diff --git a/ecmc_plugin_grbl/ecmcGrbl.cpp b/ecmc_plugin_grbl/ecmcGrbl.cpp
index 35f3e49..c651e55 100644
--- a/ecmc_plugin_grbl/ecmcGrbl.cpp
+++ b/ecmc_plugin_grbl/ecmcGrbl.cpp
@@ -383,10 +383,10 @@ void  ecmcGrbl::grblRTexecute() {
   
   autoEnableAtStart();
 
-  double sampleRateMs =.0;
+  double sampleRateMs =0.0;
 
   if(grblInitDone_ && autoEnableExecuted_) {
-    while(timeToNextExeMs_ < exeSampleTimeMs_) {
+    while(timeToNextExeMs_ < exeSampleTimeMs_ && sampleRateMs >= 0) {
       sampleRateMs=ecmc_grbl_main_rt_thread();
       timeToNextExeMs_ = timeToNextExeMs_ + sampleRateMs;
     }
diff --git a/grbl/grbl_stepper.c b/grbl/grbl_stepper.c
index d88c456..d7ddf7c 100644
--- a/grbl/grbl_stepper.c
+++ b/grbl/grbl_stepper.c
@@ -373,7 +373,7 @@ double ecmc_grbl_main_rt_thread()
 { 
   //printf("%s:%s:%d\n",__FILE__,__FUNCTION__,__LINE__);
 
-  if (busy || !stepperInterruptEnable) { return 0.0; } // The busy-flag is used to avoid reentering this interrupt
+  if (busy || !stepperInterruptEnable) { return -1.0; } // The busy-flag is used to avoid reentering this interrupt
 
   // Set the direction pins a couple of nanoseconds before we step the steppers
   //DIRECTION_PORT = (DIRECTION_PORT & ~DIRECTION_MASK) | (st.dir_outbits & DIRECTION_MASK);
@@ -464,7 +464,7 @@ double ecmc_grbl_main_rt_thread()
         if (st.exec_block->is_pwm_rate_adjusted) { spindle_set_speed(SPINDLE_PWM_OFF_VALUE); }
       #endif
       system_set_exec_state_flag(EXEC_CYCLE_STOP); // Flag main program for cycle end
-      return 0.0; // Nothing to do but exit.
+      return -1.0; // Nothing to do but exit.
     }
   }
 
@@ -541,7 +541,7 @@ double ecmc_grbl_main_rt_thread()
   busy = false;
 
   if(!st.exec_segment) {
-    return 0.0;
+    return -1.0;
   }
   return st.exec_segment->ecmc_interrupt_time_ms;
 }
diff --git a/iocsh/test.script b/iocsh/test.script
index 748bbe3..f3ad6e2 100644
--- a/iocsh/test.script
+++ b/iocsh/test.script
@@ -63,16 +63,16 @@ ${SCRIPTEXEC} ${ecmccfg_DIR}loadPlugin.cmd, "PLUGIN_ID=0,FILE=${ECMC_PLUGIN_FILN
 epicsEnvUnset(ECMC_PLUGIN_FILNAME)
 epicsEnvUnset(ECMC_PLUGIN_CONFIG)
 
-ecmcGrblAddCommand("G1X20Y20F300");
+ecmcGrblAddCommand("G1X20Y20F180");
 ecmcGrblAddCommand("G4P1");
 ecmcGrblAddCommand("G2X0Y0R20");
 ecmcGrblAddCommand("G0X10Y10");
 ecmcGrblAddCommand("G4P1");
-ecmcGrblAddCommand("G1X10Y0F200");
+ecmcGrblAddCommand("G1X10Y0F360");
 ecmcGrblAddCommand("G4P1");
-ecmcGrblAddCommand("G1X50Y50F300");
+ecmcGrblAddCommand("G1X50Y50F180");
 ecmcGrblAddCommand("G4P1");
-ecmcGrblAddCommand("G1X0Y0F180");
+ecmcGrblAddCommand("G1X0Y0F360");
 #
 #ecmcGrblAddCommand("$");
 #