３．４．20_プログラムリスト(SHT75.c)/////////////////////////////////////////////////////////////////////////////// // // Driver file for SHT75 Temperature & Humidity Sensor // // ***** To initialise SHT75 sensor upon power up ***** // // Function : sht_init() // Return : none // // // ***** To measure and caluculate SHT75 temp & real RH ***** // // Function : sht_rd (temp, truehumid) // Return : temperature & true humidity in float value // /////////////////////////////////////////////////////////////////////////////// #define sht_data_pin PIN_A1 #define sht_clk_pin PIN_A0 //***** Function to alert SHT75 ***** void comstart (void) { output_float(sht_data_pin); //data high output_bit(sht_clk_pin, 0); //clk low delay_us(1); output_bit(sht_clk_pin, 1); //clk high delay_us(1); output_bit(sht_data_pin, 0); //data low delay_us(1); output_bit(sht_clk_pin, 0); //clk low delay_us(2); output_bit(sht_clk_pin, 1); //clk high delay_us(1); output_float(sht_data_pin); //data high delay_us(1); output_bit(sht_clk_pin, 0); //clk low } //***** Function to write data to SHT75 ***** int1 comwrite (int8 iobyte) { int8 i, mask = 0x80; int1 ack; //Shift out command delay_us(4); for(i=0; i<8; i++) { output_bit(sht_clk_pin, 0); //clk low if((iobyte & mask) > 0) output_float(sht_data_pin); //data high if MSB high else output_bit(sht_data_pin, 0); //data low if MSB low delay_us(1); output_bit(sht_clk_pin, 1); //clk high delay_us(1); mask = mask >> 1; //shift to next bit } //Shift in ack output_bit(sht_clk_pin, 0); //clk low delay_us(1); ack = input(sht_data_pin); //get ack bit output_bit(sht_clk_pin, 1); //clk high delay_us(1); output_bit(sht_clk_pin, 0); //clk low return(ack); } //***** Function to read data from SHT75 ***** int16 comread (void) { int8 i; int16 iobyte = 0; const int16 mask0 = 0x0000; const int16 mask1 = 0x0001; //shift in MSB data for(i=0; i<8; i++) { iobyte = iobyte << 1; output_bit(sht_clk_pin, 1); //clk high delay_us(1); if (input(sht_data_pin)) iobyte |= mask1; //shift in data bit else iobyte |= mask0; output_bit(sht_clk_pin, 0); //clk low delay_us(1); } //send ack 0 bit output_bit(sht_data_pin, 0); //data low delay_us(1); output_bit(sht_clk_pin, 1); //clk high delay_us(2); output_bit(sht_clk_pin, 0); //clk low delay_us(1); output_float(sht_data_pin); //data high //shift in LSB data for(i=0; i<8; i++) { iobyte = iobyte << 1; output_bit(sht_clk_pin, 1); //clk high delay_us(1); if (input(sht_data_pin)) iobyte |= mask1; //shift in data bit else iobyte |= mask0; output_bit(sht_clk_pin, 0); //clk low delay_us(1); } //send ack 1 bit output_float(sht_data_pin); //data high delay_us(1); output_bit(sht_clk_pin, 1); //clk high delay_us(2); output_bit(sht_clk_pin, 0); //clk low return(iobyte); } //***** Function to wait for SHT75 reading ***** void comwait (void) { int16 sht_delay; output_float(sht_data_pin); //data high output_bit(sht_clk_pin, 0); //clk low delay_us(1); for(sht_delay=0; sht_delay<30000; sht_delay++) // wait for max 300ms { if (!input(sht_data_pin)) break; //if sht_data_pin low, SHT75 ready delay_us(10); } } //***** Function to reset SHT75 communication ***** void comreset (void) { int8 i; output_float(sht_data_pin); //data high output_bit(sht_clk_pin, 0); //clk low delay_us(2); for(i=0; i<9; i++) { output_bit(sht_clk_pin, 1); //toggle clk 9 times delay_us(2); output_bit(sht_clk_pin, 0); delay_us(2); } comstart(); } //***** Function to soft reset SHT75 ***** void sht_soft_reset (void) { comreset(); //SHT75 communication reset comwrite(0x1e); //send SHT75 reset command delay_ms(15); //pause 15 ms } //***** Function to measure SHT75 temperature ***** int16 measuretemp (void) { int1 ack; int16 iobyte; comstart(); //alert SHT75 ack = comwrite(0x03); //send measure temp command and read ack status if(ack == 1) return; comwait(); //wait for SHT75 measurement to complete iobyte = comread(); //read SHT75 temp data return(iobyte); } //***** Function to measure SHT75 RH ***** int16 measurehumid (void) { int1 ack; int16 iobyte; comstart(); //alert SHT75 ack = comwrite(0x05); //send measure RH command and read ack status if(ack == 1) return; comwait(); //wait for SHT75 measurement to complete iobyte = comread(); //read SHT75 temp data return(iobyte); } //***** Function to calculate SHT75 temp & RH ***** void calculate_data (int16 temp, int16 humid, float & tc, float & rhlin, float & rhtrue) { float rh; //calculate temperature reading tc = ((float) temp * 0.01) - 40.0; //calculate Real RH reading rh = (float) humid; rhlin = (rh * 0.0405) - (rh * rh * 0.0000028) - 4.0; //calculate True RH reading rhtrue = ((tc - 25.0) * (0.01 + (0.00008 * rh))) + rhlin; } //***** Function to measure & calculate SHT75 temp & RH ***** void sht_rd (float & temp, float & truehumid) { int16 restemp, reshumid; float realhumid; restemp = 0; truehumid = 0; restemp = measuretemp(); //measure temp reshumid = measurehumid(); //measure RH calculate_data (restemp, reshumid, temp, realhumid, truehumid); //calculate temp & RH } //***** Function to initialise SHT75 on power-up ***** void sht_init (void) { comreset(); //reset SHT75 delay_ms(20); //delay for power-up } トップページヘもどる |