Scott Roy / OneWire

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@0:7c6dd6bc20e4, 2013-04-15 (annotated)

Committer:
sroy
Date:
Mon Apr 15 07:02:49 2013 +0000
Revision:
0:7c6dd6bc20e4
An experimental 1-Wire Master interface driven by timer interrupts rather than NOP waits created as part of a University of Glasgow Level 4 Electronic and Software Engineering final year project.   Requires the use of mbed RTOS.

Who changed what in which revision?

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