EFM32 Gecko Starter Kit: Calibrate delay loops, update README

configs/efm32-g8xx-stk/README.txt

@@ -35,7 +35,26 @@ STATUS
     appears to be sent (at least by efm32_lowputc()).  However, no signal
     activity is present on PE0.
 
-  I am, of course, thinking that this is a pin configuration issue.
+  2014-10-29:  The NuttX is running on the EFM32 Gecko Starter Kit.  There
+    are not many peripherals to test in that configuration, but the NuttShell
+    (NSH) is working over LEUART0 at 2400 baud (certainly that could go up
+    to 4800.  The documentation says that 9600 is also possible on the
+    LEUART, but I am not sure how).
+
+    I originally planned to use UART0 at 115200 baud, but I never could get
+    any output from the board.  I reviewd my pin configuration and clocking
+    carefully and the USART seems to think it is working correctly.  So I
+    am thinking that there is some board issue that prohibits that option
+    (probably because UART0 is used with the board controller???).  Pins
+    are not available for other U[S]ARTs on the board.
+
+  2014-10-29:  Calibrated the delays loops.
+
+  2014-10-29:  The start-up time is long -- about a second.  I have traced
+    this to the default delay in bringing up the LFCLK in efm32_clockconfig.
+    The default, reset setting of the LFXOTIMEOUT field of the CMU_CTRL
+    register is 3 which corresponds to a delay of 32768 cycles, or a full
+    second.  I have not experimented to see if this delay can be reduced.
 
 LEDs
 ====

configs/efm32-g8xx-stk/nsh/defconfig

@@ -192,7 +192,7 @@ CONFIG_ARCH_HAVE_RAMVECTORS=y
 #
 # Board Settings
 #
-CONFIG_BOARD_LOOPSPERMSEC=4531
+CONFIG_BOARD_LOOPSPERMSEC=2662
 # CONFIG_ARCH_CALIBRATION is not set
 
 #

configs/olimex-efm32g880f128-stk/nsh/defconfig

@@ -189,7 +189,7 @@ CONFIG_ARCH_HAVE_RAMVECTORS=y
 #
 # Board Settings
 #
-CONFIG_BOARD_LOOPSPERMSEC=4531
+CONFIG_BOARD_LOOPSPERMSEC=2662
 # CONFIG_ARCH_CALIBRATION is not set
 
 #