# TwoPoint

## `TwoPoint` (FB)

FUNCTION\_BLOCK TwoPoint

### Short description

> Linear conversion of a numerical input value using a characteristic curve defined by two points.

### Representation

<figure><img src="/files/0cbb7f7b8caa9ba142075a9c56641dfc9c2c0a8b" alt=""><figcaption></figcaption></figure>

### Interfaces

#### Inputs

| Name     | Data type | Value range | Initial value | Function           |
| -------- | --------- | ----------- | ------------- | ------------------ |
| *rIn\_X* | REAL      |             | 0             | Analog value input |

#### Outputs

| Name      | Data type | Value range | Initial value | Function                                                                                                                       |
| --------- | --------- | ----------- | ------------- | ------------------------------------------------------------------------------------------------------------------------------ |
| *rOut\_Y* | REAL      |             |               | Analog value output                                                                                                            |
| *xErr*    | BOOL      |             |               | <p>\* <strong>FALSE:</strong><br>Conversion error-free<br>\* <strong>TRUE:</strong><br>Error during the conversion process</p> |

#### Setpoints / parameters

| Name              | Data type | Value range | Initial value | Function                                                        |
| ----------------- | --------- | ----------- | ------------- | --------------------------------------------------------------- |
| **iMinMaxOffset** | INTEGER   |             | 0             | Values of the limits at the analog value output *rOut\_Y*       |
| **xMinMaxLimit**  | BOOL      |             | FALSE         | Enable / disable the limit at the analog value output *rOut\_Y* |
| **rY2**           | REAL      |             | 100           | Point 2 of the output characteristic curve                      |
| **rX2**           | REAL      |             | 100           | Point 2 of the input range                                      |
| **rY1**           | REAL      |             | 0             | Point 1 of the output characteristic curve                      |
| **rX1**           | REAL      |             | 0             | Point 1 of the input range                                      |

### Function description

#### Analog value output *rOut\_Y*

The analog value output *rOut\_Y* is determined by the analog value input *rIn\_X* depending on the linear characteristic curve defined by the two points P1(**rX1**/**rY1**) and P2(**rX2**/**rY2**) is calculated.\
In the event of a conversion error ( *xErr* = TRUE ) the analog value output *rOut\_Y* remains unchanged.

<figure><img src="/files/6275ca0bc4087a4dd9e0a4760599742bcc0fab22" alt=""><figcaption></figcaption></figure>

{% hint style="info" %}
**Formula**

rOut\_Y = (((rX1-rIn\_X)\*(rY2-rY1))/(rX1-rX2))+rY1

**Constraints**

The analog value output *rOut\_Y* is of data type REAL. With an inappropriate selection of the parameters **rX1**, **rX2**, **rY1** and **rY2** as well as the value of the analog value input *rIn\_X* it can lead to exceeding the limits of the data type.
{% endhint %}

#### Enable / disable limits **xMinMaxLimit**

The limits of the analog value output *rOut\_Y* can generally be enabled and disabled with this setpoint / parameter.

| **xMinMaxLimit** | Limits            | Notes                                             |
| ---------------- | ----------------- | ------------------------------------------------- |
| FALSE            | none              | *rOut\_Y* without absolute limits                 |
| TRUE             | Y\_min and Y\_max | Limit of the analog value output *rOut\_Y* active |

#### Values of the limits **iMinMaxOffset**

The limits of the analog value output are only active if the setpoint / parameter **xMinMaxLimit** is active (= TRUE).\
The limit values Y\_min and Y\_max are then calculated as follows:

{% hint style="info" %}
**Formulas:**

Y\_min = rY1 - ((ABS(rY2-rY1))\*iMinMaxOffset)/100\
Y\_max = rY2 + ((ABS(rY2-rY1))\*iMinMaxOffset)/100\\
{% endhint %}

| *rY1* | *rY2* | *rY2* - *rY1* | **iMinMaxOffset** | *Y\_min* | *Y\_max* | Notes           |
| ----- | ----- | ------------- | ----------------- | -------- | -------- | --------------- |
| 0     | 100   | 100           | 0                 | 0        | 100      | Default limits  |
| 0     | 100   | 100           | 10                | -10      | 110      | Positive offset |
| 0     | 100   | 100           | -10               | 10       | 90       | Negative offset |

#### Digital output *xErr*

The digital output *xErr* signals an error during the conversion process. The following errors are considered:

* *rX1* AND *rX2* = 0
* *rX1* = *rX2*
* *rY1* AND *rY2* = 0
* *rY1* = *rY2*

| Error during the conversion process | *xErr* | Notes                               |
| ----------------------------------- | ------ | ----------------------------------- |
| FALSE                               | FALSE  | Conversion error-free               |
| TRUE                                | TRUE   | Error during the conversion process |

Legend: X = any

### CODESYS

InOut:

| Scope       | Name            | Type   | Initial |
| ----------- | --------------- | ------ | ------- |
| Input       | `rIn_X`         | `REAL` | 0       |
| Output      | `rOut_Y`        | `REAL` |         |
| Output      | `xErr`          | `BOOL` |         |
| Input Const | `iMinMaxOffset` | `INT`  | 0       |
| Input Const | `xMinMaxLimit`  | `BOOL` | FALSE   |
| Input Const | `rY2`           | `REAL` | 100     |
| Input Const | `rX2`           | `REAL` | 100     |
| Input Const | `rY1`           | `REAL` | 0       |
| Input Const | `rX1`           | `REAL` | 0       |


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