TI中文支持网最近用MSP430FR2433+TMP112测试，发现一个很奇怪的问题，在读取TMP112的温度寄存器的2字节数据后，又有9个时钟信号，对应的·SDA一直是高电平，这时UCB0RXBUF里面会变成0xFF，而且必须把这个0xFF给读取出来，否则第二次读取的话发送开始信号后无法进入中断。一直没找到问题所在。
IIC驱动函数如下（参考官方例程）：
#include "iic.h"
/* Used to track the state of the software state machine*/
I2C_Mode MasterMode = IDLE_MODE;
/* The Register Address/Command to use*/
uint8_t TransmitRegAddr = 0;
/* ReceiveBuffer: Buffer used to receive data in the ISR
* RXByteCtr: Number of bytes left to receive
* ReceiveIndex: The index of the next byte to be received in ReceiveBuffer
* TransmitBuffer: Buffer used to transmit data in the ISR
* TXByteCtr: Number of bytes left to transfer
* TransmitIndex: The index of the next byte to be transmitted in TransmitBuffer
* */
uint8_t ReceiveBuffer[MAX_BUFFER_SIZE] = {0};
uint8_t RXByteCtr = 0;
uint8_t ReceiveIndex = 0;
uint8_t TransmitBuffer[MAX_BUFFER_SIZE] = {0};
uint8_t TXByteCtr = 0;
uint8_t TransmitIndex = 0;
//******************************************************************************
// Device Initialization *******************************************************
//******************************************************************************
void initI2C()
{UCB0CTLW0 = UCSWRST;// Enable SW resetUCB0CTLW0 |= UCMODE_3 | UCMST | UCSSEL__SMCLK | UCSYNC; // I2C master mode, SMCLKUCB0BRW = 0x000A;// fSCL = SMCLK/10 = ~100kHzUCB0I2CSA = SLAVE_ADDR;// Slave AddressUCB0CTLW0 &= ~UCSWRST;// Clear SW reset, resume operationUCB0IE |= UCNACKIE;
}
I2C_Mode I2C_Master_ReadReg(uint8_t dev_addr, uint8_t reg_addr, uint8_t count)
{/* Initialize state machine */MasterMode = TX_REG_ADDRESS_MODE;TransmitRegAddr = reg_addr;RXByteCtr = count;TXByteCtr = 0;ReceiveIndex = 0;TransmitIndex = 0;/* Initialize slave address and interrupts */UCB0I2CSA = dev_addr;UCB0IFG &= ~(UCTXIFG + UCRXIFG);// Clear any pending interruptsUCB0IE &= ~UCRXIE;// Disable RX interruptUCB0IE |= UCTXIE;// Enable TX interruptUCB0CTLW0 |= UCTR + UCTXSTT;// I2C TX, start condition__bis_SR_register(LPM0_bits + GIE);// Enter LPM0 w/ interrupts__no_operation();// Set breakpoint >>here<< andreturn MasterMode;
}
I2C_Mode I2C_Master_WriteReg(uint8_t dev_addr, uint8_t reg_addr, uint8_t *reg_data, uint8_t count)
{/* Initialize state machine */MasterMode = TX_REG_ADDRESS_MODE;TransmitRegAddr = reg_addr;//Copy register data to TransmitBufferCopyArray(reg_data, TransmitBuffer, count);TXByteCtr = count;RXByteCtr = 0;ReceiveIndex = 0;TransmitIndex = 0;/* Initialize slave address and interrupts */UCB0I2CSA = dev_addr;UCB0IFG &= ~(UCTXIFG + UCRXIFG);// Clear any pending interruptsUCB0IE &= ~UCRXIE;// Disable RX interruptUCB0IE |= UCTXIE;// Enable TX interruptUCB0CTLW0 |= UCTR + UCTXSTT;// I2C TX, start condition__bis_SR_register(LPM0_bits + GIE);// Enter LPM0 w/ interrupts__no_operation();// Set breakpoint >>here<< andreturn MasterMode;
}
I2C_Mode I2C_Master_ReadData(uint8_t dev_addr, uint8_t count)
{/* Initialize state machine */MasterMode = RX_DATA_MODE;RXByteCtr = count;TXByteCtr = 0;ReceiveIndex = 0;TransmitIndex = 0;/* Initialize slave address and interrupts */UCB0I2CSA = dev_addr;UCB0IFG &= ~(UCTXIFG + UCRXIFG);// Clear any pending interruptsUCB0IE |= UCRXIE;// Disable RX interruptUCB0CTLW0 &= ~UCTR;// Switch to receiverwhile (UCB0CTL1 & UCTXSTP);// Ensure stop condition got sentUCB0CTLW0 |= UCTXSTT;// I2C RX, start condition__bis_SR_register(LPM0_bits + GIE);// Enter LPM0 w/ interrupts__no_operation();// Set breakpoint >>here<< andreturn MasterMode;
}
void CopyArray(uint8_t *source, uint8_t *dest, uint8_t count)
{uint8_t copyIndex = 0;for (copyIndex = 0; copyIndex < count; copyIndex++){dest[copyIndex] = source[copyIndex];}
}
//******************************************************************************
// I2C Interrupt ***************************************************************
//******************************************************************************
#if defined(__TI_COMPILER_VERSION__) || defined(__IAR_SYSTEMS_ICC__)
#pragma vector = USCI_B0_VECTOR
__interrupt void USCI_B0_ISR(void)
#elif defined(__GNUC__)
void __attribute__ ((interrupt(USCI_B0_VECTOR))) USCI_B0_ISR (void)
#else
#error Compiler not supported!
#endif
{//Must read from UCB0RXBUFuint8_t rx_val = 0;switch(__even_in_range(UCB0IV, USCI_I2C_UCBIT9IFG)){case USCI_NONE:break;// Vector 0: No interruptscase USCI_I2C_UCALIFG:break;// Vector 2: ALIFGcase USCI_I2C_UCNACKIFG:// Vector 4: NACKIFGUCB0CTL1 |= UCTXSTP;// I2C start conditionUCB0IFG = 0;// Clear All USCI_B0 flags__bic_SR_register_on_exit(LPM0_bits);// Exit LPMMasterMode = NACK_MODE;// State state is to receive databreak;case USCI_I2C_UCSTTIFG: break;// Vector 6: STTIFGcase USCI_I2C_UCSTPIFG: break;// Vector 8: STPIFGcase USCI_I2C_UCRXIFG3: break;// Vector 10: RXIFG3case USCI_I2C_UCTXIFG3: break;// Vector 12: TXIFG3case USCI_I2C_UCRXIFG2: break;// Vector 14: RXIFG2case USCI_I2C_UCTXIFG2: break;// Vector 16: TXIFG2case USCI_I2C_UCRXIFG1: break;// Vector 18: RXIFG1case USCI_I2C_UCTXIFG1: break;// Vector 20: TXIFG1case USCI_I2C_UCRXIFG0:// Vector 22: RXIFG0rx_val = UCB0RXBUF;if (RXByteCtr){ReceiveBuffer[ReceiveIndex++] = rx_val;RXByteCtr--;}if (RXByteCtr == 1){UCB0CTLW0 |= UCTXSTP;}else if (RXByteCtr == 0){UCB0IE &= ~UCRXIE;//UCB0IFG &=~ UCRXIFG;rx_val = UCB0RXBUF; //这个地方不能注释，要把UCB0RXBUF里面的0xff读出来，不然连续会进不了中断MasterMode = IDLE_MODE;__bic_SR_register_on_exit(LPM0_bits);// Exit LPM0}break;case USCI_I2C_UCTXIFG0:// Vector 24: TXIFG0switch (MasterMode){case TX_REG_ADDRESS_MODE:UCB0TXBUF = TransmitRegAddr;if (RXByteCtr)MasterMode = SWITCH_TO_RX_MODE;// Need to start receiving nowelseMasterMode = TX_DATA_MODE;// Continue to transmision with the data in Transmit Bufferbreak;case SWITCH_TO_RX_MODE:UCB0IE |= UCRXIE;// Enable RX interruptUCB0IE &= ~UCTXIE;// Disable TX interruptUCB0CTLW0 &= ~UCTR;// Switch to receiverMasterMode = RX_DATA_MODE;// State state is to receive dataUCB0CTLW0 |= UCTXSTT;// Send repeated startif (RXByteCtr == 1){//Must send stop since this is the N-1 bytewhile((UCB0CTLW0 & UCTXSTT));UCB0CTLW0 |= UCTXSTP;// Send stop condition}break;case TX_DATA_MODE:if (TXByteCtr){UCB0TXBUF = TransmitBuffer[TransmitIndex++];TXByteCtr--;}else{//Done with transmissionUCB0CTLW0 |= UCTXSTP;// Send stop conditionMasterMode = IDLE_MODE;UCB0IE &= ~UCTXIE;// disable TX interrupt__bic_SR_register_on_exit(LPM0_bits);// Exit LPM0}break;default:__no_operation();break;}break;default: break;}
}
读取函数如下:
void Tmp102_Read_Temp()
{I2C_Mode TempMode = IDLE_MODE;uint8_t reg_data = 0x00;//I2C_Master_ReadReg(TMP102_ADDRESS, Temperature , 2);//也可单独能出结果，但是在发送寄存器地址后没有STOP操作与TMP112时序对不上，查看了TMP117的时序在发送寄存器地址后可以直接RESTART，不用STOP操作I2C_Master_WriteReg(TMP102_ADDRESS, Temperature, 0 , 0);I2C_Master_ReadData(TMP102_ADDRESS , 2);
//while(1)
//{
//TempMode = I2C_Master_WriteReg(TMP102_ADDRESS, Temperature, 0 , 0);
//TempMode = I2C_Master_ReadData(TMP102_ADDRESS , 2);
//__delay_cycles(10000);
//}
}
Susan Yang：
请问上拉电阻的值是多少？根据TMP112数据表，应为5 kOhm 。还有一些注意事项：
1应该实施OSCFault标志检查，如下所示
do
{IFG1 &= ~OFIFG;// Clear OSCFault flagfor (i = 0xFF; i > 0; i–);// Time for flag to set
}
while (IFG1 & OFIFG);// OSCFault flag still set?2在发送启动条件之前，请确保已发送停止条件（while (UCB0CTL1 & UCTXSTP);）。发送停止条件相同。
3 您只发送一个从设备地址，后跟一个字节（指针寄存器），而没有发送任何数据字节。然后，在发送停止条件之前过渡到接收模式。这很可能是您仅收到0xFF响应的原因。
