Onewire.cpp

00001 #include "Onewire.h"
00002 
00003 Onewire::Onewire(PinName oneBus):oneBus_(oneBus){
00004 
00005 }
00006 void Onewire::writeBit(int bit) {
00007     bit = bit & 0x01;
00008     if (bit) {
00009         // Write '1' bit
00010         oneBus_.output();
00011         oneBus_ = 0;
00012         wait_us(5);
00013         oneBus_.input();
00014         wait_us(60);
00015     } else {
00016         // Write '0' bit
00017         oneBus_.output();
00018         oneBus_ = 0;
00019         wait_us(70);
00020         oneBus_.input();
00021         wait_us(2);
00022     }
00023 }
00024 
00025 int Onewire::readBit() {
00026     char result;
00027 
00028     oneBus_.output();
00029     oneBus_ = 0;
00030     wait_us(1);
00031     oneBus_.input();
00032     wait_us(5);
00033     result = oneBus_.read();
00034     wait_us(55);
00035     return result;
00036 
00037 }
00038 
00039 int Onewire::init() {
00040     oneBus_.output();
00041     oneBus_ = 0;
00042     wait_us(480);
00043     oneBus_.input();
00044     wait_us(60);
00045     if (oneBus_.read() == 0) {
00046         wait(0.0001);
00047         return 1;
00048     }
00049     return 0;
00050 }
00051 int Onewire::readByte() {
00052     int result = 0;
00053 
00054     for (int loop = 0; loop < 8; loop++) {
00055         // shift the result to get it ready for the next bit
00056         result >>= 1;
00057 
00058         // if result is one, then set MS bit
00059         if (readBit())
00060             result |= 0x80;
00061     }
00062     return result;
00063 }
00064 void Onewire::writeByte(char data) {
00065     // Loop to write each bit in the byte, LS-bit first
00066     for (int loop = 0; loop < 8; loop++) {
00067         writeBit(data & 0x01);
00068 
00069         // shift the data byte for the next bit
00070         data >>= 1;
00071     }
00072 }
00073 unsigned char Onewire::CRC(unsigned char* addr, unsigned char len) {
00074     unsigned char i, j;
00075     unsigned char crc = 0;
00076 
00077     for (i = 0; i < len; i++) {
00078         unsigned char inbyte = addr[i];
00079         for (j = 0; j < 8; j++) {
00080             unsigned char mix = (crc ^ inbyte) & 0x01;
00081             crc >>= 1;
00082             if (mix) crc ^= 0x8C;
00083             inbyte >>= 1;
00084         }
00085     }
00086 
00087     return crc;
00088 }
00089