  // holdingRegs[ADC_VAL] = analogRead(A0);
   
  digitalWrite(LED, HIGH);
- delay(holdingRegs[PWM_VAL]);
+ delay(holdingRegs[reg0_VAL]);
  digitalWrite(LED, LOW);
- delay(holdingRegs[PWM_VAL]);
+ delay(holdingRegs[reg1_VAL]);
  
 }

//////////////// registers of your slave ///////////////////
enum 
{
  ADC_VAL,     
  PWM_VAL,        
  HOLDING_REGS_SIZE
};


void setup()
{
  modbus_configure(&Serial, 19200, SERIAL_8N1, 1, 2, HOLDING_REGS_SIZE, holdingRegs);
  modbus_update_comms(19200, SERIAL_8N1, 229);
  
  pinMode(LED, OUTPUT);
}
