原创 对SHT1x的驱动实现(二)

// sht1x_transstart
// generates a transmission start
//           ___     ___
// SCK : ___|   |___|   |______
//       _____         ________
// DATA:      |_______|
void sht1x_transstart(void)
{ 
        IO0CLR = SENSIBUS_DATA_OUT_PIN;                 // data=1
        IO0SET = SENSIBUS_SCK_PIN;                      // sck=0
        delay_mcu(32);                                  // 4us
        IO0CLR = SENSIBUS_SCK_PIN;                      // sck=1
        delay_mcu(32);                                  // 4us
        IO0SET = SENSIBUS_DATA_OUT_PIN;                 // data=0
        IO0SET = SENSIBUS_SCK_PIN;                      // sck=0       
        delay_mcu(64);                                  // 8us
        IO0CLR = SENSIBUS_SCK_PIN;                      // sck=1
        delay_mcu(32);                                  // 4us
        IO0CLR = SENSIBUS_DATA_OUT_PIN;                 // data=1       
        delay_mcu(32);                                  // 4us
        IO0SET = SENSIBUS_SCK_PIN;                      // sck=0
        delay_mcu(32);                                  // 4us
}

// communication reset: DATA-line=1 and at least 9 SCK cycles followed by transstart
//       _____________________________________________________         ________
// DATA:                                                      |_______|
//          _    _    _    _    _    _    _    _    _        ___     ___
// SCK : __| |__| |__| |__| |__| |__| |__| |__| |__| |______|   |___|   |______
void sht1x_connectionreset(void)
{ 
        IO0CLR = SENSIBUS_DATA_OUT_PIN;                 // data=1
        IO0SET = SENSIBUS_SCK_PIN;                      // sck=0
        delay_mcu(64);                                  // 8us
        for(U32 i=0; i<9; i++)                          // 9 SCK cycles
        {
            IO0CLR = SENSIBUS_SCK_PIN;                  // sck=1
            delay_mcu(32);                              // 2us
            IO0SET = SENSIBUS_SCK_PIN;                  // sck=0
            delay_mcu(32);                              // 2us
        }
        sht1x_transstart();                             //transmission start
}

// sht1x init: sensibus is two-wire machine: sck/data, now we apply 3 wire: sck/data_out/data_in for our system
void sht1x_init(void)
{
        // init io sck/data_out pin as output
        IO0DIR |= SENSIBUS_SCK_PIN; 
        IO0DIR |= SENSIBUS_DATA_OUT_PIN;
        // init io data_in pin as input
        IO0DIR = IO0DIR & (~(SENSIBUS_DATA_IN_PIN));  
}

/*
 * sht1x_measure
 *
 * Description:
 *      Measure temperature and relative rumidity with blocking loop delay, it is about 300ms for 14bit temperature(from our experiment), and
 *      about 100ms for 12 bit relative humidity(from datasheet). The measure process include checksum.
 *
 * Parameter:
 *      p_value:    the address of 16bit unsigned int(U16)
 *      checksum:   checksum byte from sensi-sensor
 *      mode:       0; temprature;  1: relative humidity;  
 *
 * History:
 *      2010/08/29: Init design.
 */
U8 sht1x_measure(U8 *p_value, U8 *p_checksum, U8 mode)
{
        U32 i = 0;
        U8 error = 0;

        // do convert      
        error = sht1x_do_convert(mode);
       
        //wait until sensor has finished the measurement with 2s timeout
        for(i=0; i<20; i++) {
            delay_ms(100);
            watchdog_soft_hard_feed();
            if( (IO0PIN&SENSIBUS_DATA_IN_PIN) != 0x00 ) { break; }  // if data==0
        }
        // test measure time
        //uart0_putnum(i, 10);

        // read result
        error = sht1x_read_result(p_value, p_checksum);

        return error;
}

// sht1x_do_temperature_convert
U8 sht1x_do_convert(U8 mode)
{
        U8 error = 0;

        //transmission start
        sht1x_connectionreset();
       
        //send command to sensor
        switch(mode){                    
           
        case 0:
            error += sht1x_write_byte(MEASURE_TEMP);
            break;
        case 1:
            error += sht1x_write_byte(MEASURE_HUMI);
            break;
        default:
          break; 
        }

        return error;       
}

// sht1x_read_result
U8 sht1x_read_result(U8 *p_value, U8 *p_checksum)
{
        U8 error = 0;

        // read result
        if( (IO0PIN&SENSIBUS_DATA_IN_PIN) == 0x00 )     // if data==1
            error += 1;
        *(p_value+1) = sht1x_read_byte(ACK);
        *(p_value) = sht1x_read_byte(ACK);
        *p_checksum  = sht1x_read_byte(noACK);

        return error; 
}

Allen
2010.09.05 于深圳上沙创新科技园


对SHT1x的驱动实现(一)
对SHT1x的驱动实现(二)