TI中文支持网大家好，我在使用LaunchPad msp430g2553的硬件I2C的时候遇到很多问题。我把CCSV5中提供的读PCF8574的历程下到板子上之后没有办法使用，上拉电阻我也接了，历程一点也没有改，已经确定硬件没有问题，但还是没法用，有谁能给我提供一个可以使用的历程或者是告诉我在使用硬件I2C的时候应该如何配置以及需要注意些什么问题吗？谢谢~\(≧▽≦)/~啦啦啦
Hardy Hu：
你好！最好提供一些测试的结果给大家，才能够有效的帮到你。
比如IIC总线的波形等。还有就是最好先进行一些分析，进行有针对性的提问。
Eminence Monkey：
回复 Hardy Hu:
我是示波器观察到SCL总线一直处于低电平状态，在寄存器查看窗口看到UCB0STAT状态寄存器中的忙位一直为1，而且我在发送中断中设置断点之后 ，程序不能进入中断中在断点处停下来。这都是因为什么？
Eminence Monkey：
回复 Hardy Hu:
Hardy Hu ，你好，
我用示波器观察到SCL总线一直处于低电平状态，在寄存器查看窗口看到UCB0STAT状态寄存器中的忙位一直为1，而且我在发送中断中设置断点之后 ，程序不能进入中断中在断点处停下来。这都是因为什么？
kqian0327：
Hello,
我觉得还是IIC没有配置好的原因。
你可以下载MSP430WARE软件库在里面找到需要的430所有的参考代码。
如果你已经下载CCS,那么在CCS View ->TI resource 里面可以找到 MSP430WARE 插件
下面是我在里面找到的一个关于总线IIC读取外部ADC数据的例程供你参考：
/* –COPYRIGHT–,BSD_EX * Copyright (c) 2012, Texas Instruments Incorporated * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * * Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * * * Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * * Neither the name of Texas Instruments Incorporated nor the names of * its contributors may be used to endorse or promote products derived * from this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. * ******************************************************************************* * * MSP430 CODE EXAMPLE DISCLAIMER * * MSP430 code examples are self-contained low-level programs that typically * demonstrate a single peripheral function or device feature in a highly * concise manner. For this the code may rely on the device's power-on default * register values and settings such as the clock configuration and care must * be taken when combining code from several examples to avoid potential side * effects. Also see www.ti.com/grace for a GUI- and www.ti.com/msp430ware * for an API functional library-approach to peripheral configuration. * * –/COPYRIGHT–*///******************************************************************************// MSP430G2xx3 Demo – USCI_B0 I2C Master Interface to DAC8571, Write//// Description: Using UCB0TXIE, a continuous sine wave is output to the// external DAC using a 16-point look-up table. Only one start condition// is executed. Data is handled by the ISR and the CPU is normally in LPM0.// ACLK = n/a, MCLK = SMCLK = BRCLK = default DCO = ~1.2MHz//// MSP430G2xx3 DAC8571// —————— ————// -|XIN P1.7/UCB0SDA|<—————>|SDA |// | P1.6/UCB0SCL|—————->|SCL I2C |// -|XOUT | | SLAVE |// | I2C MASTER | GND|A0 |////// DAC8571 I2C address = 0x4C (A0 = GND)//// D. Dang// Texas Instruments Inc.// February 2011// Built with CCS Version 4.2.0 and IAR Embedded Workbench Version: 5.10//******************************************************************************#include <msp430.h>
const unsigned char Sine_Tab[] = // 16 Point 16-bit Sine Table{ 0xFF, // MSB Word 0 0xFF, // LSB 0xF6, // MSB Word 1 0x40, // LSB 0xDA, // MSB Word 2 0x81, // LSB 0xB0, // MSB Word 3 0xFA, // LSB 0x7F, // MSB Word 4 0xFF, // LSB 0x4F, // MSB Word 5 0x03, // LSB 0x25, // MSB Word 6 0x7C, // LSB 0x09, // MSB Word 7 0xBD, // LSB 0x00, // MSB Word 8 0x00, // LSB 0x09, // MSB Word 9 0xBD, // LSB 0x25, // MSB Word 10 0x7C, // LSB 0x4F, // MSB Word 11 0x03, // LSB 0x7F, // MSB Word 12 0xFE, // LSB 0xB0, // MSB Word 13 0xFA, // LSB 0xDA, // MSB Word 14 0x81, // LSB 0xF6, // MSB Word 15 0x40 // LSB};
int main(void){ WDTCTL = WDTPW + WDTHOLD; // Stop Watchdog Timer P1SEL |= BIT6 + BIT7; // Assign I2C pins to USCI_B0 P1SEL2|= BIT6 + BIT7; // Assign I2C pins to USCI_B0 UCB0CTL1 |= UCSWRST; // Enable SW reset UCB0CTL0 = UCMST + UCMODE_3 + UCSYNC; // I2C Master, synchronous mode UCB0CTL1 = UCSSEL_2 + UCSWRST; // Use SMCLK, keep SW reset UCB0BR0 = 12; // fSCL = SMCLK/12 = ~100kHz UCB0BR1 = 0; UCB0I2CSA = 0x4c; // Set slave address UCB0CTL1 &= ~UCSWRST; // Clear SW reset, resume operation IE2 |= UCB0TXIE; // Enable TX ready interrupt UCB0CTL1 |= UCTR + UCTXSTT; // I2C TX, start condition UCB0TXBUF = 0x010; // Write DAC control byte __bis_SR_register(CPUOFF + GIE); // Enter LPM0 w/ interrupts}
// USCI_B0 Data ISR#pragma vector = USCIAB0TX_VECTOR__interrupt void USCIAB0TX_ISR(void){ static unsigned char ByteCtr;
UCB0TXBUF = Sine_Tab[ByteCtr++]; // Transmit data byte ByteCtr &= 0x1f; // Do not exceed table}
Triton Zhang：
如果你确实没有更改例程代码，建议你从硬件方面检查问题。下面给你列个如何查找问题的思路。你可以按照下面一条一条地对照操作。看问题处在第几步。
1. i2c的sda和scl口线需要有10-20k上拉电阻。（这点你已经确定了）
2. 断开从机，初始化i2c模块，用示波器看sda和scl口线电平，这个时候两个口线应该是高电平。
3. 连接从机在测量sda和scl的电平，如果这个时候口线保持为高就没问题，如果变低了，就说明从机有问题。
4. 断点设置到发送start之后， 用示波器观察信号是否能正确发出。
5. 断点设置到发送一个数据之后，用示波器观察是否有一字节数据发出，第9位是否为低电平。
Eminence Monkey：
回复 Triton Zhang:
Triton Zhang ，
你好，我断开从机，初始化I2C模块后，用示波器观察sda和scl均为低电平，这说明哪里有问题呢？
Triton Zhang：
回复 Eminence Monkey:
1. 正常情况应该是初始化成功后口线为高。
2. 检查下上拉。
3. 检查下焊接，或换个芯片。
