MSP430硬件I2C实现SMBus通信详解

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本篇应用报告SLAA249A详细介绍了如何在MSP430硬件I2C模块上实现系统管理总线(SMBus)。SMBus是一种广泛应用于智能电池、电源相关设备以及各类系统设备间通信的接口标准，支持主从通信协议。报告的主要内容包括： 1. **引言**：开始部分概述了SMBus的基本概念，它是基于I2C（Inter-Integrated Circuit）协议的两线串行接口，使用SCL（Serial Clock）和SDA（Serial Data）线进行数据传输，通过VCC上的上拉电阻连接。 2. **SMBus协议**：本节介绍了SMBus的协议特性，包括时序规则、地址寻址方式以及不同的数据传输模式，如标准模式、快速模式和高速模式，这些都对实现硬件I2C接口的兼容性和效率至关重要。 3. **软件实现**：报告详细阐述了在MSP430硬件平台上实现SMBus通信所需的软件策略，可能涉及到中断处理、错误检测和恢复、以及数据包发送和接收的控制逻辑。这包括编写驱动程序和用户应用程序，确保与不同类型的SMBus设备正确交互。 4. **示例代码**：该部分提供了四个具体的代码示例，分别展示了如何实现MSP430作为SMBus主设备与多个从设备（如MSP430F169与TM175）之间的通信。每个示例展示了基本的初始化过程、数据交换以及错误处理机制。 - 示例1：展示主设备控制其他设备的通信流程。 - 示例2：涉及主设备读取从设备状态或配置参数。 - 示例3：更复杂的通信场景，可能涉及多轮数据交换和命令响应。 - 示例4：可能包含一种特定的电源管理或监控功能的实现。 5. **结论**：报告总结了MSP430硬件I2C实现SMBus的关键要点和技术挑战，以及在实际应用中的优势和局限性。它强调了良好的设计和测试对于确保稳定可靠通信的重要性。 6. **参考文献**：提供了参考资料列表，供读者进一步深入学习SMBus和MSP430硬件I2C的相关技术。 7. **附录A**：进一步讨论了如何利用MSP430的Universal Serial Communication Interface (USIC) I2C外设来实现SMBus，这部分内容有助于开发者了解不同硬件选项的差异。 8. **图表**：本文提供了几个关键图示，直观地展示了硬件连接、信号波形和操作流程，便于理解和实现。通过阅读这篇报告，开发人员可以掌握如何有效地在MSP430平台上构建兼容SMBus的硬件和软件系统，从而实现高效、稳定的设备间通信。

Application Report

SLAA249A–April 2005–Revised October 2009

Implementing SMBus Using MSP430 Hardware I

Harman Grewal .................................................................................................................... MSP430

ABSTRACT

This application report describes the implementation of the system management bus (SMBus) using the

MSP430 hardware I

C peripheral. SMBus is used as a communication link for smart batteries,

power-related devices, and a wide variety of other system devices. This report includes the support for

master and slave protocols in a SMBus communication system.

Contents

1 Introduction .................................................................................................................. 1

2 SMBus Protocols ............................................................................................................ 2

3 Software ...................................................................................................................... 2

4 Example Code ............................................................................................................... 3

4.1 Example 1 ........................................................................................................... 3

4.2 Example 2 ........................................................................................................... 3

4.3 Example 3 ........................................................................................................... 3

4.4 Example 4 ........................................................................................................... 4

5 Conclusion ................................................................................................................... 4

6 References ................................................................................................................... 4

Appendix A SMBus Using the USCI I

C Peripheral .......................................................................... 5

List of Figures

1 MSP430F169 Master-Slave SMBus Communication .................................................................. 2

2 MSP430F169 Master-TMP175 Slave SMBus Communication ....................................................... 4

1 Introduction

SMBus is a two-wire serial interface based on the principles of I

C. The two lines are serial clock (SCL)

and serial data (SDA), which are tied to V

using pullup resistors. The devices communicating on this bus

can drive the lines low or release them to high impedance. This connection is a wired-AND configuration.

Multiple I

C/SMBus devices can be connected on the bus, but MSP430 pins should not be pulled above

. For example, if the V

of the MSP430 is at 3 V, then all devices on the bus must be pulled up to only

3 V.

A device performing data transfers on the bus can be considered as a master or a slave. Each master and

slave device can either be a transmitter (send data) or a receiver (receive data), and the communication

on the bus is always initiated by the master by providing a valid start condition and the SCL signal.

Multiple master and slave devices may be connected on the bus, but only one device may master the bus

during a data transfer. Since more than one master may simultaneously attempt to take control of the bus

and start a transmission, the I

C/SMBus protocol provides an arbitration mechanism that relies on the

wired-AND connection of all devices to the bus. A master device that generates a logic high on the SDA

bus loses arbitration to a master that generates a logic low on the data bus. The MSP430 master

transmitter that loses arbitration switches to slave receiver mode and sets the arbitration lost flag, ALIFG.

[1] Each device on the bus has a unique 7-bit address, which allows a total of 128 devices to be

connected on the bus. Some addresses are dedicated SMBus addresses that are reserved and must not

be assigned to any SMBus device; for example, the SMBus Alert response address (0001 100b). [2]

SLAA249A–April 2005–Revised October 2009

Implementing SMBus Using MSP430 Hardware I

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