TI中文支持网我选用的外部eeprom是24c64，之前所用单片机是使用usci模块完成的，但是在g系列只有usi模块，请问只种情况下如何控制外部eeprom，能否提供一些关键代码，谢谢
Young Hu：
24C64是I2C接口的，USI接口是支持I2C的，您可以参考USCI的代码进行修改
Yujie Liu：
回复 Young Hu:
现在是握手信号ACK总是收不到，您有例程可以让我参考一下么？
Young Hu：
回复 Yujie Liu:
我这边倒是没有针对24C64的参考代码。建议您使用示波器抓图，确定是软件问题还是硬件问题。
Peter_Zheng：
回复 Young Hu:
例程你可以去TI主页上对应该芯片的资料里找到code example。ACK收不到，查看是电路是否正确，上拉电阻是否连上，速率是否一致。
Yujie Liu：
回复 Young Hu:
谢谢您的回答，已经用f2112做了，感觉g系列还是不好用
Yujie Liu：
回复 Peter_Zheng:
谢谢您的回答，已经用f2112做了，感觉g系列还是不好用
Leon Yan：
回复 Yujie Liu:
G2xxx是性价比极高的系列，楼主还需要耐心啊，可以省钱不少，下面是代码，请查看。
//******************************************************************************// MSP430G2x21/G2x31 Demo – I2C Master Transmitter / Reciever, multiple bytes//// Description: I2C Master communicates with I2C Slave using// the USI. Master data should increment from 0x55 with each transmitted byte// and Master determines the number of bytes recieved, set by // the Number_of_Bytes value. LED off for address or data Ack; // LED on for address or data NAck.// ACLK = n/a, MCLK = SMCLK = Calibrated 1MHz////// ***THIS IS THE MASTER CODE***//// Slave Master// (msp430g2x21_usi_15.c)// MSP430G2x21/G2x31 MSP430G2x21/G2x31// —————– —————–// /|\| XIN|- /|\| XIN|-// | | | | | |// –|RST XOUT|- –|RST XOUT|-// | | | |// LED <-|P1.0 | | |// | | | P1.0|-> LED// | SDA/P1.7|——->|P1.6/SDA |// | SCL/P1.6|<——-|P1.7/SCL |//// Note: internal pull-ups are used in this example for SDA & SCL//// D. Dang// Texas Instruments Inc.// October 2010// Built with CCS Version 4.2.0 and IAR Embedded Workbench Version: 5.10//******************************************************************************#include <msp430g2221.h>#define number_of_bytes 5 // How many bytes?void Master_Transmit(void);void Master_Recieve(void);void Setup_USI_Master_TX(void);void Setup_USI_Master_RX(void);char MST_Data = 0x55; // Variable for transmitted datachar SLV_Addr = 0x90; int I2C_State, Bytecount, Transmit = 0; // State variablevoid Data_TX (void);void Data_RX (void);void main(void){ volatile unsigned int i; // Use volatile to prevent removal WDTCTL = WDTPW + WDTHOLD; // Stop watchdog if (CALBC1_1MHZ ==0xFF || CALDCO_1MHZ == 0xFF) { while(1); // If calibration constants erased // do not load, trap CPU!! } BCSCTL1 = CALBC1_1MHZ; // Set DCO DCOCTL = CALDCO_1MHZ; P1OUT = 0xC0; // P1.6 & P1.7 Pullups, others to 0 P1REN |= 0xC0; // P1.6 & P1.7 Pullups P1DIR = 0xFF; // Unused pins as outputs P2OUT = 0; P2DIR = 0xFF; while(1) { Master_Transmit(); _NOP(); // Used for IAR Master_Recieve(); _NOP(); }}/******************************************************// USI interrupt service routine// Data Transmit : state 0 -> 2 -> 4 -> 10 -> 12 -> 14// Data Recieve : state 0 -> 2 -> 4 -> 6 -> 8 -> 14******************************************************/#pragma vector = USI_VECTOR__interrupt void USI_TXRX (void){ switch(__even_in_range(I2C_State,14)) { case 0: // Generate Start Condition & send address to slave P1OUT |= 0x01; // LED on: sequence start Bytecount = 0; USISRL = 0x00; // Generate Start Condition… USICTL0 |= USIGE+USIOE; USICTL0 &= ~USIGE; if (Transmit == 1){ USISRL = 0x90; // Address is 0x48 << 1 bit + 0 (rw) } if (Transmit == 0){ USISRL = 0x91; // 0x91 Address is 0x48 << 1 bit // + 1 for Read } USICNT = (USICNT & 0xE0) + 0x08; // Bit counter = 8, TX Address I2C_State = 2; // next state: rcv address (N)Ack break; case 2: // Receive Address Ack/Nack bit USICTL0 &= ~USIOE; // SDA = input USICNT |= 0x01; // Bit counter=1, receive (N)Ack bit I2C_State = 4; // Go to next state: check (N)Ack break; case 4: // Process Address Ack/Nack & handle data TX if(Transmit == 1){ USICTL0 |= USIOE; // SDA = output if (USISRL & 0x01) // If Nack received… { // Send stop… USISRL = 0x00; USICNT |= 0x01; // Bit counter=1, SCL high, SDA low I2C_State = 14; // Go to next state: generate Stop P1OUT |= 0x01; // Turn on LED: error } else { // Ack received, TX data to slave… USISRL = MST_Data++; // Load data byte USICNT |= 0x08; // Bit counter = 8, start TX I2C_State = 10; // next state: receive data (N)Ack Bytecount++; P1OUT &= ~0x01; // Turn off LED break; } } if(Transmit == 0){ if (USISRL & 0x01) // If Nack received { // Prep Stop Condition USICTL0 |= USIOE; USISRL = 0x00; USICNT |= 0x01; // Bit counter= 1, SCL high, SDA low I2C_State = 8; // Go to next state: generate Stop P1OUT |= 0x01; // Turn on LED: error } else{ Data_RX();} // Ack received } break;case 6: // Send Data Ack/Nack bit USICTL0 |= USIOE; // SDA = output if (Bytecount <= number_of_bytes-2) { // If this is not the last byte USISRL = 0x00; // Send Ack P1OUT &= ~0x01; // LED off I2C_State = 4; // Go to next state: data/rcv again Bytecount++; } else //last byte: send NACK { USISRL = 0xFF; // Send NAck P1OUT |= 0x01; // LED on: end of comm I2C_State = 8; // stop condition } USICNT |= 0x01; // Bit counter = 1, send (N)Ack bit break; case 8: // Prep Stop Condition USICTL0 |= USIOE; // SDA = output USISRL = 0x00; USICNT |= 0x01; // Bit counter= 1, SCL high, SDA low I2C_State = 14; // Go to next state: generate Stop break; case 10: // Receive Data Ack/Nack bit USICTL0 &= ~USIOE; // SDA = input USICNT |= 0x01; // Bit counter = 1, receive (N)Ack bit I2C_State = 12; // Go to next state: check (N)Ack break; case 12: // Process Data Ack/Nack & send Stop USICTL0 |= USIOE; if (Bytecount == number_of_bytes){// If last byte USISRL = 0x00; I2C_State = 14; // Go to next state: generate Stop P1OUT |= 0x01; USICNT |= 0x01; } // set count=1 to trigger next state else{ P1OUT &= ~0x01; // Turn off LED Data_TX(); // TX byte } break; case 14:// Generate Stop Condition USISRL = 0x0FF; // USISRL = 1 to release SDA USICTL0 |= USIGE; // Transparent latch enabled USICTL0 &= ~(USIGE+USIOE); // Latch/SDA output disabled I2C_State = 0; // Reset state machine for next xmt LPM0_EXIT; // Exit active for next transfer break; } USICTL1 &= ~USIIFG; // Clear pending flag}void Data_TX (void){ USISRL = MST_Data++; // Load data byte USICNT |= 0x08; // Bit counter = 8, start TX I2C_State = 10; // next state: receive data (N)Ack Bytecount++;}void Data_RX (void){ USICTL0 &= ~USIOE; // SDA = input –> redundant USICNT |= 0x08; // Bit counter = 8, RX data I2C_State = 6; // Next state: Test data and (N)Ack P1OUT &= ~0x01; // LED off }void Setup_USI_Master_TX (void){ _DINT(); Bytecount = 0; Transmit = 1; USICTL0 = USIPE6+USIPE7+USIMST+USISWRST; // Port & USI mode setup USICTL1 = USII2C+USIIE; // Enable I2C mode & USI interrupt USICKCTL = USIDIV_7+USISSEL_2+USICKPL; // USI clk: SCL = SMCLK/128 USICNT |= USIIFGCC; // Disable automatic clear control USICTL0 &= ~USISWRST; // Enable USI USICTL1 &= ~USIIFG; // Clear pending flag _EINT();}void Setup_USI_Master_RX (void){ _DINT(); Bytecount = 0; Transmit = 0; USICTL0 = USIPE6+USIPE7+USIMST+USISWRST; // Port & USI mode setup USICTL1 = USII2C+USIIE; // Enable I2C mode & USI interrupt USICKCTL = USIDIV_7+USISSEL_2+USICKPL; // USI clks: SCL = SMCLK/128 USICNT |= USIIFGCC; // Disable automatic clear control USICTL0 &= ~USISWRST; // Enable USI USICTL1 &= ~USIIFG; // Clear pending flag _EINT();}void Master_Transmit(void){Setup_USI_Master_TX(); USICTL1 |= USIIFG; // Set flag and start communication LPM0; // CPU off, await USI interrupt __delay_cycles(10000); // Delay between comm cycles}void Master_Recieve(void){ Setup_USI_Master_RX(); USICTL1 |= USIIFG; // Set flag and start communication LPM0; // CPU off, await USI interrupt __delay_cycles(10000); // Delay between comm cycles}
Hardy Hu：
USI可以实现IIC接口，但是USI模块较简洁，实现IIC时要注意时序。
