diff FCDEV3B-repackaging @ 6:700d6cff63bb

FCDEV3B-repackaging: new ideas regarding quadband RFFE TSPACT wiring
author Mychaela Falconia <falcon@freecalypso.org>
date Thu, 11 Oct 2018 05:44:22 +0000
parents f920c9a68d45
children f57f29dcc6d6
line wrap: on
line diff
--- a/FCDEV3B-repackaging	Thu Oct 11 04:58:17 2018 +0000
+++ b/FCDEV3B-repackaging	Thu Oct 11 05:44:22 2018 +0000
@@ -251,10 +251,41 @@
 
 If anyone ever does pay for the creation of a quadband version of our
 FreeCalypso modem solution, be it in BenQ's physical form factor or some other,
-this quadband modem will need a different firmware build configuration: there
-is no way to have the same fw image work on both triband and quadband modems
-given that the RFFE control signals are different, and there would be no way for
-the fw to autodetect which hw it is running on.  But all of the other design
-guidelines listed above should still be followed, so we can have only two fw
-build configurations (triband and quadband) without an explosion of further
-build variants for different GPIO wiring and whatnot.
+what about the firmware?  For a long time I thought that a quadband modem would
+need a different firmware build configuration because of incompatible TSPACT
+signals.  Our current triband modem (copied from Openmoko) has them wired like
+this:
+
+TSPACT2 = Tx high bands
+TSPACT1 = Rx PCS band
+TSPACT4 = Tx low bands
+
+But TI's original TSPACT wiring for the quadband RFFE on their Leonardo and
+E-Sample boards was different:
+
+TSPACT2 = Tx low bands
+TSPACT1 = Tx high bands
+TSPACT4 = Rx GSM850 band
+
+These two TSPACT signal assignments are mutually incompatible, hence if we make
+a quadband modem following TI's original Leonardo/E-Sample TSPACT wiring, it
+won't be able to share the same fw with our triband modems.  But then I got an
+idea: what if we wire them up in our own creative way as follows:
+
+TSPACT2 = Tx high bands
+TSPACT4 = Tx low bands
+TSPACT5 = Rx GSM850 band
+
+Then we can have the same fw build configuration support both triband and
+quadband FreeCalypso modems by driving the signals as follows:
+
+TSPACT1 = Rx PCS band
+TSPACT2 = Tx high bands
+TSPACT4 = Tx low bands
+TSPACT5 = Rx GSM850 band
+
+TSPACT1 will be driven but unused on quadband modems, whereas TSPACT5 will be
+driven but unused on triband ones like our current FCDEV3B.  To me (Mother
+Mychaela) being able to have the same fw among *all* FreeCalypso modem variants,
+both triband and quadband, is more valuable than the symbolic act of recreating
+TI's original RFFE wiring, hence I am now leaning toward this new approach.