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/////////////////////////////////////////////////////////////////////////////// |
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/////////////////////////////////////////////////////////////////////////////// |
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// // |
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// // |
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// Driver file for SHT75 Temperature & Humidity Sensor // |
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// Driver file for SHT1x Temperature & Humidity Sensor // |
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// // |
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// // |
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// ***** To initialise SHT75 sensor upon power up ***** // |
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// ***** To initialise SHT1x sensor upon power up ***** // |
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// // |
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// // |
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// Function : sht_init() // |
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// Function : sht_init() // |
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// Return : none // |
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// Return : none // |
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// // |
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// // |
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// // |
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// // |
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// ***** To measure and caluculate SHT75 temp & real RH ***** // |
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// ***** To measure and caluculate SHT75 temp & real RH ***** // |
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// // |
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// // |
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// Function : sht_rd (temp, truehumid) // |
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// Function : sht_rd (temp, truehumid) // |
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// Return : temperature & true humidity in float values // |
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// Return : temperature & true humidity in float values // |
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// // |
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// // |
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/////////////////////////////////////////////////////////////////////////////// |
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/////////////////////////////////////////////////////////////////////////////// |
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|
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|
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//#define sht_data_pin PIN_D0 |
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//#define sht_data_pin PIN_D0 |
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//#define sht_clk_pin PIN_D1 |
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//#define sht_clk_pin PIN_D1 |
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|
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|
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|
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|
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//***** Function to alert SHT75 ***** |
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//***** Function to alert SHT75 ***** |
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|
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// generates a transmission start |
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|
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// _____ ________ |
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|
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// DATA: |_______| |
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|
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// ___ ___ |
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|
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// SCK : ___| |___| |______ |
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|
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|
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void comstart (void) |
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void sht_comstart (void) |
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{ |
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{ |
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output_float(sht_data_pin); //data high |
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output_float(sht_data_pin); //data high |
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output_low(sht_clk_pin); //clk low |
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output_low(sht_clk_pin); //clk low |
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delay_us(2); |
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delay_us(2); |
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output_high(sht_clk_pin); //clk high |
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output_high(sht_clk_pin); //clk high |
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delay_us(2); |
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delay_us(2); |
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output_low(sht_data_pin); //data low |
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output_low(sht_data_pin); //data low |
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delay_us(2); |
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delay_us(2); |
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output_low(sht_clk_pin); //clk low |
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output_low(sht_clk_pin); //clk low |
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delay_us(5); |
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delay_us(5); |
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output_high(sht_clk_pin); //clk high |
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output_high(sht_clk_pin); //clk high |
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delay_us(2); |
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delay_us(2); |
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output_float(sht_data_pin); //data high |
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output_float(sht_data_pin); //data high |
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delay_us(2); |
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delay_us(2); |
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output_low(sht_clk_pin); //clk low |
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output_low(sht_clk_pin); //clk low |
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} |
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} |
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|
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|
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|
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|
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//***** Function to write data to SHT75 ***** |
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//***** Function to write data to SHT75 ***** |
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|
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|
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int1 comwrite (int8 iobyte) |
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int1 sht_comwrite (int8 iobyte) |
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{ |
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{ |
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int8 i, mask = 0x80; |
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int8 i, mask = 0x80; |
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int1 ack; |
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int1 ack; |
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|
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|
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//Shift out command |
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//Shift out command |
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delay_us(5); |
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delay_us(5); |
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for(i=0; i<8; i++) |
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for(i=0; i<8; i++) |
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{ |
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{ |
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output_low(sht_clk_pin); //clk low |
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output_low(sht_clk_pin); //clk low |
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if((iobyte & mask) > 0) output_float(sht_data_pin); //data high if MSB high |
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if((iobyte & mask) > 0) output_float(sht_data_pin); //data high if MSB high |
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else output_low(sht_data_pin); //data low if MSB low |
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else output_low(sht_data_pin); //data low if MSB low |
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delay_us(2); |
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delay_us(2); |
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output_high(sht_clk_pin); //clk high |
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output_high(sht_clk_pin); //clk high |
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delay_us(2); |
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delay_us(2); |
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mask = mask >> 1; //shift to next bit |
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mask = mask >> 1; //shift to next bit |
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} |
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} |
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|
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|
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//Shift in ack |
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//Shift in ack |
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output_low(sht_clk_pin); //clk low |
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output_low(sht_clk_pin); //clk low |
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delay_us(2); |
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delay_us(2); |
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ack = input(sht_data_pin); //get ack bit |
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ack = input(sht_data_pin); //get ack bit |
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output_high(sht_clk_pin); //clk high |
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output_high(sht_clk_pin); //clk high |
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delay_us(2); |
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delay_us(2); |
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output_low(sht_clk_pin); //clk low |
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output_low(sht_clk_pin); //clk low |
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return(ack); |
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return(ack); |
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} |
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} |
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|
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|
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|
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|
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//***** Function to read data from SHT75 ***** |
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//***** Function to read data from SHT75 ***** |
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|
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|
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int16 comread (void) |
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int16 sht_comread (void) |
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{ |
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{ |
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int8 i; |
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int8 i; |
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int16 iobyte = 0; |
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int16 iobyte = 0; |
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const int16 mask0 = 0x0000; |
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const int16 mask0 = 0x0000; |
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const int16 mask1 = 0x0001; |
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const int16 mask1 = 0x0001; |
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|
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|
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//shift in MSB data |
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//shift in MSB data |
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for(i=0; i<8; i++) |
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for(i=0; i<8; i++) |
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{ |
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{ |
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iobyte = iobyte << 1; |
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iobyte = iobyte << 1; |
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output_high(sht_clk_pin); //clk high |
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output_high(sht_clk_pin); //clk high |
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delay_us(2); |
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delay_us(2); |
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if (input(sht_data_pin)) iobyte |= mask1; //shift in data bit |
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if (input(sht_data_pin)) iobyte |= mask1; //shift in data bit |
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else iobyte |= mask0; |
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else iobyte |= mask0; |
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output_low(sht_clk_pin); //clk low |
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output_low(sht_clk_pin); //clk low |
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delay_us(2); |
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delay_us(2); |
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} |
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} |
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|
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|
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//send ack 0 bit |
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//send ack 0 bit |
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output_low(sht_data_pin); //data low |
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output_low(sht_data_pin); //data low |
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delay_us(2); |
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delay_us(2); |
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output_high(sht_clk_pin); //clk high |
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output_high(sht_clk_pin); //clk high |
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delay_us(5); |
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delay_us(5); |
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output_low(sht_clk_pin); //clk low |
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output_low(sht_clk_pin); //clk low |
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delay_us(2); |
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delay_us(2); |
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output_float(sht_data_pin); //data high |
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output_float(sht_data_pin); //data high |
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|
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|
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//shift in LSB data |
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//shift in LSB data |
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for(i=0; i<8; i++) |
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for(i=0; i<8; i++) |
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{ |
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{ |
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iobyte = iobyte << 1; |
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iobyte = iobyte << 1; |
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output_high(sht_clk_pin); //clk high |
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output_high(sht_clk_pin); //clk high |
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delay_us(2); |
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delay_us(2); |
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if (input(sht_data_pin)) iobyte |= mask1; //shift in data bit |
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if (input(sht_data_pin)) iobyte |= mask1; //shift in data bit |
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else iobyte |= mask0; |
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else iobyte |= mask0; |
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output_low(sht_clk_pin); //clk low |
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output_low(sht_clk_pin); //clk low |
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delay_us(2); |
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delay_us(2); |
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} |
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} |
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|
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|
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//send ack 1 bit |
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//send ack 1 bit |
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output_float(sht_data_pin); //data high |
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output_float(sht_data_pin); //data high |
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delay_us(2); |
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delay_us(2); |
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output_high(sht_clk_pin); //clk high |
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output_high(sht_clk_pin); //clk high |
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delay_us(5); |
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delay_us(5); |
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output_low(sht_clk_pin); //clk low |
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output_low(sht_clk_pin); //clk low |
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|
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|
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return(iobyte); |
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return(iobyte); |
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} |
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} |
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|
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|
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|
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|
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//***** Function to wait for SHT75 reading ***** |
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//***** Function to wait for SHT75 reading ***** |
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|
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|
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void comwait (void) |
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void sht_comwait (void) |
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{ |
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{ |
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int16 sht_delay; |
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int16 sht_delay; |
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|
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|
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output_float(sht_data_pin); //data high |
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output_float(sht_data_pin); //data high |
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output_low(sht_clk_pin); //clk low |
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output_low(sht_clk_pin); //clk low |
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delay_us(2); |
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delay_us(2); |
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for(sht_delay=0; sht_delay<30000; sht_delay++) // wait for max 300ms |
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for(sht_delay=0; sht_delay<350; sht_delay++) // wait for max 350ms (for 14bit measurement) |
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{ |
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{ |
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if (!input(sht_data_pin)) break; //if sht_data_pin low, SHT75 ready |
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if (!input(sht_data_pin)) break; //if sht_data_pin low, SHT75 ready |
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delay_us(10); |
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delay_ms(1); |
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} |
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} |
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} |
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} |
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|
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|
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|
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|
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//***** Function to reset SHT75 communication ***** |
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//***** Function to reset SHT75 communication ***** |
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|
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|
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|
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// communication reset: DATA-line=1 and at least 9 SCK cycles followed by transstart |
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|
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// _____________________________________________________ ________ |
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|
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// DATA: |_______| |
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|
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// _ _ _ _ _ _ _ _ _ ___ ___ |
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|
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// SCK : __| |__| |__| |__| |__| |__| |__| |__| |__| |______| |___| |______ |
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void comreset (void) |
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void sht_comreset (void) |
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{ |
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{ |
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int8 i; |
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int8 i; |
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|
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|
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output_float(sht_data_pin); //data high |
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output_float(sht_data_pin); //data high |
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output_low(sht_clk_pin); //clk low |
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output_low(sht_clk_pin); //clk low |
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delay_us(5); |
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delay_us(5); |
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for(i=0; i<9; i++) |
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for(i=0; i<9; i++) |
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{ |
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{ |
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output_high(sht_clk_pin); //toggle clk 9 times |
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output_high(sht_clk_pin); //toggle clk 9 times |
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delay_us(5); |
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delay_us(5); |
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output_low(sht_clk_pin); |
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output_low(sht_clk_pin); |
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delay_us(5); |
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delay_us(5); |
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} |
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} |
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comstart(); |
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sht_comstart(); |
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} |
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} |
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|
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|
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|
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|
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//***** Function to soft reset SHT75 ***** |
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//***** Function to soft reset SHT75 ***** |
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|
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|
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void sht_soft_reset (void) |
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void sht_soft_reset (void) |
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{ |
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{ |
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comreset(); //SHT75 communication reset |
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sht_comreset(); //SHT75 communication reset |
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comwrite(0x1e); //send SHT75 reset command |
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sht_comwrite(0x1e); //send SHT75 reset command |
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delay_ms(15); //pause 15 ms |
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delay_ms(15); //pause 15 ms |
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} |
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} |
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|
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|
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|
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|
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//***** Function to measure SHT75 temperature ***** |
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//***** Function to measure SHT75 temperature ***** |
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|
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|
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int16 measuretemp (void) |
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int16 sht_measuretemp (void) |
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{ |
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{ |
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int1 ack; |
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int1 ack; |
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int16 iobyte; |
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int16 iobyte; |
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|
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|
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comstart(); //alert SHT75 |
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sht_comstart(); //alert SHT75 |
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ack = comwrite(0x03); //send measure temp command and read ack status |
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ack = sht_comwrite(0x03); //send measure temp command and read ack status |
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if(ack == 1) return; |
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if(ack == 1) return; |
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comwait(); //wait for SHT75 measurement to complete |
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sht_comwait(); //wait for SHT75 measurement to complete |
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iobyte = comread(); //read SHT75 temp data |
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iobyte = sht_comread(); //read SHT75 temp data |
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return(iobyte); |
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return(iobyte); |
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} |
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} |
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|
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|
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|
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|
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//***** Function to measure SHT75 RH ***** |
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//***** Function to measure SHT75 RH ***** |
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|
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|
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int16 measurehumid (void) |
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int16 sht_measurehumid (void) |
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{ |
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{ |
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int1 ack; |
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int1 ack; |
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int16 iobyte; |
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int16 iobyte; |
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|
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|
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comstart(); //alert SHT75 |
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sht_comstart(); //alert SHT75 |
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ack = comwrite(0x05); //send measure RH command and read ack status |
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ack = sht_comwrite(0x05); //send measure RH command and read ack status |
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if(ack == 1) return; |
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if(ack == 1) return; |
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comwait(); //wait for SHT75 measurement to complete |
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sht_comwait(); //wait for SHT75 measurement to complete |
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iobyte = comread(); //read SHT75 temp data |
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iobyte = sht_comread(); //read SHT75 temp data |
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return(iobyte); |
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return(iobyte); |
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} |
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} |
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|
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|
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|
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|
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//***** Function to calculate SHT75 temp & RH ***** |
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//***** Function to calculate SHT75 temp & RH ***** |
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|
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|
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void calculate_data (int16 temp, int16 humid, float & tc, float & rhlin, float & rhtrue) |
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void calculate_data (int16 temp, int16 humid, float & tc, float & rhlin, float & rhtrue) |
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{ |
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{ |
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float truehumid1, rh; |
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float rh; |
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|
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|
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//calculate temperature reading |
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//calculate temperature reading |
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tc = ((float) temp * 0.01) - 40.0; |
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tc = ((float) temp * 0.01) - 40.0; |
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|
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|
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//calculate Real RH reading |
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//calculate Real RH reading |
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rh = (float) humid; |
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rh = (float) humid; |
217 |
|
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|
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rhlin = (rh * 0.0405) - (rh * rh * 0.0000028) - 4.0; |
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rhlin = (rh * 0.0405) - (rh * rh * 0.0000028) - 4.0; |
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|
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|
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//calculate True RH reading |
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//calculate True RH reading |
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rhtrue = ((tc - 25.0) * (0.01 + (0.00008 * rh))) + rhlin; |
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rhtrue = ((tc - 25.0) * (0.01 + (0.00008 * rh))) + rhlin; |
222 |
} |
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} |
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|
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|
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|
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|
225 |
//***** Function to measure & calculate SHT75 temp & RH ***** |
234 |
//***** Function to measure & calculate SHT75 temp & RH ***** |
226 |
|
235 |
|
227 |
void sht_rd (float & temp, float & truehumid) |
236 |
void sht_rd (float & temp, float & truehumid) |
228 |
{ |
237 |
{ |
229 |
int16 restemp, reshumid; |
238 |
int16 restemp, reshumid; |
230 |
float realhumid; |
239 |
float realhumid; |
231 |
restemp = 0; truehumid = 0; |
240 |
restemp = 0; truehumid = 0; |
232 |
|
241 |
|
233 |
restemp = measuretemp(); //measure temp |
242 |
restemp = sht_measuretemp(); //measure temp |
234 |
reshumid = measurehumid(); //measure RH |
243 |
reshumid = sht_measurehumid(); //measure RH |
235 |
calculate_data (restemp, reshumid, temp, realhumid, truehumid); //calculate temp & RH |
244 |
calculate_data (restemp, reshumid, temp, realhumid, truehumid); //calculate temp & RH |
236 |
} |
245 |
} |
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|
246 |
|
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|
247 |
|
239 |
//***** Function to initialise SHT75 on power-up ***** |
248 |
//***** Function to initialise SHT75 on power-up ***** |
240 |
|
249 |
|
241 |
void sht_init (void) |
250 |
void sht_init (void) |
242 |
{ |
251 |
{ |
243 |
comreset(); //reset SHT75 |
252 |
sht_comreset(); //reset SHT75 |
244 |
delay_ms(20); //delay for power-up |
253 |
delay_ms(20); //delay for power-up |
245 |
} |
254 |
} |