MSP430G2553 Launchpad 硬件I2C驱动

  1 // msp430G2553 i2c bus <-> Si7021 humidity & temperature sensor
  2 // pullup resistors for SDA & SCL lines: 10kOhm
  3 // jumper for LED2 should be removed, or I2C bus won‘t work.
  4 
  5 #include "io430.h"
  6 #include "TI_USCI_I2C_master.h"
  7 
  8 #define SI7021_ADDRESS 0x40
  9 #define MEASURE_RH_HOLD 0xE5
 10 #define MEASURE_RH_NO_HOLD 0xF5
 11 #define READ_T_FROM_PRE_RH_MEASUREMENT 0xE0
 12 
 13 #define RXD BIT1 //P1.1
 14 #define TXD BIT2 //P1.2
 15 
 16 unsigned char array[1] = {0};
 17 unsigned char store[3] = {0, 0, 0};
 18 unsigned int outHumi = 0;
 19 float valueHumi = 0.0;
 20 int outTemp = 0;
 21 float valueTemp = 0.0;
 22 
 23 // functions for printf()
 24 void sendByte(unsigned char);
 25 void printf(char *, ...);
 26 void initUART(void);
 27 void printf_f(float);
 28 
 29 void main( void )
 30 {
 31     // Stop watchdog timer to prevent time out reset
 32     WDTCTL = WDTPW + WDTHOLD;
 33     
 34     // DCO setup
 35     BCSCTL1 = CALBC1_1MHZ;
 36     DCOCTL = CALDCO_1MHZ;
 37     
 38     // UART setup
 39     initUART();
 40     
 41     __enable_interrupt();
 42     
 43     while(1)
 44     {
 45         TI_USCI_I2C_transmitinit(SI7021_ADDRESS, 10); // init transmitting with USCI 
 46         // scl clock: f(BRCLK)/10; BRCLK <- SMCLK
 47         while(TI_USCI_I2C_notready()); // wait for bus to be free
 48         
 49         array[0] = MEASURE_RH_NO_HOLD;
 50         TI_USCI_I2C_transmit(1, array);
 51         while(TI_USCI_I2C_notready());
 52         
 53         __delay_cycles(25000); //delay 25ms
 54         
 55         // get the humidity result
 56         TI_USCI_I2C_receiveinit(SI7021_ADDRESS, 10);
 57         while(TI_USCI_I2C_notready());
 58         
 59         TI_USCI_I2C_receive(3,store);
 60         while(TI_USCI_I2C_notready()); 
 61         
 62         outHumi = (store[0]<<8) | store[1];
 63         valueHumi = 125.0*outHumi/65536 - 6;
 64         
 65         //printf("heX            %x\r\n", outHumi);
 66         //printf("heX            %x\r\n", (unsigned int)store[2]);
 67         //printf("Integer        %i\r\n", (int)valueHumi);
 68         printf_f(valueHumi);
 69         printf(" %%RH   ");
 70         
 71         
 72         // get temperature from previous RH measurement
 73         TI_USCI_I2C_transmitinit(SI7021_ADDRESS, 10); 
 74         while(TI_USCI_I2C_notready()); 
 75         array[0] = READ_T_FROM_PRE_RH_MEASUREMENT;
 76         TI_USCI_I2C_transmit(1, array);
 77         while(TI_USCI_I2C_notready());
 78         
 79         TI_USCI_I2C_receiveinit(SI7021_ADDRESS, 10); // init receiving with USCI 
 80         while(TI_USCI_I2C_notready()); // wait for bus to be free
 81         TI_USCI_I2C_receive(2,store);
 82         while(TI_USCI_I2C_notready()); 
 83         
 84         outTemp = (store[0]<<8) | store[1];
 85         valueTemp = 175.72*outTemp/65536 - 46.85;     
 86         
 87         //printf("heX            %x\r\n", outTemp);
 88         //printf("Integer        %i\r\n", (int)valueTemp);
 89         printf_f(valueTemp);
 90         printf(" `C\r\n");
 91         
 92         __delay_cycles(2000000); //delay 2s
 93     }
 94 }
 95 
 96 void initUART(void) {  
 97     //config P1.1 RXD, P1.2 TXD
 98     P1SEL |= TXD + RXD;
 99     P1SEL2 |= TXD + RXD;
100         
101     //reset UCA0, to be configured
102     UCA0CTL1 = UCSWRST;
103     //config
104     UCA0CTL1 |= UCSSEL_2; //SMCLK
105     UCA0BR0 = 104;
106     UCA0BR1 = 0;//1MHz baut rate = 9600
107     UCA0MCTL = UCBRS0; // Modulation UCBRSx = 1
108     //make UCA0 out of reset
109     UCA0CTL1 &= ~UCSWRST;
110 }
111 
112 void sendByte(unsigned char byte )
113 {
114     while (!(IFG2&UCA0TXIFG));            // USCI_A0 TX buffer ready?
115     UCA0TXBUF = byte;                // TX -> RXed character
116 }
117 
118 void printf_f(float fnumber)
119 {
120     int ipart = (int)fnumber; // integer part
121     int fpart = (int)((fnumber - ipart)*100); //fractional part, 2 decimal places
122     
123     printf("%i.", ipart);
124     
125     if(fpart<0)
126     {
127         fpart = -fpart;
128     }
129     if(fpart<10)
130     {
131         printf("0");
132     }
133     printf("%i", fpart);
134 }