> ## Documentation Index
> Fetch the complete documentation index at: https://notevil.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# CAPLfunctionLINtpPreSend

[Open topic with navigation](../../../../../CANoeDEFamily.htm#Topics/CAPLFunctions/LIN/Functions/CAPLfunctionLINtpPreSend.md)

[CAPL Functions](../../CAPLfunctions.md) » [LIN](../CAPLfunctionsLINOverview.md) » LINtp\_PreSend

# LINtp\_PreSend

[Valid for](../../../Shared/FeatureAvailability.md): CANoe DE • CANoe4SW DE

**Note**\
This callback function is called every time a LIN message is scheduled to be sent. The function allows to change the message data.

**Caution**:\
Changing message data before they are sent can violate the TP protocol and lead to errors! Please make sure that the network can handle these situations!

## Function Syntax

```plaintext theme={null}
void LINtp_PreSend(byte data[]);
```

## Description

The callback function is called before a LIN message is sent with the provided data.

## Parameters

* **data**: Message data

## Return Values

—

## Example

```plaintext theme={null}
LINtp_PreSend(byte data[])
{
  // ...
  // change sequence number of the consecutive frame
  data[1] = data[1] + 1;
  // ...
}
```