esp-open-rtos/extras/onewire/onewire.c

#include "onewire.h"
#include "string.h"
#include "task.h"
#include "esp/gpio.h"

// 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 false;
//
// Returns true if a device asserted a presence pulse, false otherwise.
//
bool onewire_reset(int pin) {
    bool r;
    const int retries = 50;

    gpio_enable(pin, GPIO_OUT_OPEN_DRAIN);
    gpio_write(pin, 1);
    // wait until the wire is high... just in case
    for (int i = 0; i < retries; i++) {
        if (gpio_read(pin)) break;
        sdk_os_delay_us(5);
    }
    if (!gpio_read(pin)) {
        // Bus shorted?
        return false;
    }

    gpio_write(pin, 0);
    sdk_os_delay_us(480);

    taskENTER_CRITICAL();
    gpio_write(pin, 1); // allow it to float
    sdk_os_delay_us(70);
    r = !gpio_read(pin);
    taskEXIT_CRITICAL();

    // Wait for all devices to finish pulling the bus low before returning
    for (int i = 0; i < retries; i++) {
        if (gpio_read(pin)) break;
        sdk_os_delay_us(5);
    }
    sdk_os_delay_us(2);

    return r;
}

static void onewire_write_bit(int pin, uint8_t v) {
    //TODO: should verify that the bus is high before starting
    if (v & 1) {
        taskENTER_CRITICAL();
        gpio_write(pin, 0);  // drive output low
        sdk_os_delay_us(10);
        gpio_write(pin, 1);  // allow output high
        taskEXIT_CRITICAL();
        sdk_os_delay_us(55);
    } else {
        taskENTER_CRITICAL();
        gpio_write(pin, 0);  // drive output low
        sdk_os_delay_us(65);
        gpio_write(pin, 1); // allow output high
        taskEXIT_CRITICAL();
    }
    sdk_os_delay_us(1);
}

static int onewire_read_bit(int pin) {
    int r;

    //TODO: should verify that the bus is high before starting
    taskENTER_CRITICAL();
    gpio_write(pin, 0);
    sdk_os_delay_us(2);
    gpio_write(pin, 1);  // let pin float, pull up will raise
    sdk_os_delay_us(11);
    r = gpio_read(pin);  // Must sample within 15us of start
    taskEXIT_CRITICAL();
    sdk_os_delay_us(48);

    return r;
}

// Write a byte. The writing code uses open-drain mode and expects the pullup
// resistor to pull the line high when not driven low.  If you need strong
// power after the write (e.g. DS18B20 in parasite power mode) then call
// onewire_power() after this is complete to actively drive the line high.
//
void onewire_write(int pin, uint8_t v) {
    uint8_t bitMask;

    for (bitMask = 0x01; bitMask; bitMask <<= 1) {
        onewire_write_bit(pin, (bitMask & v)?1:0);
    }
}

void onewire_write_bytes(int pin, const uint8_t *buf, size_t count) {
    size_t i;

    for (i = 0 ; i < count ; i++) {
        onewire_write(pin, buf[i]);
    }
}

// Read a byte
//
uint8_t onewire_read(int 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(int pin, uint8_t *buf, size_t count) {
    size_t i;

    for (i = 0 ; i < count ; i++) {
        buf[i] = onewire_read(pin);
    }
}

// Do a ROM select
//
void onewire_select(int pin, onewire_addr_t rom) {
    uint8_t i;

    onewire_write(pin, 0x55);  // Choose ROM

    for (i = 0; i < 8; i++) {
        onewire_write(pin, rom & 0xff);
        rom >>= 8;
    }
}

// Do a ROM skip
//
void onewire_skip_rom(int pin) {
    onewire_write(pin, 0xCC);  // Skip ROM
}

void onewire_power(int pin) {
    gpio_enable(pin, GPIO_OUTPUT);
    gpio_write(pin, 1);
}

void onewire_depower(int pin) {
    gpio_enable(pin, GPIO_OUT_OPEN_DRAIN);
}

void onewire_search_start(onewire_search_t *search) {
    // reset the search state
    memset(search, 0, sizeof(*search));
}

// Setup the search to find the device type 'family_code' on the next call
// to search(*newAddr) if it is present.
//
void onewire_search_prefix(onewire_search_t *search, uint8_t family_code) {
    uint8_t i;

    search->rom_no[0] = family_code;
    for (i = 1; i < 8; i++) {
        search->rom_no[i] = 0;
    }
    search->last_discrepancy = 64;
    search->last_device_found = false;
}

// Perform a search. If the next device has been successfully enumerated, its
// ROM address will be returned.  If there are no devices, no further
// devices, or something horrible happens in the middle of the
// enumeration then ONEWIRE_NONE is returned.  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
//
onewire_addr_t onewire_search_next(onewire_search_t *search, int pin) {
    uint8_t id_bit_number;
    uint8_t last_zero, search_result;
    int rom_byte_number;
    uint8_t id_bit, cmp_id_bit;
    onewire_addr_t addr;

    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 (!search->last_device_found) {
        // 1-Wire reset
        if (!onewire_reset(pin)) {
            // reset the search
            search->last_discrepancy = 0;
            search->last_device_found = false;
            return ONEWIRE_NONE;
        }

        // issue the search command
        onewire_write(pin, 0xF0);

        // 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 < search->last_discrepancy) {
                        search_direction = ((search->rom_no[rom_byte_number] & rom_byte_mask) > 0);
                    } else {
                        // if equal to last pick 1, if not then pick 0
                        search_direction = (id_bit_number == search->last_discrepancy);
                    }

                    // if 0 was picked then record its position in LastZero
                    if (search_direction == 0) {
                        last_zero = id_bit_number;
                    }
                }

                // set or clear the bit in the ROM byte rom_byte_number
                // with mask rom_byte_mask
                if (search_direction == 1) {
                    search->rom_no[rom_byte_number] |= rom_byte_mask;
                } else {
                    search->rom_no[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 last_discrepancy,last_device_found,search_result
            search->last_discrepancy = last_zero;

            // check for last device
            if (search->last_discrepancy == 0) {
                search->last_device_found = true;
            }

            search_result = 1;
        }
    }

    // if no device found then reset counters so next 'search' will be like a first
    if (!search_result || !search->rom_no[0]) {
        search->last_discrepancy = 0;
        search->last_device_found = false;
        return ONEWIRE_NONE;
    } else {
        addr = 0;
        for (rom_byte_number = 7; rom_byte_number >= 0; rom_byte_number--) {
            addr = (addr << 8) | search->rom_no[rom_byte_number];
        }
        //printf("Ok I found something at %08x%08x...\n", (uint32_t)(addr >> 32), (uint32_t)addr);
    }
    return addr;
}

// 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 *data, uint8_t len) {
    uint8_t crc = 0;

    while (len--) {
        crc = pgm_read_byte(dscrc_table + (crc ^ *data++));
    }
    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 *data, uint8_t len) {
    uint8_t crc = 0;
    
    while (len--) {
        uint8_t inbyte = *data++;
        for (int 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, size_t len, const uint8_t* inverted_crc, uint16_t crc_iv) {
    uint16_t crc = ~onewire_crc16(input, len, crc_iv);
    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, size_t len, uint16_t crc_iv) {
    uint16_t crc = crc_iv;
    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;
}