static uint8_t config_calc_checksum(void) { uint8_t crc = 0; crc = calc_crc8(crc, &task, sizeof task); crc = calc_crc8(crc, &zone, sizeof zone); crc = calc_crc8(crc, &brightness, sizeof brightness); crc = calc_crc8(crc, &action, sizeof action); return crc; }
//-------------------------------------------------------------------------- // The 'OWSearch' function does a general search. This function // continues from the previous search state. The search state // can be reset by using the 'OWFirst' function. // This function contains one parameter 'alarm_only'. // When 'alarm_only' is TRUE (1) the find alarm command // 0xEC is sent instead of the normal search command 0xF0. // Using the find alarm command 0xEC will limit the search to only // 1-Wire devices that are in an 'alarm' state. // // Returns: TRUE (1) : when a 1-Wire device was found and its // Serial Number placed in the global ROM // FALSE (0): when no new device was found. Either the // last search was the last device or there // are no devices on the 1-Wire Net. // int OWSearch() { int id_bit_number; int last_zero, rom_byte_number, search_result; int id_bit, cmp_id_bit; unsigned char rom_byte_mask, search_direction, status; // initialize for search id_bit_number = 1; last_zero = 0; rom_byte_number = 0; rom_byte_mask = 1; search_result = FALSE; crc8 = 0; // if the last call was not the last one if (!LastDeviceFlag) { // 1-Wire reset if (!OWReset()) { // reset the search LastDiscrepancy = 0; LastDeviceFlag = FALSE; LastFamilyDiscrepancy = 0; return FALSE; } // issue the search command OWWriteByte(0xF0); // loop to do the search do { // if this discrepancy if before the Last Discrepancy // on a previous next then pick the same as last time if (id_bit_number < LastDiscrepancy) { if ((ROM_NO[rom_byte_number] & rom_byte_mask) > 0) search_direction = 1; else search_direction = 0; } else { // if equal to last pick 1, if not then pick 0 if (id_bit_number == LastDiscrepancy) search_direction = 1; else search_direction = 0; } // Perform a triple operation on the DS2482 which will perform 2 read bits and 1 write bit status = DS2482_search_triplet(search_direction); // check bit results in status byte id_bit = ((status & DS2482_STATUS_SBR) == DS2482_STATUS_SBR); cmp_id_bit = ((status & DS2482_STATUS_TSB) == DS2482_STATUS_TSB); search_direction = ((status & DS2482_STATUS_DIR) == DS2482_STATUS_DIR) ? 0x01 : 0x00; // check for no devices on 1-Wire if ((id_bit) && (cmp_id_bit)) break; else { if ((!id_bit) && (!cmp_id_bit) && (search_direction == 0)) { last_zero = id_bit_number; // check for Last discrepancy in family if (last_zero < 9) LastFamilyDiscrepancy = 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[rom_byte_number] |= rom_byte_mask; else ROM_NO[rom_byte_number] &= (uint8_t)~rom_byte_mask; // 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) { calc_crc8(ROM_NO[rom_byte_number]); // accumulate the CRC rom_byte_number++; rom_byte_mask = 1; } } } while(rom_byte_number < 8); // (do-while) loop until through all ROM bytes 0-7 // if the search was successful then if (!((id_bit_number < 65) || (crc8 != 0))) { // search successful so set LastDiscrepancy,LastDeviceFlag,search_result LastDiscrepancy = last_zero; // check for last device if (LastDiscrepancy == 0) LastDeviceFlag = TRUE; search_result = TRUE; } } // if no device found then reset counters so next 'search' will be like a first if (!search_result || (ROM_NO[0] == 0)) { LastDiscrepancy = 0; LastDeviceFlag = FALSE; LastFamilyDiscrepancy = 0; search_result = FALSE; } return search_result; }