#include "onewire.h"
// global search state
static unsigned char ROM_NO[ONEWIRE_NUM][8];
static uint8_t LastDiscrepancy[ONEWIRE_NUM];
static uint8_t LastFamilyDiscrepancy[ONEWIRE_NUM];
static uint8_t LastDeviceFlag[ONEWIRE_NUM];
void onewire_init(uint8_t pin)
{
gpio_enable(pin, GPIO_INPUT);
onewire_reset_search(pin);
}
// Perform the onewire reset function. We will wait up to 250uS for
// the bus to come high, if it doesn't then it is broken or shorted
// and we return a 0;
//
// Returns 1 if a device asserted a presence pulse, 0 otherwise.
//
uint8_t onewire_reset(uint8_t pin)
{
uint8_t r;
uint8_t retries = 125;
noInterrupts();
DIRECT_MODE_INPUT(pin);
interrupts();
// wait until the wire is high... just in case
do {
if (--retries == 0) return 0;
delayMicroseconds(2);
} while ( !DIRECT_READ(pin));
noInterrupts();
DIRECT_WRITE_LOW(pin);
DIRECT_MODE_OUTPUT(pin); // drive output low
interrupts();
delayMicroseconds(480);
noInterrupts();
DIRECT_MODE_INPUT(pin); // allow it to float
delayMicroseconds(70);
r = !DIRECT_READ(pin);
interrupts();
delayMicroseconds(410);
return r;
}
// Write a bit. Port and bit is used to cut lookup time and provide
// more certain timing.
//
static void onewire_write_bit(uint8_t pin, uint8_t v)
{
if (v & 1) {
noInterrupts();
DIRECT_WRITE_LOW(pin);
DIRECT_MODE_OUTPUT(pin); // drive output low
delayMicroseconds(10);
DIRECT_WRITE_HIGH(pin); // drive output high
interrupts();
delayMicroseconds(55);
} else {
noInterrupts();
DIRECT_WRITE_LOW(pin);
DIRECT_MODE_OUTPUT(pin); // drive output low
delayMicroseconds(65);
DIRECT_WRITE_HIGH(pin); // drive output high
interrupts();
delayMicroseconds(5);
}
}
// Read a bit. Port and bit is used to cut lookup time and provide
// more certain timing.
//
static uint8_t onewire_read_bit(uint8_t pin)
{
uint8_t r;
noInterrupts();
DIRECT_MODE_OUTPUT(pin);
DIRECT_WRITE_LOW(pin);
delayMicroseconds(3);
DIRECT_MODE_INPUT(pin); // let pin float, pull up will raise
delayMicroseconds(10);
r = DIRECT_READ(pin);
interrupts();
delayMicroseconds(53);
return r;
}
// Write a byte. The writing code uses the active drivers to raise the
// pin high, if you need power after the write (e.g. DS18S20 in
// parasite power mode) then set 'power' to 1, otherwise the pin will
// go tri-state at the end of the write to avoid heating in a short or
// other mishap.
//
void onewire_write(uint8_t pin, uint8_t v, uint8_t power /* = 0 */) {
uint8_t bitMask;
for (bitMask = 0x01; bitMask; bitMask <<= 1) {
onewire_write_bit(pin, (bitMask & v)?1:0);
}
if ( !power) {
noInterrupts();
DIRECT_MODE_INPUT(pin);
DIRECT_WRITE_LOW(pin);
interrupts();
}
}
void onewire_write_bytes(uint8_t pin, const uint8_t *buf, uint16_t count, bool power /* = 0 */) {
uint16_t i;
for (i = 0 ; i < count ; i++)
onewire_write(pin, buf[i], ONEWIRE_DEFAULT_POWER);
if (!power) {
noInterrupts();
DIRECT_MODE_INPUT(pin);
DIRECT_WRITE_LOW(pin);
interrupts();
}
}
// Read a byte
//
uint8_t onewire_read(uint8_t pin) {
uint8_t bitMask;
uint8_t r = 0;
for (bitMask = 0x01; bitMask; bitMask <<= 1) {
if (onewire_read_bit(pin)) r |= bitMask;
}
return r;
}
void onewire_read_bytes(uint8_t pin, uint8_t *buf, uint16_t count) {
uint16_t i;
for (i = 0 ; i < count ; i++)
buf[i] = onewire_read(pin);
}
// Do a ROM select
//
void onewire_select(uint8_t pin, const uint8_t rom[8])
{
uint8_t i;
onewire_write(pin, 0x55, ONEWIRE_DEFAULT_POWER); // Choose ROM
for (i = 0; i < 8; i++) onewire_write(pin, rom[i], ONEWIRE_DEFAULT_POWER);
}
// Do a ROM skip
//
void onewire_skip(uint8_t pin)
{
onewire_write(pin, 0xCC, ONEWIRE_DEFAULT_POWER); // Skip ROM
}
void onewire_depower(uint8_t pin)
{
noInterrupts();
DIRECT_MODE_INPUT(pin);
interrupts();
}
// You need to use this function to start a search again from the beginning.
// You do not need to do it for the first search, though you could.
//
void onewire_reset_search(uint8_t pin)
{
// reset the search state
LastDiscrepancy[pin] = 0;
LastDeviceFlag[pin] = 0;
LastFamilyDiscrepancy[pin] = 0;
int i;
for(i = 7; ; i--) {
ROM_NO[pin][i] = 0;
if ( i == 0) break;
}
}
// Setup the search to find the device type 'family_code' on the next call
// to search(*newAddr) if it is present.
//
void onewire_target_search(uint8_t pin, uint8_t family_code)
{
// set the search state to find SearchFamily type devices
ROM_NO[pin][0] = family_code;
uint8_t i;
for (i = 1; i < 8; i++)
ROM_NO[pin][i] = 0;
LastDiscrepancy[pin] = 64;
LastFamilyDiscrepancy[pin] = 0;
LastDeviceFlag[pin] = 0;
}
// Perform a search. If this function returns a '1' then it has
// enumerated the next device and you may retrieve the ROM from the
// OneWire::address variable. If there are no devices, no further
// devices, or something horrible happens in the middle of the
// enumeration then a 0 is returned. If a new device is found then
// its address is copied to newAddr. Use OneWire::reset_search() to
// start over.
//
// --- Replaced by the one from the Dallas Semiconductor web site ---
//--------------------------------------------------------------------------
// Perform the 1-Wire Search Algorithm on the 1-Wire bus using the existing
// search state.
// Return 1 : device found, ROM number in ROM_NO buffer
// 0 : device not found, end of search
//
uint8_t onewire_search(uint8_t pin, uint8_t *newAddr)
{
uint8_t id_bit_number;
uint8_t last_zero, rom_byte_number, search_result;
uint8_t id_bit, cmp_id_bit;
unsigned char rom_byte_mask, search_direction;
// initialize for search
id_bit_number = 1;
last_zero = 0;
rom_byte_number = 0;
rom_byte_mask = 1;
search_result = 0;
// if the last call was not the last one
if (!LastDeviceFlag[pin])
{
// 1-Wire reset
if (!onewire_reset(pin))
{
// reset the search
LastDiscrepancy[pin] = 0;
LastDeviceFlag[pin] = 0;
LastFamilyDiscrepancy[pin] = 0;
return 0;
}
// issue the search command
onewire_write(pin, 0xF0, ONEWIRE_DEFAULT_POWER);
// loop to do the search
do
{
// read a bit and its complement
id_bit = onewire_read_bit(pin);
cmp_id_bit = onewire_read_bit(pin);
// check for no devices on 1-wire
if ((id_bit == 1) && (cmp_id_bit == 1))
break;
else
{
// all devices coupled have 0 or 1
if (id_bit != cmp_id_bit)
search_direction = id_bit; // bit write value for search
else
{
// if this discrepancy if before the Last Discrepancy
// on a previous next then pick the same as last time
if (id_bit_number < LastDiscrepancy[pin])
search_direction = ((ROM_NO[pin][rom_byte_number] & rom_byte_mask) > 0);
else
// if equal to last pick 1, if not then pick 0
search_direction = (id_bit_number == LastDiscrepancy[pin]);
// if 0 was picked then record its position in LastZero
if (search_direction == 0)
{
last_zero = id_bit_number;
// check for Last discrepancy in family
if (last_zero < 9)
LastFamilyDiscrepancy[pin] = last_zero;
}
}
// set or clear the bit in the ROM byte rom_byte_number
// with mask rom_byte_mask
if (search_direction == 1)
ROM_NO[pin][rom_byte_number] |= rom_byte_mask;
else
ROM_NO[pin][rom_byte_number] &= ~rom_byte_mask;
// serial number search direction write bit
onewire_write_bit(pin, search_direction);
// increment the byte counter id_bit_number
// and shift the mask rom_byte_mask
id_bit_number++;
rom_byte_mask <<= 1;
// if the mask is 0 then go to new SerialNum byte rom_byte_number and reset mask
if (rom_byte_mask == 0)
{
rom_byte_number++;
rom_byte_mask = 1;
}
}
}
while(rom_byte_number < 8); // loop until through all ROM bytes 0-7
// if the search was successful then
if (!(id_bit_number < 65))
{
// search successful so set LastDiscrepancy,LastDeviceFlag,search_result
LastDiscrepancy[pin] = last_zero;
// check for last device
if (LastDiscrepancy[pin] == 0)
LastDeviceFlag[pin] = 1;
search_result = 1;
}
}
// if no device found then reset counters so next 'search' will be like a first
if (!search_result || !ROM_NO[pin][0])
{
LastDiscrepancy[pin] = 0;
LastDeviceFlag[pin] = 0;
LastFamilyDiscrepancy[pin] = 0;
search_result = 0;
}
else
{
for (rom_byte_number = 0; rom_byte_number < 8; rom_byte_number++)
{
newAddr[rom_byte_number] = ROM_NO[pin][rom_byte_number];
//printf("Ok I found something at %d - %x...\n",rom_byte_number, newAddr[rom_byte_number]);
}
}
return search_result;
}
// The 1-Wire CRC scheme is described in Maxim Application Note 27:
// "Understanding and Using Cyclic Redundancy Checks with Maxim iButton Products"
//
#if ONEWIRE_CRC8_TABLE
// This table comes from Dallas sample code where it is freely reusable,
// though Copyright (C) 2000 Dallas Semiconductor Corporation
static const uint8_t dscrc_table[] = {
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};
#ifndef pgm_read_byte
#define pgm_read_byte(addr) (*(const uint8_t *)(addr))
#endif
//
// Compute a Dallas Semiconductor 8 bit CRC. These show up in the ROM
// and the registers. (note: this might better be done without to
// table, it would probably be smaller and certainly fast enough
// compared to all those delayMicrosecond() calls. But I got
// confused, so I use this table from the examples.)
//
uint8_t onewire_crc8(const uint8_t *addr, uint8_t len)
{
uint8_t crc = 0;
while (len--) {
crc = pgm_read_byte(dscrc_table + (crc ^ *addr++));
}
return crc;
}
#else
//
// Compute a Dallas Semiconductor 8 bit CRC directly.
// this is much slower, but much smaller, than the lookup table.
//
uint8_t onewire_crc8(const uint8_t *addr, uint8_t len)
{
uint8_t crc = 0;
while (len--) {
uint8_t inbyte = *addr++;
uint8_t i;
for (i = 8; i; i--) {
uint8_t mix = (crc ^ inbyte) & 0x01;
crc >>= 1;
if (mix) crc ^= 0x8C;
inbyte >>= 1;
}
}
return crc;
}
#endif
// Compute the 1-Wire CRC16 and compare it against the received CRC.
// Example usage (reading a DS2408):
// // Put everything in a buffer so we can compute the CRC easily.
// uint8_t buf[13];
// buf[0] = 0xF0; // Read PIO Registers
// buf[1] = 0x88; // LSB address
// buf[2] = 0x00; // MSB address
// WriteBytes(net, buf, 3); // Write 3 cmd bytes
// ReadBytes(net, buf+3, 10); // Read 6 data bytes, 2 0xFF, 2 CRC16
// if (!CheckCRC16(buf, 11, &buf[11])) {
// // Handle error.
// }
//
// @param input - Array of bytes to checksum.
// @param len - How many bytes to use.
// @param inverted_crc - The two CRC16 bytes in the received data.
// This should just point into the received data,
// *not* at a 16-bit integer.
// @param crc - The crc starting value (optional)
// @return 1, iff the CRC matches.
bool onewire_check_crc16(const uint8_t* input, uint16_t len, const uint8_t* inverted_crc, uint16_t crc)
{
crc = ~onewire_crc16(input, len, crc);
return (crc & 0xFF) == inverted_crc[0] && (crc >> 8) == inverted_crc[1];
}
// Compute a Dallas Semiconductor 16 bit CRC. This is required to check
// the integrity of data received from many 1-Wire devices. Note that the
// CRC computed here is *not* what you'll get from the 1-Wire network,
// for two reasons:
// 1) The CRC is transmitted bitwise inverted.
// 2) Depending on the endian-ness of your processor, the binary
// representation of the two-byte return value may have a different
// byte order than the two bytes you get from 1-Wire.
// @param input - Array of bytes to checksum.
// @param len - How many bytes to use.
// @param crc - The crc starting value (optional)
// @return The CRC16, as defined by Dallas Semiconductor.
uint16_t onewire_crc16(const uint8_t* input, uint16_t len, uint16_t crc)
{
static const uint8_t oddparity[16] =
{ 0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0 };
uint16_t i;
for (i = 0 ; i < len ; i++) {
// Even though we're just copying a byte from the input,
// we'll be doing 16-bit computation with it.
uint16_t cdata = input[i];
cdata = (cdata ^ crc) & 0xff;
crc >>= 8;
if (oddparity[cdata & 0x0F] ^ oddparity[cdata >> 4])
crc ^= 0xC001;
cdata <<= 6;
crc ^= cdata;
cdata <<= 1;
crc ^= cdata;
}
return crc;
}