USB startup: Ensure that we are not talking to the peripheral too soon. Startup does not take longer due to smart rearrangement of launch calls

ROMFS/px4fmu_common/init.d/rcS

@@ -5,6 +5,11 @@
 #  NOTE: COMMENT LINES ARE REMOVED BEFORE STORED IN ROMFS.
 #
 
+#
+# Start CDC/ACM serial driver
+#
+sercon
+
 #
 # Default to auto-start mode.
 #
@@ -43,29 +48,8 @@ else
 fi
 unset FRC
 
-# if this is an APM build then there will be a rc.APM script
-# from an EXTERNAL_SCRIPTS build option
-if [ -f /etc/init.d/rc.APM ]
-then
-	if sercon
-	then
-		echo "[i] USB interface connected"
-	fi
-
-	echo "[i] Running rc.APM"
-	# if APM startup is successful then nsh will exit
-	sh /etc/init.d/rc.APM
-fi
-
 if [ $MODE == autostart ]
 then
-	echo "[i] AUTOSTART mode"
-
-	#
-	# Start CDC/ACM serial driver
-	#
-	sercon
-
 	# Try to get an USB console
 	nshterm /dev/ttyACM0 &
 

src/systemcmds/nshterm/module.mk

@@ -38,7 +38,7 @@
 MODULE_COMMAND	 = nshterm
 SRCS		 = nshterm.c
 
-MODULE_STACKSIZE = 1600
+MODULE_STACKSIZE = 1500
 
 MAXOPTIMIZATION	 = -Os
 

src/systemcmds/nshterm/nshterm.c

@@ -50,6 +50,7 @@
 #include <apps/nsh.h>
 #include <fcntl.h>
 #include <systemlib/err.h>
+#include <drivers/drv_hrt.h>
 
 #include <uORB/topics/actuator_armed.h>
 
@@ -67,6 +68,11 @@ nshterm_main(int argc, char *argv[])
     int armed_fd = orb_subscribe(ORB_ID(actuator_armed));
     struct actuator_armed_s armed;
 
+    /* back off 800 ms to avoid running into the USB setup timing */
+    while (hrt_absolute_time() < 800U * 1000U) {
+        usleep(50000);
+    }
+
     /* try to bring up the console - stop doing so if the system gets armed */
     while (true) {