Re: My progress with 5V SIM investigation

From: Mychaela Falconia <mychaela.falconia(a)gmail.com> To: simtrace(a)lists.osmocom.org Cc: Bcc: Date: Tue, 25 Oct 2022 20:03:23 -0800 Subject: My progress with 5V SIM investigation Hello SIMtrace community, I mentioned earlier on this list, and also in last week's OsmoDevCall, that I play with some old phones that *may* be putting out 5V toward the SIM, which SIMtrace2 hw does not tolerate - 5V exceeds the absolute maximum rating spec of SAM3S chip. As the first step in the investigation, I cobbled together a simple PCB design for a purely passive adapter that connects a SIM socket to FPC cables from current Sysmocom SIMtrace kits, plus 2.54 mm headers on both sides of the SIM socket providing convenient probing access to all signals. This trivial design can be found in my fc-small-hw Hg repository: https://www.freecalypso.org/hg/fc-small-hw/ Look in the sim-fpc-pasv directory inside the Hg repo. I haven't sent this little PCB out to fab yet, but I plan on doing so when my budget allows it, hopefully no later than a week from now. When I get this adapter board fabbed and assembled, I will test it with my current collection of old phones (Ericsson I888, Nokia 5190 and 6190) and see if any of these phones put out 5V toward the SIM. Nokia 5190 and 6190 are powered by 3-cell NiMH batteries, but they still might put out 5V toward the SIM if they include a charge pump or some other boost converter. At least in TI chipset history, prior to our well-known Calypso+Iota chipset, their previous ABB chip Nausica (used in the legendary TSM30, apparently) could put out either 3V or 5V toward the SIM, selection under fw control, while powered by a 3-cell NiMH or 1-cell Li-ion battery, doing some kind of boost conversion for 5V. (I never found a datasheet for that ancient ABB, so I don't know the full details.) It will be interesting to know what Nokia 5190 and 6190 do in this regard. It will also be interesting to see what Ericsson I888 puts out: it is an older, higher-voltage beast, powered by a 4-cell NiMH battery, and if the designers felt like operating the SIM in "5V" or Class A mode, they could have used raw battery voltage without conversion, as the spec is 4.5 V minimum IIRC. During last week's OsmoDevCall Kevin said that he had some SIMtrace1 boards with ARM7S, which the datasheet says is 5V-tolerant, and I recall him saying that he could send me one. To Kevin: I greatly appreciate your offer, and I may indeed take you up on it in another few weeks - but let me build my sim-fpc-pasv adapter first, and see what voltages are actually put out by phones in my collection. Now the really interesting phone would be Nokia 2190 - supposedly one of the very first PCS1900 band GSM phones sold in USA, from around 1995. That one is powered by a 5-cell NiMH battery and thus seems very likely to put out 5V toward the SIM, possibly always, without ever switching down to 3V. I don't have one to test, aside from a sealed box which I am reluctant to cut open (told it may be worth a fortune some day, the usual story), but another person on Reddit says that these phones are very finicky in terms of which SIMs they accept. I sent him a few of my FCSIM1 cards, equivalent to sysmoSIM-GR2, a pure GSM 11.11 SIM without any UICC at all, very old-fashioned, and my contact tells me that Nokia 2190 rejects these SIMs too! It was my desire to use SIMtrace to see what's happening with that finicky 2190 that prompted my investigation into 5V tolerance - and when I get my sim-fpc-pasv adapter built, I will get back in touch with my Nokia 2190 contact person from Reddit and see how he would like to proceed. M~ _______________________________________________ simtrace mailing list -- simtrace(a)lists.osmocom.org To unsubscribe send an email to simtrace-leave(a)lists.osmocom.org