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copied!<p>Here is some code that I wrote for a PIC18 to read a DS18B20.</p> <pre><code>/**************************************************************************** * temperature.h ****************************************************************************/ #ifndef TEMP_H #define TEMP_H extern double read_temp(void) ; extern void start_temp(void); #endif /**************************************************************************** * temperature.c ****************************************************************************/ void reset_ow(void); void write_ow(uint8_t b); uint8_t read_ow (void); #define OW_TEMP_SIG LATHbits.LATH0 #define OW_TEMP_TRIS TRISHbits.TRISH0 #define OW_TEMP_SIG_IN PORTHbits.RH0 #define DIR_OUT 0 #define DIR_IN 1 void start_temp(void) { uint8_t i; OW_TEMP_SIG=1; OW_TEMP_TRIS=DIR_OUT; for ( i=0;i<100;i++) { Delay_us(100); } reset_ow(); write_ow(0xcc); // skip rom write_ow(0x44); // start t conv } double read_temp(void) { double temp=0; S16 itemp; reset_ow(); write_ow(0xcc); // skip rom write_ow(0xbe); // read scratch pad itemp=read_ow(); itemp|=(S16)read_ow()<<8; temp = itemp*(0.0625); OW_TEMP_TRIS=DIR_IN; OW_TEMP_SIG=1; return temp; } void reset_ow(void) { OW_TEMP_TRIS=DIR_OUT; OW_TEMP_SIG=0; Delay_us(250); Delay_us(250); OW_TEMP_TRIS=DIR_IN; OW_TEMP_SIG=1; Delay_us(250); Delay_us(250); } void write_ow(uint8_t b) { uint8_t i; OW_TEMP_SIG=1; OW_TEMP_TRIS=DIR_OUT; for ( i=0;i<8;i++) { OW_TEMP_SIG=0; if ( b & 0x01 ) { Delay_us(10); OW_TEMP_SIG=1; } Delay_us(70); OW_TEMP_SIG=1; Delay_us(10); b >>= 1; } OW_TEMP_TRIS=DIR_IN; OW_TEMP_SIG=1; } uint8_t read_ow(void) { uint8_t b=0; uint8_t m; uint8_t i; m=1; for ( i=0;i<8;i++) { OW_TEMP_SIG=1; OW_TEMP_TRIS=DIR_OUT; OW_TEMP_SIG=0; Delay_us(8); OW_TEMP_TRIS=DIR_IN; OW_TEMP_SIG=1; Delay_us(15); if ( 1 == OW_TEMP_SIG_IN ) { b |= m; } m <<=1; Delay_us(60); } OW_TEMP_TRIS=DIR_IN; OW_TEMP_SIG=1; return b; } </code></pre>

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