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DS18B20 integer version
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‎docs/lua-modules/ds18b20.md‎

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This Lua module provides access to [DS18B20](https://datasheets.maximintegrated.com/en/ds/DS18B20.pdf) 1-Wire digital thermometer.
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!!! note
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The module requires `ow` C module built into firmware.
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For integer version of firmware use [ds18b20-integer.lua](../../lua_modules/ds18b20/ds18b20-integer.lua) module - measured temperatures are multiplied by 10000.
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The module requires `ow` C module built into firmware.
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### Require
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```lua

‎lua_modules/ds18b20/ds18b20-integer.lua‎

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--------------------------------------------------------------------------------
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-- DS18B20 one wire module for NODEMCU
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-- NODEMCU TEAM
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-- LICENCE: http://opensource.org/licenses/MIT
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-- @voborsky, @devsaurus, TerryE 26 Mar 2017
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--------------------------------------------------------------------------------
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local modname = ...
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-- Used modules and functions
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local type, tostring, pcall, ipairs =
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type, tostring, pcall, ipairs
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-- Local functions
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local ow_setup, ow_search, ow_select, ow_read, ow_read_bytes, ow_write, ow_crc8,
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ow_reset, ow_reset_search, ow_skip, ow_depower =
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ow.setup, ow.search, ow.select, ow.read, ow.read_bytes, ow.write, ow.crc8,
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ow.reset, ow.reset_search, ow.skip, ow.depower
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local node_task_post, node_task_LOW_PRIORITY = node.task.post, node.task.LOW_PRIORITY
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local string_char, string_dump = string.char, string.dump
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local now, tmr_create, tmr_ALARM_SINGLE = tmr.now, tmr.create, tmr.ALARM_SINGLE
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local table_sort, table_concat = table.sort, table.concat
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local math_floor = math.floor
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local file_open = file.open
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local conversion
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local DS18B20FAMILY = 0x28
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local DS1920FAMILY = 0x10 -- and DS18S20 series
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local CONVERT_T = 0x44
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local READ_SCRATCHPAD = 0xBE
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local READ_POWERSUPPLY= 0xB4
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local MODE = 1
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local pin, cb, unit = 3
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local status = {}
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local debugPrint = function() return end
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--------------------------------------------------------------------------------
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-- Implementation
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--------------------------------------------------------------------------------
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local function enable_debug()
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debugPrint = function (...) print(now(),' ', ...) end
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end
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local function to_string(addr, esc)
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if type(addr) == 'string' and #addr == 8 then
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return ( esc == true and
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'"\\%u\\%u\\%u\\%u\\%u\\%u\\%u\\%u"' or
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'%02X:%02X:%02X:%02X:%02X:%02X:%02X:%02X '):format(addr:byte(1,8))
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else
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return tostring(addr)
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end
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end
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local function readout(self)
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local next = false
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local sens = self.sens
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local temp = self.temp
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for i, s in ipairs(sens) do
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if status[i] == 1 then
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ow_reset(pin)
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local addr = s:sub(1,8)
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ow_select(pin, addr) -- select the sensor
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ow_write(pin, READ_SCRATCHPAD, MODE)
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local data = ow_read_bytes(pin, 9)
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local t=(data:byte(1)+data:byte(2)*256)
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-- t is actually signed so process the sign bit and adjust for fractional bits
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-- the DS18B20 family has 4 fractional bits and the DS18S20s, 1 fractional bit
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t = ((t <= 32767) and t or t - 65536) *
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((addr:byte(1) == DS18B20FAMILY) and 625 or 5000)
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local crc, b9 = ow_crc8(string.sub(data,1,8)), data:byte(9)
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if unit == 'F' then
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t = (t * 18)/10 + 320000
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elseif unit == 'K' then
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t = t + 2731500
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end
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local sgn = t<0 and -1 or 1
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local tA = sgn*t
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local tH=tA/10000
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local tL=(tA%10000)/1000 + ((tA%1000)/100 >= 5 and 1 or 0)
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if tH and (t~=850000) then
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debugPrint(to_string(addr),(sgn<0 and "-" or "")..tH.."."..tL, crc, b9)
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if crc==b9 then temp[addr]=t end
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status[i] = 2
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end
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end
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next = next or status[i] == 0
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end
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if next then
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node_task_post(node_task_LOW_PRIORITY, function() return conversion(self) end)
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else
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--sens = {}
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if cb then
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node_task_post(node_task_LOW_PRIORITY, function() return cb(temp) end)
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end
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end
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end
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conversion = (function (self)
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local sens = self.sens
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local powered_only = true
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for _, s in ipairs(sens) do powered_only = powered_only and s:byte(9) ~= 1 end
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if powered_only then
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debugPrint("starting conversion: all sensors")
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ow_reset(pin)
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ow_skip(pin) -- skip ROM selection, talk to all sensors
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ow_write(pin, CONVERT_T, MODE) -- and start conversion
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for i, _ in ipairs(sens) do status[i] = 1 end
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else
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local started = false
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for i, s in ipairs(sens) do
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if status[i] == 0 then
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local addr, parasite = s:sub(1,8), s:byte(9) == 1
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if parasite and started then break end -- do not start concurrent conversion of powered and parasite
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debugPrint("starting conversion:", to_string(addr), parasite and "parasite" or "")
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ow_reset(pin)
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ow_select(pin, addr) -- select the sensor
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ow_write(pin, CONVERT_T, MODE) -- and start conversion
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status[i] = 1
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if parasite then break end -- parasite sensor blocks bus during conversion
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started = true
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end
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end
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end
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tmr_create():alarm(750, tmr_ALARM_SINGLE, function() return readout(self) end)
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end)
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local function _search(self, lcb, lpin, search, save)
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self.temp = {}
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if search then self.sens = {}; status = {} end
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local sens = self.sens
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pin = lpin or pin
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local addr
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if not search and #sens == 0 then
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-- load addreses if available
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debugPrint ("geting addreses from flash")
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local s,check,a = pcall(dofile, "ds18b20_save.lc")
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if s and check == "ds18b20" then
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for i = 1, #a do sens[i] = a[i] end
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end
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debugPrint (#sens, "addreses found")
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end
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ow_setup(pin)
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if search or #sens == 0 then
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ow_reset_search(pin)
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-- ow_target_search(pin,0x28)
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-- search the first device
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addr = ow_search(pin)
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else
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for i, _ in ipairs(sens) do status[i] = 0 end
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end
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local function cycle()
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if addr then
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local crc=ow_crc8(addr:sub(1,7))
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if (crc==addr:byte(8)) and ((addr:byte(1)==DS1920FAMILY) or (addr:byte(1)==DS18B20FAMILY)) then
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ow_reset(pin)
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ow_select(pin, addr)
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ow_write(pin, READ_POWERSUPPLY, MODE)
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local parasite = (ow_read(pin)==0 and 1 or 0)
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sens[#sens+1]= addr..string_char(parasite)
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status[#sens] = 0
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debugPrint("contact: ", to_string(addr), parasite == 1 and "parasite" or "")
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end
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addr = ow_search(pin)
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node_task_post(node_task_LOW_PRIORITY, cycle)
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else
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ow_depower(pin)
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-- place powered sensors first
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table_sort(sens, function(a, b) return a:byte(9)<b:byte(9) end) -- parasite
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-- save sensor addreses
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if save then
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debugPrint ("saving addreses to flash")
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local addr_list = {}
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for i =1, #sens do
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local s = sens[i]
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addr_list[i] = to_string(s:sub(1,8), true)..('.."\\%u"'):format(s:byte(9))
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end
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local save_statement = 'return "ds18b20", {' .. table_concat(addr_list, ',') .. '}'
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debugPrint (save_statement)
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local save_file = file_open("ds18b20_save.lc","w")
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save_file:write(string_dump(loadstring(save_statement)))
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save_file:close()
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end
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-- end save sensor addreses
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if lcb then node_task_post(node_task_LOW_PRIORITY, lcb) end
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end
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end
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cycle()
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end
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local function read_temp(self, lcb, lpin, lunit, force_search, save_search)
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cb, unit = lcb, lunit or unit
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_search(self, function() return conversion(self) end, lpin, force_search, save_search)
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end
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-- Set module name as parameter of require and return module table
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local M = {
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sens = {},
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temp = {},
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C = 'C', F = 'F', K = 'K',
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read_temp = read_temp, enable_debug = enable_debug
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}
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_G[modname or 'ds18b20'] = M
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return M

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