diff --git a/controller_teensy/src/main.cpp b/controller_teensy/src/main.cpp
index bb91f09..0de8403 100644
--- a/controller_teensy/src/main.cpp
+++ b/controller_teensy/src/main.cpp
@@ -81,6 +81,14 @@ uint8_t speedmode=0;
 #define SPEEDMODE_NORMAL 0
 
 
+unsigned long button_start_lastchange=0;
+bool button_start_state=false;
+#define LONG_PRESS_ARMING_TIME 2000
+#define DEBOUNCE_TIME 50
+
+bool armed = false; //cmd output values forced to 0 if false
+
+
 // Global variables for serial communication
 typedef struct{
     uint8_t idx = 0;                        // Index for new data pointer
@@ -122,8 +130,8 @@ SerialFeedback NewFeedbackFront;
 SerialFeedback FeedbackRear;
 SerialFeedback NewFeedbackRear;
 
-#define CURRENT_FILTER_SIZE 100 //latency is about CURRENT_FILTER_SIZE/2*MEASURE_INTERVAL (measure interval is defined by hoverboard controller)
-#define CURRENT_MEANVALUECOUNT 10 //0<= meanvaluecount < CURRENT_FILTER_SIZE/2. how many values will be used from sorted weight array from the center region. abour double this values reading are used
+#define CURRENT_FILTER_SIZE 20 //latency is about CURRENT_FILTER_SIZE/2*MEASURE_INTERVAL (measure interval is defined by hoverboard controller)
+#define CURRENT_MEANVALUECOUNT 4 //0<= meanvaluecount < CURRENT_FILTER_SIZE/2. how many values will be used from sorted weight array from the center region. abour double this values reading are used
 typedef struct{
   int16_t curL_DC[CURRENT_FILTER_SIZE] = {0}; //current will be inverted for this so positive value means consumed current
   int16_t curR_DC[CURRENT_FILTER_SIZE] = {0};
@@ -155,6 +163,8 @@ void checkLog();
 void updateMotorparams( MotorParameter &mp, SerialFeedback &fb);
 void leds();
 
+void readButtons();
+
 void SendSerial(SerialCommand &scom, int16_t uSpeedLeft, int16_t uSpeedRight, HardwareSerial &SerialRef)
 {
   // Create command
@@ -245,7 +255,7 @@ void setup()
 
   pinMode(PIN_THROTTLE, INPUT);
   pinMode(PIN_BRAKE, INPUT);
-  pinMode(PIN_START, INPUT_PULLUP);
+  pinMode(PIN_START, INPUT_PULLUP); //Pressed=High
 
   pinMode(PIN_LED_START, OUTPUT); //Active High
   
@@ -279,6 +289,8 @@ void loop() {
   if (loopmillis - last_adcread > ADCREADPERIOD) { //read teensy adc and filter
     last_adcread=loopmillis;
     readADC();
+
+    readButtons();
   }
 
 
@@ -424,7 +436,7 @@ void failChecks() {
   controllers_connected=controllerFront_connected & controllerRear_connected;
 
   //ADC Range Check
-  if ((throttle_raw >= failsafe_throttle_min) & (throttle_raw <= failsafe_throttle_max)) { //outside safe range. maybe wire got disconnected
+  if ((throttle_raw >= failsafe_throttle_min) & (throttle_raw <= failsafe_throttle_max)) { //inside safe range (to check if wire got disconnected)
     throttle_ok_time=loopmillis;
   }
   if (loopmillis>throttle_ok_time+ADC_OUTOFRANGE_TIME) { //not ok for too long
@@ -445,20 +457,21 @@ void failChecks() {
 
 
 
-  if (!controllers_connected || error_brake_outofrange || error_throttle_outofrange) { //controllers not available
+  if (!controllers_connected || error_brake_outofrange || error_throttle_outofrange) { //any errors?
     throttle_pos=0;
     brake_pos=0;
   }
 }
 
 void sendCMD() {
-  #define BREAK_CMDREDUCE_CONSTANT 500 //cmd gets reduced by an amount proportional to brake position (ignores freewheeling). cmd_new-=BREAK_CMDREDUCE_CONSTANT / second @ full brake. with BREAK_CMDREDUCE_CONSTANT=1000 car would stop with full brake at least after a second (ignoring influence of brake current control/freewheeling)
-  int16_t cmdreduce_constant=map(brake_pos,0,1000,0,(int16_t)(BREAK_CMDREDUCE_CONSTANT*SENDPERIOD/1000)); //reduce cmd value every cycle
-  #define STARTBREAKCURRENT 5 //Ampere. at what point to start apply brake, proportional to brake_pos.
-  #define STARTBREAKCURRENT_OFFSET 0.1 //offset start point for breaking, because of reading fluctuations around 0A
+  #define MINIMUM_CONSTANT_CMD_REDUCE 1 //reduce cmd every loop by this constant amount when freewheeling/braking
+  #define BREAK_CMDREDUCE_PROPORTIONAL 500 //cmd gets reduced by an amount proportional to brake position (ignores freewheeling). cmd_new-=BREAK_CMDREDUCE_PROPORTIONAL / second @ full brake. with BREAK_CMDREDUCE_CONSTANT=1000 car would stop with full brake at least after a second (ignoring influence of brake current control/freewheeling)
+  int16_t cmdreduce_constant=map(brake_pos,0,1000,0,(int16_t)(BREAK_CMDREDUCE_PROPORTIONAL*SENDPERIOD/1000)); //reduce cmd value every cycle
+  #define STARTBREAKCURRENT 5 //Ampere. at what point to start apply brake proportional to brake_pos. for everything above that cmd is reduced by freewheel_break_factor
+  #define STARTBREAKCURRENT_OFFSET 0.1 //offset start point for breaking, because of reading fluctuations around 0A. set this slightly above idle current reading
   float brakepedal_current_multiplier=STARTBREAKCURRENT/1000.0; //how much breaking (in Ampere) for unit of brake_pos (0<=brake_pos<=1000)
 
-  float freewheel_current=STARTBREAKCURRENT_OFFSET+brake_pos*brakepedal_current_multiplier; //above which driving current cmd send will be reduced more. increase value to decrease breaking. values <0 increases breaking above freewheeling
+  float freewheel_current=STARTBREAKCURRENT_OFFSET-brake_pos*brakepedal_current_multiplier; //above which driving current cmd send will be reduced more. increase value to decrease breaking. values <0 increases breaking above freewheeling
   float freewheel_break_factor=500.0; //speed cmd units per amp per second. 1A over freewheel_current decreases cmd speed by this amount (on average)
   motorparamsFront.filtered_curL=filterMedian(motorparamsFront.curL_DC)/50.0; //in Amps
   motorparamsFront.filtered_curR=filterMedian(motorparamsFront.curR_DC)/50.0; //in Amps
@@ -468,19 +481,19 @@ void sendCMD() {
   float filtered_currentFront=max(motorparamsFront.filtered_curL,motorparamsFront.filtered_curR);
   float filtered_currentRear=max(motorparamsRear.filtered_curL,motorparamsRear.filtered_curR);
 
-  filtered_currentAll=max(filtered_currentFront,filtered_currentRear);
+  filtered_currentAll=max(filtered_currentFront,filtered_currentRear); //positive value is current Drawn from battery. negative value is braking current
 
   if (throttle_pos>=last_cmd_send) { //accelerating
     cmd_send = throttle_pos; //if throttle higher than last applied value, apply throttle directly
   }else{ //freewheeling or braking
-    if (filtered_currentAll<freewheel_current) { //drive current too high
-      cmd_send-= max(0, (-filtered_currentAll+freewheel_current)*freewheel_break_factor*(SENDPERIOD/1000.0)); //how much current over freewheel current, multiplied by factor. reduces cmd_send value
+    if (filtered_currentAll>freewheel_current) { //drive current too high
+      cmd_send-= max(0, (filtered_currentAll-freewheel_current)*freewheel_break_factor*(SENDPERIOD/1000.0)); //how much current over freewheel current, multiplied by factor. reduces cmd_send value
     }
-    cmd_send-=max(1,cmdreduce_constant); //reduce slowly anyways
+    cmd_send-=max(MINIMUM_CONSTANT_CMD_REDUCE,cmdreduce_constant); //reduce slowly anyways
     cmd_send=constrain(cmd_send,0,1000);
   }
 
-  if (!controllers_connected) { //controllers not connected
+  if (!controllers_connected || !armed) { //controllers not connected or not armed
     cmd_send=0; //safety off
   }
 
@@ -503,12 +516,12 @@ void sendCMD() {
 
 
 void checkLog() {
-  if (!log_header_written && loopmillis>=WRITE_HEADER_TIME){
-    writeLogHeader(Serial1); //connection recovered, write log header
+  if (!log_header_written && loopmillis>=WRITE_HEADER_TIME){ //write header for log file after logger booted up
+    writeLogHeader(Serial1);
     log_header_written=true;
   }
   
-  if ((log_header_written && log_update && loopmillis>last_log_send+LOGMININTERVAL) || loopmillis>last_log_send+LOGMAXINTERVAL) {
+  if (log_header_written && ( (log_update && loopmillis>last_log_send+LOGMININTERVAL) || loopmillis>last_log_send+LOGMAXINTERVAL) ) {
     last_log_send=loopmillis;
     log_update=false;
     writeLog(Serial1,loopmillis, motorparamsFront,motorparamsRear, FeedbackFront, FeedbackRear, filtered_currentAll, throttle_pos, brake_pos);
@@ -525,7 +538,13 @@ void updateMotorparams( MotorParameter &mp, SerialFeedback &fb) {
 }
 
 void leds() {
-  digitalWrite(PIN_LED_START,(loopmillis/1000)%2 == 0); //high is on for LED_START
+  //Start LED
+  if (!armed) { //disarmed
+    digitalWrite(PIN_LED_START,((loopmillis/1000)%2 == 0)); //high is on for LED_START. blink every second. loopmillis 0 - 1000 led is on.
+  }else{ //armed
+    digitalWrite(PIN_LED_START,HIGH); //LED On
+  }
+  
 
   if (speedmode==SPEEDMODE_SLOW) {
     digitalWrite(PIN_MODE_LEDG,LOW); //Green, low is on
@@ -534,4 +553,30 @@ void leds() {
     digitalWrite(PIN_MODE_LEDG,HIGH);
     digitalWrite(PIN_MODE_LEDR,LOW); //Red
   } 
+}
+
+void readButtons() {
+
+  if (loopmillis > button_start_lastchange+DEBOUNCE_TIME) { //wait some time after last change
+    if (digitalRead(PIN_START) && !button_start_state) { //start engine button pressed and was not pressed before
+      button_start_state=true; //pressed
+      button_start_lastchange=loopmillis; //save time for debouncing
+    }else if (!digitalRead(PIN_START) && button_start_state) { //released an was pressed before
+      button_start_state=false; // not pressed
+      button_start_lastchange=loopmillis; //save time for debouncing
+    }
+  }
+
+  if (button_start_state) { //pressed
+    if ( (loopmillis> button_start_lastchange + LONG_PRESS_ARMING_TIME)) { //pressed long
+      if (throttle_pos<=0 && brake_pos<=0 && !armed) {  //brake or thottle not pressed
+        armed=true; //arm if button pressed long enough
+        writeLogComment(Serial1,loopmillis, "Armed by button");
+      }      
+    }else if (armed){ //not pressed long enough and is armed
+      armed=false; //disarm
+      writeLogComment(Serial1,loopmillis, "Disarmed by button");
+    }
+  }
+
 }
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