--- a/doc/Config-vars	Tue Nov 06 05:03:55 2018 +0000
+++ b/doc/Config-vars	Tue Nov 06 05:20:02 2018 +0000
@@ -55,6 +55,14 @@
 	like in TI's original TCS211 fw.  Note that Melody E1 support is always
 	enabled; setting MELODY_E2=0 disables only Melody E2, but not E1.
 
+RVTMUX_ON_MODEM
+
+	This setting configures the usage of Calypso UARTs.  RVTMUX_ON_MODEM=0
+	puts the AT command interface on the MODEM UART and RVTMUX on the IrDA
+	UART (TI's intended config and the default on sensible hw targets);
+	RVTMUX_ON_MODEM=1 (default on the crippled C1xx targets) puts RVTMUX on
+	the MODEM UART, sacrificing the standard AT command interface.
+
 SERIAL_DYNAMIC_SWITCH
 
 	TI's TCS211 fw includes a provision (only for Bluetooth-enabled fw in
@@ -104,8 +112,8 @@
 
 	The 3 allowed values for this setting are bigcolor, bigbw and 84x48,
 	selecting one of the 3 UI configurations supported by TI's code.  The
-	default is 84x48 when the firmware is built for target c11x or c139,
-	and bigcolor otherwise.
+	default is 84x48 when the firmware is built for target c11x or c139 or
+	c155, and bigcolor otherwise.
 
 USE_STR2IND