--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/doc/Calypso-version-override	Mon Oct 07 03:59:14 2019 +0000
@@ -0,0 +1,39 @@
+TI's TCS211 program supported 3 different Calypso silicon versions on their
+D-Sample and Leonardo boards: C05B (CHIPSET 8, DSP 33), early C035 (CHIPSET 10,
+DSP 34) and final C035 (CHIPSET 10, DSP 36).  In FreeCalypso we generally work
+only with the last chipset (final C035), but we would like to support the two
+earlier ones as well, if possible.  C05B has been partially exercised on the
+Mother's D-Sample board (non-functional Clara RF, no genuine tpudrv10.c source
+and too many unknowns), but the early C035 version with DSP 34 has not been
+tested at all yet.
+
+All 3 Calypso chip versions in question are footprint-compatible, i.e., they
+can all be populated onto the same PCB.  Changing between C05 and C035 requires
+changing the VLRTC strapping on the Iota companion chip, thus not all boards
+can support Calypso C05 (the newer ones are C035 only), but one can always
+populate either early C035 (DSP 34) or final C035 (DSP 36) on the same PCB.
+TI's own D-Sample and Leonardo development boards have most certainly been made
+with all 3 Calypso silicon versions: D-Sample appears to support both C05 and
+C035 on the same PCB; the schematics we have for Leonardo show fixed VLRTC
+strapping for C035, but there also existed an earlier Leonardo version with
+Calypso C05B.  Our own FCDEV3B also has fixed C035-only VLRTC strapping, our
+regular boards have final C035 chips on them, but we should be able to build
+some experimental boards with an early C035 variant (751774) for DSP 34 testing.
+
+In the case of target boards that can have different Calypso chip versions
+populated on them, we want to be able to target all of them without creating a
+configuration explosion.  The implemented solution is that you can pass a target
+argument to the ./configure.sh script of the following form:
+
+dsample-c05b
+dsample-dsp34
+dsample-dsp36
+leonardo-c05b
+leonardo-dsp34
+leonardo-dsp36
+fcdev3b-dsp34
+
+Our configure.sh script recognizes the hyphen as indicating this construct;
+the word before the hyphen must be the conventional target name, and the word
+after the hyphen needs to be one of c05b, dsp34 or dsp36, corresponding to the
+three supported Calypso silicon versions.