

In the middle is the touchscreen LCD, the touchscreen printed wire can be seen beginning at the bottom left of this, through the glass.

== Lifting the PCB on the left side ==
{{note|You have to bend the plastic case a bit outwards until the headphone jack on the left side of the device becomes loose}}
[[Image:Gta01b v3 case top open pcb lift white.jpg|700px]]

== Removing PCB from case frame ==
{{note|Since the PCB now is loose on one side, you can carefully pull the USB socket and GPS antenna connector out of the right side of the case, and then flip the PCB upwards}}
[[Image:Gta01b v3 case top open pcb lifted.jpg|700px]]

This shows:
*At the top on a green board, the bluetooth module, and the square bluetooth antenna.
*The headset jack is to the right of this.
**Immediately below the headset jack is the [[Neo1973 Battery]] connector.
**Below the [[Neo1973 Battery]] connector, the two gold pads feed the vibrator motor.
*To the right of the headset jack is the left speaker connector.

On the other side of the PCB, going from bottom-right corner down-left.

*The small circular connector is the GSM connector to which an external ariel can be connected with the back removed, or with an alternative back.

*To the left of this is the right speaker connector.
*One of the button switches.
*USB port.
*Micro-SD slot
*SIM slot - overlaying the Micro-SD slot when present.
*Gold GPS antenna connector.
**Immediately above this with the grey wire connection is the connection to the built in GPS antenna.

On the case picture below, you can see the left and right speakers under the translucent plastic, and the vibrator motor in the middle.

== Empty case frame ==

[[Image:Gta01b v3 case empty white.jpg|700px]]

You can actually see the two stereo speakers beneath the translucent cover, and next to it the small vibrator motor.

Next to the top of the picture is a hole near the speaker.
The external GSM antenna connector is accessed through this hole.

== GSM Antenna ==

[[Image:Gta01b v3 gsm antenna.jpg|700px]]

[[Category:Hardware]]