text: <user>
  Create a function block for a Phidget analog sensor interface in TwinCAT Structured Text<|endoftext|>
  <assistant>
  FUNCTION_BLOCK FB_PhidgetAnalogSensor
  VAR_INPUT
      bEnable         : BOOL;     // Enable sensor reading
      nSensorChannel  : USINT;    // Sensor channel (1-4)
  END_VAR
  
  VAR_OUTPUT
      fSensorValue    : REAL;     // Sensor reading (0-5V)
      bError          : BOOL;     // Error flag
      sErrorMsg       : STRING;   // Error message
  END_VAR
  
  VAR
      fbADSRead       : ADSREAD;  // ADS read function block
      nADSState       : UINT;     // ADS read state
      nRawValue       : UINT;     // Raw sensor value
  END_VAR
  
  // Main program
  IF bEnable THEN
      // Configure ADS read
      fbADSRead(
          NETID   := '', 
          PORT    := 851,
          IDXGRP  := 16#4020,
          IDXOFFS := 16#0000 + (nSensorChannel - 1) * 2,
          LEN     := 2,
          DESTADDR:= ADR(nRawValue)
      );
      
      // Execute ADS read
      fbADSRead(READ := TRUE);
      nADSState := fbADSRead.ERR;
      
      // Process result
      IF nADSState = 0 THEN
          // Convert raw value to voltage (0-5V)
          fSensorValue := INT_TO_REAL(nRawValue) * 5.0 / 32767.0;
          bError := FALSE;
          sErrorMsg := '';
      ELSE
          bError := TRUE;
          sErrorMsg := CONCAT('ADS Read Error: ', UINT_TO_STRING(nADSState));
      END_IF
  ELSE
      fSensorValue := 0.0;
      bError := FALSE;
      sErrorMsg := '';
  END_IF
  
  (* 
  This function block provides an interface for reading Phidget analog sensors in TwinCAT 3.
  It uses ADS communication to read the sensor value and converts it to a 0-5V range.
  
  Key features:
  1. Configurable sensor channel (1-4)
  2. Error handling for ADS communication
  3. Automatic conversion of raw value to voltage
  
  Related TwinCAT 3 features that could enhance this implementation:
  1. EtherCAT: Use EtherCAT terminals for more precise and faster analog readings
  2. Scope View: Implement data logging to visualize sensor readings over time
  3. TwinCAT HMI: Create a user interface for sensor monitoring and configuration
  *)<|endoftext|>
  