Serial Receive Callback

Serial Receive Callback Example

Overview

This NetBurner embedded application demonstrates how to register a custom callback function to intercept and handle serial port receive processing. The example shows how to bypass the default system serial receive handling and implement custom processing using a circular buffer.

Application Description

The application creates a serial receive callback system that:

• Opens serial port 1 at 115200 baud rate
• Registers a custom callback function to handle incoming serial data
• Uses a circular buffer to store received data
• Continuously processes and displays received characters

Key Features

Serial Receive Callback

• Function: SerialReceiveCallback(int uartNum, unsigned char dataByte)
• Purpose: Intercepts serial data at the interrupt level
• Restrictions: Called from interrupt context - no I/O functions allowed, only RTOS post functions

Circular Buffer Implementation

• Size: 256 bytes (RX_BUF_SIZE)
• Variables:
  • indexGet: Read pointer for the circular buffer
  • indexPut: Write pointer for the circular buffer
  • CircBufferArray: The actual buffer storage
• Buffer Management: Automatically wraps around when reaching buffer limits

Main Processing Loop

• Opens serial port 1 at 115200 baud
• Assigns the custom callback to UART1 receive processing
• Continuously reads from the circular buffer and displays characters
• Uses OSTimeDly(1) for task scheduling

Hardware Requirements

• NetBurner embedded device with UART1 capability
• Serial connection to UART1 at 115200 baud rate

Code Structure

main.cpp
  Headers and includes
  Global variables (circular buffer)
  SerialReceiveCallback() - Interrupt-level callback
  UserMain() - Main application loop

Important Notes

Interrupt Context Limitations

The SerialReceiveCallback function operates in interrupt context, which means:

• No standard I/O functions (printf, iprintf, etc.) can be called
• Only RTOS post functions are safe to use
• Keep processing minimal and fast

Buffer Overflow Handling

The circular buffer implements a simple overflow strategy:

• When the buffer is full, the oldest data is overwritten
• Both read and write pointers automatically wrap around

System Diagnostics

The application enables system diagnostics with EnableSystemDiagnostics(). This should be removed for production code.

Usage

1. Compile and flash the application to a NetBurner device
2. Connect a serial terminal to UART1 at 115200 baud
3. Send data to the serial port
4. Observe the echoed characters in the application output

Build Information

The application displays build timestamp information on startup, showing when the code was compiled.