An experimental timer interrupt driven software based 1-Wire master interface that was created by Robert David Brinzer for a University of Glasgow Level 4 Electronic and Software Engineering Final Year project. This implementation requires mbed RTOS and does not use NOP waits. Perfect for programs that require multi-tasking. Includes the Read and Search network commands and can be easily extended to support new network and transport commands.
Instructions/Transport.cpp
- Committer:
- sroy
- Date:
- 2013-04-15
- Revision:
- 0:7c6dd6bc20e4
File content as of revision 0:7c6dd6bc20e4:
#include "Transport.h" /* This table helps with the compution of the CRC8 used in OneWire ROM * * The theory is that it precomputes all possible states that an eight bit shift register * can go to from a certain state when given a certain byte. Computationally and array * lookup should be considerably faster than simulating the shift register a bit at a time. * * Table was sourced from maxim document AN937 that describes the standard. */ const unsigned char crc8table[256] = { 0, 94, 188, 226, 97, 63, 221, 131, 194, 156, 126, 32, 163, 253, 31, 65, 157, 195, 33, 127, 252, 162, 64, 30, 95, 1, 227, 189, 62, 96, 130, 220, 35, 125, 159, 193, 66, 28, 254, 160, 225, 191, 93, 3, 128, 222, 60, 98, 190, 224, 2, 92, 223, 129, 99, 61, 124, 34, 192, 158, 29, 67, 161, 255, 70, 24, 250, 164, 39, 121, 155, 197, 132, 218, 56, 102, 229, 187, 89, 7, 219, 133, 103, 57, 186, 228, 6, 88, 25, 71, 165, 251, 120, 38, 196, 154, 101, 59, 217, 135, 4, 90, 184, 230, 167, 249, 27, 69, 198, 152, 122, 36, 248, 166, 68, 26, 153, 199, 37, 123, 58, 100, 134, 216, 91, 5, 231, 185, 140, 210, 48, 110, 237, 179, 81, 15, 78, 16, 242, 172, 47, 113, 147, 205, 17, 79, 173, 243, 112, 46, 204, 146, 211, 141, 111, 49, 178, 236, 14, 80, 175, 241, 19, 77, 206, 144, 114, 44, 109, 51, 209, 143, 12, 82, 176, 238, 50, 108, 142, 208, 83, 13, 239, 177, 240, 174, 76, 18, 145, 207, 45, 115, 202, 148, 118, 40, 171, 245, 23, 73, 8, 86, 180, 234, 105, 55, 213, 139, 87, 9, 235, 181, 54, 104, 138, 212, 149, 203, 41, 119, 244, 170, 72, 22, 233, 183, 85, 11, 136, 214, 52, 106, 43, 117, 151, 201, 74, 20, 246, 168, 116, 42, 200, 150, 21, 75, 169, 247, 182, 232, 10, 84, 215, 137, 107, 53}; // read command void OWTransport::read(OneWire_Instruction * inst, OneWire_ROM * out){ inst->network.code = READ_ROM; inst->network.inst = &OWTransport::_inst_readsetup; inst->network.args = out; *out = 0; // clear rom to a valid value (0 does pass CRC8 but is impossible to get as a device) } void OWTransport::_inst_readsetup(OneWire * which){ // setup register ((TransportRead *)(which->registers))->read = 0; ((TransportRead *)(which->registers))->crc8 = 0; // setup command which->readhandle = &OWTransport::_inst_readhandler; which->execute.inst = &OWTransport::_inst_read; // execute command OWTransport::_inst_read(which); } void OWTransport::_inst_read(OneWire * which){ if(((TransportRead *)(which->registers))->read < 64){ which->op_read(); }else{ // check if crc8 check passed (remainder 0), failure is not recoverable if(((TransportRead *)(which->registers))->crc8) which->abort(CRC_ERROR); else which->endInstruction(); } } void OWTransport::_inst_readhandler(OneWire * which, char bit){ // store bit *((unsigned char *)(which->execute.args))|= bit<<(((TransportRead *)(which->registers))->read++%8); // every 8 bits (byte) compute CRC8 and move to next byte if(!(((TransportRead *)(which->registers))->read % 8)){ ((TransportRead *)(which->registers))->crc8 = crc8table[((TransportRead *)(which->registers))->crc8 ^ (*((unsigned char *)(which->execute.args)))]; which->execute.args = (void *)(((unsigned char *)(which->execute.args))+1); } } // search command void TransportSearchPersist::clear(){ rom = 0; last = -1; done = false; } void OWTransport::search(OneWire_Instruction * inst, TransportSearchPersist * search){ inst->network.code = SEARCH_ROM; inst->network.inst = &OWTransport::_inst_searchsetup; inst->network.args = search; } void OWTransport::_inst_searchsetup(OneWire * which){ if(((TransportSearchPersist *)(which->execute.args))->done){ // the search had completed, there is nothing more to do which->abort(SUCCESS); return; } // setup register ((TransportSearch *)(which->registers))->read = 0; ((TransportSearch *)(which->registers))->crc8 = 0; ((TransportSearch *)(which->registers))->marker = -1; ((TransportSearch *)(which->registers))->bit = 0; // setup command which->readhandle = &OWTransport::_inst_searchhandler; which->execute.inst = &OWTransport::_inst_search; // execute command OWTransport::_inst_search(which); } void OWTransport::_inst_search(OneWire * which){ if(((TransportSearch *)(which->registers))->read < 64){ // state machine, read bit 1 -> read bit 2 and make choice -> send choice -> repeat up to 64 times if(((TransportSearch *)(which->registers))->bit>>3 & 0x01){ // send choosen bit and advance if(((unsigned char *)&(((TransportSearchPersist *)(which->execute.args))->rom))[((TransportSearch *)(which->registers))->read/8]>>(((TransportSearch *)(which->registers))->read%8) &0x01){ which->op_send1(); }else{ which->op_send0(); } // compute crc8 if(((TransportSearch *)(which->registers))->read % 8 == 7){ ((TransportSearch *)(which->registers))->crc8 = crc8table[((TransportSearch *)(which->registers))->crc8 ^ ((unsigned char *)&(((TransportSearchPersist *)(which->execute.args))->rom))[((TransportSearch *)(which->registers))->read/8]]; } // prepare for next cycle (reset state machine) ((TransportSearch *)(which->registers))->read+= 1; ((TransportSearch *)(which->registers))->bit = 0; }else{ // read bit 1 and 2 (read function advances state machine) which->op_read(); } }else{ ((TransportSearchPersist *)(which->execute.args))->last = ((TransportSearch *)(which->registers))->marker; if(((TransportSearchPersist *)(which->execute.args))->last == -1) ((TransportSearchPersist *)(which->execute.args))->done = true; // check if crc8 check passed (remainder 0), failure is not recoverable if(((TransportSearch *)(which->registers))->crc8) which->abort(CRC_ERROR); else which->endInstruction(); } } void OWTransport::_inst_searchhandler(OneWire * which, char bit){ // store bit ((TransportSearch *)(which->registers))->bit|= bit<<(((TransportSearch *)(which->registers))->bit>>2 & 0x01); // advance state if(((TransportSearch *)(which->registers))->bit>>2 & 0x01){ if((((TransportSearch *)(which->registers))->bit & 0x03) == 3){ // all slaves were removed or broke? ((TransportSearchPersist *)(which->execute.args))->done = true; // any search results that were obtained could be invalid so end search which->abort(NO_PRESENCE); return; }else if((((TransportSearch *)(which->registers))->bit & 0x03) == 0){ // a conflict bit if(((TransportSearch *)(which->registers))->read == ((TransportSearchPersist *)(which->execute.args))->last){ // already searched 0 bit path, this time send a 1 ((unsigned char *)&(((TransportSearchPersist *)(which->execute.args))->rom))[((TransportSearch *)(which->registers))->read/8]|= 0x01<<(((TransportSearch *)(which->registers))->read%8); }else if(((TransportSearch *)(which->registers))->read > ((TransportSearchPersist *)(which->execute.args))->last){ // a new branch to search ((unsigned char *)&(((TransportSearchPersist *)(which->execute.args))->rom))[((TransportSearch *)(which->registers))->read/8]&= ~(0x01<<(((TransportSearch *)(which->registers))->read%8)); ((TransportSearch *)(which->registers))->marker = ((TransportSearch *)(which->registers))->read; }else if( !(((unsigned char *)&(((TransportSearchPersist *)(which->execute.args))->rom))[((TransportSearch *)(which->registers))->read/8]>>(((TransportSearch *)(which->registers))->read%8) &0x01) ){ // a previous branch decision ((TransportSearch *)(which->registers))->marker = ((TransportSearch *)(which->registers))->read; } }else{ // no conflict so write the bit if(((TransportSearch *)(which->registers))->bit & 0x01){ ((unsigned char *)&(((TransportSearchPersist *)(which->execute.args))->rom))[((TransportSearch *)(which->registers))->read/8]|= 0x01<<(((TransportSearch *)(which->registers))->read%8); }else{ ((unsigned char *)&(((TransportSearchPersist *)(which->execute.args))->rom))[((TransportSearch *)(which->registers))->read/8]&= ~(0x01<<(((TransportSearch *)(which->registers))->read%8)); } } // tell next call to send the choice ((TransportSearch *)(which->registers))->bit|= 0x08; }else{ // we need to read another bit ((TransportSearch *)(which->registers))->bit|= 0x04; } }