S_ADCToVoltageOrCurrent (FB)

Epec Programming and Libraries Manual

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Supported platforms: CODESYS 3.5, CODESYS 3.5 SAFETY

S_ADCToVoltageOrCurrent (FB)

Description

This function block is used to convert control unit AD converter value to current (µA) or voltage (mV). The function block can be used when analog sensors (0-5V, 0-10V or 0-22mA) are connected to control unit’s AI pin. Cat. 2 type AI pin is also supported.

Initialization

Init method is used to initialize the necessary static calculation parameters for the function block instance.

The method shall be called at least once before the actual function block can be called, i.e. at the application initialization phase.

The method checks the validity of input parameters. However, none of the function block outputs are affected by the initialization.

A parameter error is diagnosed if:

Init method is not called before the main FB call OR
i_pEventCode = 0 OR
S_i_OutputMaximum <= 0 OR
S_i_OutputHighLimit > S_i_OutputMaximum OR
S_i_OutputLowLimit >= S_i_OutputHighLimit OR
S_i_OutputLowLimit < 0

S_i_Cat2MonitoringCh is set to TRUE only to current input pin's redundant-channel.

Initialization parameters

Parameter	Type	Unit	Range	Description
S_i_OutputMaximum	ENUM	mV /µA	EPEC_HW. VALUE_AT_ AD_MAXIMUM	mV/µA value at AD maximum
S_i_OutputHighLimit	SAFEDINT	mV / µA	>0	Limit value for status o_Status.OutputTooHigh
S_i_OutputLowLimit	SAFEDINT	mV /µA	>=0	Limit value for status o_Status.OutputTooLow
S_i_DiagnosticDelay	SAFEUINT	ms	-	Delay time for output high/low diagnostics
S_i_Cat2MonitoringCh	SAFEBOOL	-	-	Is this channel a CAT2 monitoring channel.
i_pEventCode	POINTER TO EventCode	-	≠0	Pointer to application variable which is type EventCode.

Initialization method return value

TRUE: All initialization parameters ok.

FALSE: Error in initialization parameter(s).

Operation

When i_Enable is TRUE, the function block converts the input ADC value (i_ADCValue) to voltage (mV) or current (µA) value.

The input pin type can be either voltage or current.

If Cat. 2 monitoring channel is not in use the equation 3 can be used to calculate output value.

S_o_Output minimum is however limited to 0.

If Cat. 2 monitoring channel is in use then output current can be calculated with equation 4

, where G_CAT2_OUTPUT_MAX is theoretical maximum current.

If the calculated output value is lower than S_i_OutputLowLimit or higher than S_i_OutputHighLimit for longer (≥) than given diagnostic delay time, the corresponding error output is set.

A parameter error is diagnosed if AD input value exceeds defined maximum value G_ADC_MAXIMUM_VALUE.

The output S_o_Output is set to safe value (0) if any error occurs, also o_Status.OutputValid is set false and the corresponding event ID is set to EventCode.

Limitations

Cat. 2 monitoring channel can be used only with current input pin.

Inputs

Input variable name	Data type	Range	Description
i_Enable	BOOL	TRUE / FALSE	Enable calculation
i_ADCValue	DWORD	0 - G_ADC_MAXIMUM_VALUE	AD converter value to be scaled

Outputs

Output variable name	Data type	Unit	Range	Description
S_o_Output	SAFEDINT	mV / µA	-	Calculated voltage or current value
o_Status	Status	-	-	Status of output value. See Status structure.

Error diagnostic

See Diagnostic Interface library description of error status and event code functionality.

Conditions	S_o_Output value	o_Status. OutputValid	o_Status error status	Event code FunctionID	Event code EventID
i_Enable TRUE AND init parameter error AND i_pEventCode valid	0	FALSE	ParameterError	ADC_TO_VOLTAGE OR_CURRENT	PARAMETER_ERROR
i_Enable TRUE AND init parameter error AND i_pEventCode NULL	0	FALSE	ParameterError	-	-
i_Enable rises AND init parameters ok AND S_i_OutputLowLimit <= S_o_Output <= S_i_OutputHighLimit	calculated value	TRUE	-	NO_FUNC	NO_ERROR
i_Enable TRUE AND parameters ok AND S_o_Output > S_i_OutputHighLimit	0	FALSE	OutputHigh	ADC_TO_VOLTAGE OR_CURRENT	OUTPUT_TOO_HIGH
i_Enable TRUE AND parameters ok AND S_o_Output < S_i_OutputLowLimit	0	FALSE	OutputLow	ADC_TO_VOLTAGE OR_CURRENT	OUTPUT_TOO_LOW

Example code

MultiTool Creator generated code includes this function block, when the input is selected to use.

Location of the POU instance depends on the application: Non-safe inputs are handled in non-safe context, safe inputs are handled in safe context. The example code applies to both.

Definitions:

(*NOTE! This object is created by Epec MultiTool Creator*)

VAR_INPUT

i_Enable: BOOL := TRUE;

i_AI_XM1_3:DWORD; // Input AD value

END_VAR

VAR_OUTPUT

S_o_AI_XM1_3: SAFEDINT; // Non-validated voltage value (mV)

o_XM1_3_Status_ToVoltage: EPEC_SC.Status; // Conversion status

o_XM1_3_EventCode: EPEC_DITF.EventCode; // Event code of the input

END_VAR

VAR

S_1_03_ToVoltage: EPEC_SC.S_ADCToVoltageOrCurrent;

init_ok: BOOL := FALSE;

END_VAR

Initialization:

(*NOTE! This object is created by Epec MultiTool Creator*)

o_XM1_3_EventCode.DeviceID := DeviceIDs.VoltageInput;

o_XM1_3_EventCode.ChannelID := ChannelIDs.Ch1;

o_XM1_3_EventCode.FunctionID := EPEC_DITF.FunctionIDs.NO_FUNC; // No function has detected an error

o_XM1_3_EventCode.EventID := EPEC_DITF.ErrorIDs.NO_ERROR; // No error occurred by default

init_ok := S_1_03_ToVoltage.Init(

S_i_OutputMaximum := EPEC_HW.VALUE_AT_AD_MAXIMUM.U_TYPE096_5V, // 5V input

S_i_OutputHighLimit := EPEC_HW.Constants.G_AI_5V_HIGH_VOLTAGE, // High limit of voltage value

S_i_OutputLowLimit := EPEC_HW.Constants.G_AI_LOW_VOLTAGE, // Low limit of voltage value

S_i_Cat2MonitoringCh:= FALSE, // Input is not a CAT2 monitoring channel

S_i_DiagnosticDelay := EPEC_HW.Constants.G_VOLTAGE_INPUT_DIAGNOSTIC_DELAY, // Delay for error diagnostic

i_pEventCode := ADR(o_EC_XM1_3) // Event code pointer for FB

);

Code:

(*NOTE! This object is created by Epec MultiTool Creator*)

S_1_03_ToVoltage(

i_Enable := i_Enable,

i_ADCValue := i_AI_XM1_3,

o_Status => o_XM1_3_Status_ToVoltage,

S_o_Output => S_o_AI_XM1_3

);