我用两个g2553做IIC通信

Bill Kent

Prodigy 120 points

Other Parts Discussed in Thread: MSP430G2553

都用的是LaunchPad开发板

一个主机一个从机。主机例程是官方的msp430g2xx3_usciB0_i2c_04,从机是msp430g2xx3_usciB0_i2c_05。

现在的问题是主机死在while (UCB0CTL1 & UCTXSTT); // Start condition sent?

从机死在这一句 __bis_SR_register(CPUOFF + GIE); // Enter LPM0 w/ interrupts的前面。

电路按照例程要求做好了，两个上拉电阻1K（没有10K的电阻）。

软件用的是CCS_V5.1。

示波器上SCL,SDA有信号，但不是时钟信号。

请问为什么？

13 年多前

0 Bill Kent 13 年多前

Prodigy 120 points

电路按照例程要求做好了，两个共地，下拉电阻100K（没有10K的电阻）。

0 Young Hu 13 年多前

TI__Mastermind 29385 points

您好！

建议做如下检查：

1、检查硬件的连线；

2、用示波器抓一下图，看看数据线和时钟线上有没有信号。

然后把结果发上来，大家帮您看看。

0 Bill Kent 13 年多前回复 Bill Kent

Prodigy 120 points

我现在是两台电脑（win7，32位）同时分别控制两个板，软件都用的是CCS_V5.1

0 Bill Kent 13 年多前回复 Young Hu

Prodigy 120 points

一直是低，没有信号。请问一下，是应该接上拉，还是下拉电阻。

0 Hardy Hu 13 年多前

TI__Genius 9431 points

这里有个例程可以试试，再结合自己的代码看看：

//******************************************************************************

// MSP430G2xx3 Demo - USCI_B0 I2C Master RX single bytes from MSP430 Slave

// Description: This demo connects two MSP430's via the I2C bus. The master

// reads from the slave. This is the master code. The data from the slave

// transmitter begins at 0 and increments with each transfer. The received

// data is in R5 and is checked for validity. If the received data is

// incorrect, the CPU is trapped and the P1.0 LED will stay on. The USCI_B0

// RX interrupt is used to know when new data has been received.

// ACLK = n/a, MCLK = SMCLK = BRCLK = default DCO = ~1.2MHz

// /|\ /|\

// MSP430G2xx3 10k 10k MSP430G2xx3

// slave | | master

// ----------------- | | -----------------

// -|XIN P1.7/UCB0SDA|<-|---+->|P1.7/UCB0SDA XIN|-

// | | | | | 32kHz

// -|XOUT | | | XOUT|-

// | P1.6/UCB0SCL|<-+----->|P1.6/UCB0SCL |

// | | | P1.0|--> LED

// D. Dang

// Texas Instruments Inc.

// February 2011

// Built with CCS Version 4.2.0 and IAR Embedded Workbench Version: 5.10

//******************************************************************************

#include "msp430g2553.h"

unsigned char RXData;

unsigned char RXCompare;

void main(void)

{

WDTCTL = WDTPW + WDTHOLD; // Stop WDT

P1OUT &= ~BIT0; // P1.0 = 0

P1DIR |= BIT0; // P1.0 output

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 = 0x048; // Slave Address is 048h

UCB0CTL1 &= ~UCSWRST; // Clear SW reset, resume operation

IE2 |= UCB0RXIE; // Enable RX interrupt

RXCompare = 0; // Used to check incoming data

while (1)

{

while (UCB0CTL1 & UCTXSTP); // Ensure stop condition got sent

UCB0CTL1 |= UCTXSTT; // I2C start condition

while (UCB0CTL1 & UCTXSTT); // Start condition sent?

UCB0CTL1 |= UCTXSTP; // I2C stop condition

__bis_SR_register(CPUOFF + GIE); // Enter LPM0 w/ interrupts

if (RXData != RXCompare) // Trap CPU if wrong

{

P1OUT |= BIT0; // P1.0 = 1

while (1); // Trap CPU

}

RXCompare++; // Increment correct RX value

}

// USCI_B0 Data ISR

#pragma vector = USCIAB0TX_VECTOR

__interrupt void USCIAB0TX_ISR(void)

{

RXData = UCB0RXBUF; // Get RX data

__bic_SR_register_on_exit(CPUOFF); // Exit LPM0

}

0 Hardy Hu 13 年多前

TI__Genius 9431 points

//******************************************************************************

// MSP430G2xx3 Demo - USCI_B0 I2C Slave TX single bytes to MSP430 Master

// Description: This demo connects two MSP430's via the I2C bus. The master

// reads from the slave. This is the slave code. The TX data begins at 0

// and is incremented each time it is sent. An incoming start condition

// is used as a trigger to increment the outgoing data. The master checks the

// data it receives for validity. If it is incorrect, it stops communicating

// and the P1.0 LED will stay on. The USCI_B0 TX interrupt is used to know

// when to TX.

// ACLK = n/a, MCLK = SMCLK = default DCO = ~1.2MHz

// /|\ /|\

// MSP430G2xx3 10k 10k MSP430G2xx3

// slave | | master

// ----------------- | | -----------------

// -|XIN P1.7/UCB0SDA|<-|---+->|P1.7/UCB0SDA XIN|-

// | | | | |

// -|XOUT | | | XOUT|-

// | P1.6/UCB0SCL|<-+----->|P1.6/UCB0SCL |

// | | | P1.0|--> LED

// D. Dang

// Texas Instruments Inc.

// February 2011

// Built with CCS Version 4.2.0 and IAR Embedded Workbench Version: 5.10

//******************************************************************************

#include "msp430g2553.h"

unsigned char TXData;

void main(void)

{

WDTCTL = WDTPW + WDTHOLD; // Stop WDT

P1DIR |= BIT0; // P1.0 output

P1SEL |= BIT6 + BIT7; // Assign I2C pins to USCI_B0

P1SEL2|= BIT6 + BIT7; // Assign I2C pins to USCI_B0

UCB0CTL1 |= UCSWRST; // Enable SW reset

UCB0CTL0 = UCMODE_3 + UCSYNC; // I2C Slave, synchronous mode

UCB0I2COA = 0x48; // Own Address is 048h

UCB0CTL1 &= ~UCSWRST; // Clear SW reset, resume operation

UCB0I2CIE |= UCSTTIE; // Enable STT interrupt

IE2 |= UCB0TXIE; // Enable TX interrupt

TXData = 0xff; // Used to hold TX data

while (1)

{

__bis_SR_register(CPUOFF + GIE); // Enter LPM0 w/ interrupts

}

// USCI_B0 Data ISR

#pragma vector = USCIAB0TX_VECTOR

__interrupt void USCIAB0TX_ISR(void)

{

UCB0TXBUF = TXData; // TX data

__bic_SR_register_on_exit(CPUOFF); // Exit LPM0

}

// USCI_B0 State ISR

#pragma vector = USCIAB0RX_VECTOR

__interrupt void USCIAB0RX_ISR(void)

{

UCB0STAT &= ~UCSTTIFG; // Clear start condition int flag

TXData++; // Increment data

}

0 Hardy Hu 13 年多前

TI__Genius 9431 points

电阻应该是上拉，100K有点太大了，换成小一点的，上升沿会陡峭一些

0 Peter_Zheng 13 年多前

TI__Expert 8395 points

i2c两线用电阻上拉。我调试过例程程序，通信没有问题。

0 Hardy Hu 13 年多前

TI__Genius 9431 points

1.下拉会使SDA,SCL都hold住，IIC停止工作，IIC的SDA.SCL的无效态是高，一定要上拉；

2.需要注意的是在正常通讯时，SCL为高时，SDA数据有效，这时SDA数据要保持恒定，在SCL为低时，进行数据更新等操作；

0 Bill Kent 13 年多前回复 Hardy Hu

Prodigy 120 points

还是不行，谢谢大家的回答。

0 Hardy Hu 13 年多前回复 Bill Kent

TI__Genius 9431 points

还是死在while (UCB0CTL1 & UCTXSTT); // Start condition sent?吗？

抓两个波形给大家看看嘛

0 Jinxiong Zhan 12 年多前回复 Peter_Zheng

Prodigy 60 points

管脚按要求接好，，可是没有响应aclk，调了几天，，没反应啊

0 terry terry 12 年多前回复 Peter_Zheng

Prodigy 53 points

请问msp430内部和launchpad板子上在i2c接口都是没有上拉电阻的吗？还要自己外接是吗？

0 Triton Zhang 12 年多前回复 terry terry

TI__Expert 7790 points

MSP430的GPIO是有弱上拉功能的，但该功能只在GPIO模式下有用。你使能管脚为I2C功能后，按照I2C的协议规定I2C的管脚属性为开漏管脚，所以，必须外接上拉电阻。

在发送数据的时候，由于是开漏管脚，高电平都是被上拉电阻拉到高电平的。如果用下拉电阻，高电平就会变成无效信号。你使用示波器应该在SDA和SCL管脚上测量不到信号。

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我用两个g2553做IIC通信