DS28E01-100_drv_C.zip_DS28E01_ds28e01-100_hardhcm

//This souce file includes the basic one wire operation functions: delayow, write bit, read bit, write byte, read byte; //resetpresense, CRC8 check, CRC16 check. //This functions are called by other routines. //#include "SYS.H" #include "PORT.H" #include "c8051f020.h" #include <absacc.h> sbit DQ = P1^2; //The following is the function prototypes void delayow(uint16); void writebit(uint8); uint8 readbit(); void writebyte(uint8); uint8 readbyte(); uint8 restpresnese(); //The following is the function body //Delay function, the unit delay is about 10uS void delayow(uint16 us) { uint16 idata i; for (i = 0; i <= us; i++) { } } //Resetpresense function uint8 rest() { uint8 idata pre; DQ = 0; //DQ is the ow data/power line defined in sys.h. delayow(500); //Delay for the reset pulse. DQ = 1; //Release the line so that the slave can drive the line low after a while. delayow(60); //Delay for the slave to drive the line low. pre = (uint8)DQ; delayow(480); //Delay for the slave to release the line. DQ = 1; //Host drive the line high. return pre; } //Write bit void writebit(uint8 sendbit) { DQ = 0; delayow(2); //Delay for the leading signal. if (sendbit == 0x01) { //If the send bit is 1 then release the line. DQ = 1; } delayow(80); //Delay for the 1 wire device to sample the line. DQ = 1; //Release the line to be in idle state. delayow(10); //Delay for recovery time. return; } //Read bit uint8 readbit() { uint8 idata readbit; DQ = 0; delayow(2); //Delay for the leading signal. DQ = 1; //Host "release" the line. delayow(10); //Delay for the data put on the line by slave to be stable. readbit = (uint8)DQ; delayow(70); //delayoe for the slave to release the line, including the recoery time. DQ = 1; //Host "forces" the line to be in idle state. return readbit; } //Write byte void writebyte(uint8 senddata) { uint8 idata i; uint8 idata temp; for (i = 0x00; i <= 0x07; i++) { temp = senddata >> i; //The data to be send is right shifted to the right most position of the byte according to the real position writebit(temp & 0x01); //of the data, and the data is "and" with 0x01, to determine if the send data is 0 or 1. } } //Read byte uint8 Readbyte() { uint8 idata readdata = 0x00; //The readdata is initialised to 0x00. uint16 idata setcontrol = 0x0001; //The setcontrol is initialised to 0x0001,and will be shifted left when each time reading a bit. while (setcontrol <= 0x0080) { //Why using uint16 instead of uint8?If use uint8, what will happen after left shifting 0x80? It depends on if (readbit()) { //machine implementation.So for portable purpose we use uint16. readdata = readdata | setcontrol;//If the read bit is 1 then readdata is "or" with setcontrol and store back to readdata. } setcontrol = setcontrol << 1; //Left shift the setcontrol. } return readdata; }