Reported by Nikolaus Schaller, Dec 7, 2013
To fulfill the FSF "freedom" requirement: "* The microphone and the GPS should be connected to the main computer, not to the radio modem." 1. built into UMTS/LTE module (does not fulfill requirement but is the cheapest) 2. W2SG0084 3. uBlox EVA 7m http://www.u-blox.com/de/press-and-events/press-release-archive/1556- u-blox-launches-eva-7m-industrys-smallest-standalone-gnss-module.html The idea is not really to choose between them but allow any option. I.e. have the fottprint of all and maybe just solder a different 0R to connect the LNA output to either one. Maybe 2/3 are alternative (because they also have to share an UART). Problem is that 2.&3. may be expensive (2. is ca. 15 EUR in BOM, 3. may be 50 EUR) while 1. comes for free.
Comment 1 by Joerg Reisenweber, Dec 7, 2013
FSF evidently has no ideas about hw alternatives, so their "requirements" are just the "standard" way to go. Thinking about the rationale behind the GPS requirements you find that same purpose can get accomplished by reliably disabling the GPS antenna. Easy to implement, no RF routing nightmare with 0R (DNP) "jumpers" and no wasting of PCB real estate for footprints of chips (DNP). btw FSF has more "requirements" for hw, some of them totally insane. I don't plan to comply with Mr Stallman's ideas, rather carry on the spirit and do better. According to USB authorities we mustn't offer hostmode, according to FSF we mustn't use WLAN with firmware blob etc pp. I need no help to define a free and useful good hw design.
Comment 2 by Nikolaus Schaller, Dec 7, 2013
There are good reasons to think about having a separate GPS receiver (independently of FSF's argumentations): * we can offer GPS on a device that has no modem at all (PDA style) * we can get a highly precise Pulse Per Second interrupt from a separate receiver * we can be sure that the UMTS modem can't control or read out the GPS receiver (this is what FSF wants to protect us against, not from using GPS at all) * the u-blox can provide 10 position updates per second * it may (has to be checked) need less power Therefore my proposal to think about it and if we have the space on the Lower board we can add the footprints. And people can either get the cheapest variant or pay more for one of the benefits described above.
Comment 3 by Joerg Reisenweber, Dec 7, 2013
we can test it on one of the protos, see what it gives us: options or flaws. Footprints are cheap, cost real estate only
Comment 4 by ben deering, Mar 25, 2014
I often think of my GTA04 as a GPS that can make telephone calls. If neo900 has no internal GPS that is isolated from the UTMS chip that would be a dissapointment and would appear to run contrary to the design goals of neo900 + untrusted UTMS chip; the UTMS chip would have access to location data any time the user wanted location data. A GPS that can be trusted not to broadcast position seems like one of the best uses of the limited real-estate in the neo900 board, or possibly a daughter board that would let users move the antenna coax from a UFL connector connected to the UTMS internal GPS to the (optional?) daugherboard. I don't know enough about the space created by the spacer ring, or about RF circuit design to know if a daugherboard is feasible at all.
Comment 5 by Joerg Reisenweber, Mar 25, 2014
thanks to tight monitoring of the modem you can still trust in it not sending anything to the air, even when you activate it for GPS usage. Of course you couldn't stop it fast enough when it ever would decide to actually send something despite you instructed it not to do, but then OTOH this is still better than a GPS you don't know if it has a transmitter built in and nobody told us about it. At least you'd know the very second it tries to cheat on you and you could decide what to do about it. If that's still too high a risk, you better choose a GPS device that can't "make telephone calls"
Comment 6 by Joerg Reisenweber, Mar 25, 2014
ps: nota bene that using WWAN and still hoping to hide your position from network while user _can_ readout the position from an isolated GPS chip is a useless dream since WWAN gives away your position even without any GPS, when active. Just a bit more effort needed by carrier to find out about your position, and precision might be in the 20..50m range instead of 2..5m with GPS
Comment 7 by ben deering, Mar 26, 2014
I don't want to clutter the issues discussion page, but I think there is value in separating these functions. Where I live there is often only 1 visible tower and where I play there is often none so base-station location tracking gets me within ~10km. The modem would also have the possibility of logging location history when no basestation is available for hours/days. Several products now contain GPS-related 'anti-features' such as not allowing geotagging while in China, imposing a maximum speed on sports-cars unless the GPS indicates they are at a race-track, etc. The neo900 discussions on the forum and the mailing list have had to answer the 'open device with a closed modem' question dozens of times. I am satisfied with the answer 'modem will only have access to what it needs, can be turned off, and can be monitored', but GPS location is not something the modem needs.
Comment 8 by Joerg Reisenweber, Mar 26, 2014
We'll see what initial tests will yield. See Nikolaus' first post that states a 100EUR for BOM, if we go for a separate GPS which really is worth it. Development and testing costs (prototypes, field tests, PV) go on top of that, so depending on how many would want to buy this option, we have to increase the price by *significantly* >100EUR per device for that option. When you think a 100 users would be willing to pay 200EUR on top (ballpark figures) then it's no problem.
Comment 9 by Joerg Reisenweber, Mar 26, 2014
OOPS, sorry. Usual doble-normalization-mistake. BOM: 50EUR, sales price 100EUR (though the rule of thumb usually is "3 times the chip cost is sales price"). However the needed prototypes particularly for that separate GPS chip solution and the development and testing work still is the same, and we can't make all devices more expensive to finance those expenses for a few users who want the very special option to use GPS while WWAN active and yet WWAN doesn't know about GPS position. The logging inside WWAN would be theoretically possible *only as long as user enables GPS (otherwise it's blocked by shorting the antenna)* but that would mean the modem firmware would need a malware function supporting this, since readout of such log isn't a part of standard GSM specs. Such malware function would be useful for Neo900 only since for all other devices using the Cinterion modem there are way simpler methods of acquiring same data realtime and without firmware patch. I honestly wonder if a GPS module attached to the expansion slot wouldn't be a better option for those interested in such "modem-less" GPS
Comment 10 by Kuper, Mar 27, 2014
If it is true that a primary reason for considering buying a Neo900 is that it does not compromise any more than absolutely necessary w.r.t. privacy and freedom, then surely the default option should be to have the microphone and the GPS connected to the main computer, not to the radio modem. I suppose you could offer a compromised phone at a lower price, but the more compromises, the more you'd be putting it in direct competition with the Replicant-compatible mainstream devices, the Fairphone, etc.
Comment 11 by Joerg Reisenweber, Mar 27, 2014
please don't abuse this as forum! there's http://talk.maemo.org/showthread.php?t=91142 for that Thanks!
Comment 12 by ben deering, Apr 15, 2014
http://www.digikey.com/product-search/en?K=943-1019-1-ND;site=us;lang =en&WT.z_lt=943-1019-1-ND&WT.z_supplier_id=943&WT.z_ref_p age_id=14&WT.z_tz_page_sec=Modules&WT.z_TechZone_Name=Wireles s Jupiter SE880 is in 4.7 x 4.7 x 1.4 mm, 34 pins LGA package Very small, a little power hungry, capable of 5hz updates.
Comment 13 by ben deering, Jul 7, 2014
Note: I was wrong about this device being power hungry. The ma looked high compared to others, but it was because the operating voltage is lower.