Hello FreeCalypso community, After running a few more tests I reached the conclusion that the most likely reason why our FCDEV3B running FC Magnetite fw is currently unable to connect to a live commercial GSM network is not because of some physical problem with the RF tract, but simply because of the lack of calibration for the VCXO. I have reached this conclusion based on the following observations:
1. Serg and Harald asked me to try running OsmocomBB on this board. I did as they asked (when running OsmocomBB on the FCDEV3B, use the gta0x version of layer1.highram.bin, *not* any of the compal ones - the gta0x build works unchanged on the FCDEV3B), and it appears to work. I did not take it as far as running the full mobile app (I may try it next), but I ran their cell_log app, and it found the local cells of Operator 310260, and reported the TA for each of them. Finding the TA requires sending a RACH and getting an IMM ASS back, thus having cell_log work to this extent indicates that the RF tract on the FCDEV3B must be good in both Rx and Tx directions! 2. As an experiment, I fully erased the FFS on a GTA02 modem, reinitialized it with just /etc/IMEISV and /gsm/com/rfcap (no RF calibration files), and tried connecting to the network. Result: it fails in exactly the same way as our FCDEV3B currently does. When I restored the afcdac and afcparams files under /gsm/rf and rebooted, the modem happily connected to my local cell - thus it is the VCXO calibration that's critical here, not any other Rx or Tx calibration parameters. Now here are the two big questions to which I have no answers: 1. The AFC algorithm used by OsmocomBB looks totally different from the one used by TI's TCS211 fw, and I am not enough of a guru to understand the differences between the two or their relative merits. OsmocomBB's version does not require calibration and has no provision for making use of such, whereas TI's version expects that each MS gets individually calibrated on the production line. Doing per-unit calibration on production lines requires time and special equipment, i.e., money. I figure that the mainstream manufacturers would not be doing such per-unit calibration if it could be avoided, hence there must be some good reason for doing this calibration. But if so, then how is OsmocomBB able to get away with having no calibration provisions at all? 2. When we run our FreeCalypso firmwares on Mot C1xx phones, we don't have any calibration values (Compal did not use TI's standard format, and we don't know how to grok their proprietary one), yet our firmwares running on these targets connect to GSM networks just fine. But the very same sans-calibration configuration with the same fw fails on GTA02 and FCDEV3B hardware! Just to be clear, the purpose of the FCDEV3B is to run TCS211 or TCS2/TCS3 hybrid firmware in its full glory. Running OsmocomBB on the FCDEV3B is certainly possible, but pointless: right this moment there are 29 listings on ebay for Mot C139 phones, with prices in the $5 to $20 range, and for OsmocomBB our FCDEV3B offers absolutely no advantage over these obscenely cheap Mot C1xx phones, hence buying a very expensive board like ours only to run OsmocomBB would be a waste of money. Instead the purpose of our board is run TI's TCS211 fw in its full glory with CSD, fax and GPRS services, which is not possible on Mot C1xx phones. Hence in order to achieve our goal of running the firmware we like, it looks like we will have to bite the bullet and calibrate our boards on the CMU200 before we'll able to connect to GSM networks using our choice of fw. Climbing the very steep learning curve of the CMU200 and of the calibration procedures is now on my to-do list. Hasta la Victoria, Siempre, Mychaela aka The Mother _______________________________________________ Community mailing list Community@freecalypso.org https://www.freecalypso.org/mailman/listinfo/community