Start and stop conditions in Embedded C

Introduction

Start and stop conditions tell devices when to begin and end communication on a shared wire. They help devices talk without confusion.

When you want to begin sending data to a device on a shared bus like I2C.

When you want to end communication cleanly so other devices can use the bus.

When multiple devices share the same communication lines and need clear signals to avoid data mix-up.

Syntax

Embedded C

void I2C_StartCondition(void);
void I2C_StopCondition(void);

Start condition usually means pulling the data line low while clock is high.

Stop condition usually means releasing the data line to high while clock is high.

Examples

This example shows starting communication, sending data, then stopping communication.

Embedded C

I2C_StartCondition();
// Send address or data
I2C_StopCondition();

Sometimes a repeated start is used to keep control of the bus without stopping.

Embedded C

I2C_StartCondition();
// Repeated start without stop
I2C_StartCondition();

Sample Program

This program simulates the start and stop conditions in I2C communication by printing messages. It shows the order of operations in a simple way.

Embedded C

#include <stdio.h>

// Simulated functions for start and stop conditions
void I2C_StartCondition(void) {
    printf("Start condition: SDA goes LOW while SCL is HIGH\n");
}

void I2C_StopCondition(void) {
    printf("Stop condition: SDA goes HIGH while SCL is HIGH\n");
}

int main() {
    printf("Begin I2C communication\n");
    I2C_StartCondition();
    printf("Send device address and data here\n");
    I2C_StopCondition();
    printf("End I2C communication\n");
    return 0;
}

Important Notes

Start and stop conditions are important for devices to know when to listen or ignore the bus.

In real hardware, these conditions are created by changing voltage levels on wires.

Summary

Start condition signals the beginning of communication.

Stop condition signals the end of communication.

They help multiple devices share the same communication lines without errors.