Hello ladies and gentlemen, A little under a year ago Mr. Sean Moss-Pultz released Openmoko's original PCB design files for GTA02 revisions A1 through A6:
ftp://ftp.freecalypso.org/pub/GSM/GTA02/GTA02_design_files.zip Fast-forwarding to the present, I am now working together with an anonymous company in a non-Western, non-1st-world region, and we are jointly producing a new Calypso modem board that is based on a direct reuse of the modem section from GTA02_MB_A6. The name of the project is FCDEV3B, which stands for FreeCalypso development board, triband. Yes, it is triband like the GTA02 - while I still desire to go to quadband eventually, the change was deemed to be too risky for our first board, hence we are playing it safe and keeping the proven-working GSM RF section completely intact from the GTA02, which necessarily includes keeping the triband RFFE. The board will be 90x50 mm in size, and functionally it will consist of a bare GSM modem with a bunch of interfaces brought out to connectors. A power input connector, an SMA connector for the GSM antenna, headers bringing out both UARTs, JTAG and MCSI at 2.8V logic levels. A SIM socket, PWON and RESET pushbuttons, and analogue loudspeaker and microphone circuits following TI's reference schematics will be on-board. We have made one change to the design which we hope shall fix the infamous bug #1024. Zero-ohm 0402 jumper-resistors at reference designators R1003 and R1004 have been removed, and the power traces have been connected straight through where these 0402 R footprints used to be. TI's reference schematics (unfortunately TI's reference layout appears to have been lost) prescribe star routing for the V-DBB power net, and they have STAR_CONFIG "pseudo-component" symbols in the two branches, but turning these "star points" into physical 0R jumper- resistors must have been FIC/Openmoko's idea. I believe that the latter change contributed to bug #1024; with our change that effectively reverts FIC/Om's change, the layout we have now appears to match TI's intent as expressed on their Leonardo reference schematics, hence I hope that the change we've made will be an improvement. We are also going to populate a 22 uF cap at C214 (Leonardo refdes corresponding to Om's C1009) instead of the originally-called-for 10 uF. The hw rework for bug #1024 on Openmoko-made devices consisted of likewise changing this cap to a higher value, or adding a second 10 uF cap in parallel, hence I hope that even if the bug does not get fixed with our layout change, it will nonetheless be nipped in the bud by our use of a larger capacitor. But please feel free to look at our design files and judge for yourselves: ftp://ftp.freecalypso.org/pub/GSM/FreeCalypso/fcdev3b/ The latest revision as of right now is the one with 20160220 in the filenames. It still has a few outstanding issues which we are going to fix, so it isn't 100% final yet, but the day when we declare our design to be finished and send it out to PCB fab is approaching very soon, hence I decided to give this list an opportunity to review our work, particularly my thoughts regarding bug #1024 and my approach to fixing it, before it is too late. M~ P.S. When we get this board built and working, we are going to offer them for sale to anyone who wants one on a retail basis, but we also freely publish all of our design files, hence anyone else is free to run their own production based on our design. _______________________________________________ hardware mailing list [email protected] http://lists.openmoko.org/mailman/listinfo/hardware
