DS18B20 on NodeMCU Lua

ds18b20-async.lua

--------------------------------------------------------------------------------
-- DS18B20 one wire module for NODEMCU
-- by @voborsky
--------------------------------------------------------------------------------

return({
  pin=3,
  sens={},
  temp={},
  
  conversion = function(self)
    local pin = self.pin
    for i,s in ipairs(self.sens) do
      if s.status == 0 then
	print("starting conversion:", encoder.toBase64(s.addr), s.parasite == 1 and "parasite" or " ")
	ow.reset(pin)
	ow.select(pin, s.addr)   -- select the sensor
	ow.write(pin, 0x44, 1)  -- and start conversion
	s.status = 1
	if s.parasite == 1 then break end -- parasite sensor blocks bus during conversion
      end
    end
    tmr.alarm(tmr.create(), 750, tmr.ALARM_SINGLE, function() self:readout() end)
  end,
  
  readTemp = function(self, cb, lpin)
    local pin = self.pin
    self.cb = cb
        self.temp={}
    if lpin then pin = lpin end
    ow.setup(pin)

    self.sens={}
    ow.reset_search(pin)
    -- ow.target_search(pin,0x28)
    -- search the first device
    local addr = ow.search(pin)
    -- and loop through all devices
    while addr do
      -- search next device
      local crc=ow.crc8(string.sub(addr,1,7))
      if (crc==addr:byte(8)) and ((addr:byte(1)==0x10) or (addr:byte(1)==0x28)) then
        ow.reset(pin)
        ow.select(pin, addr)   -- select the found sensor
        ow.write(pin, 0xB4, 1) -- Read Power Supply [B4h]
        local parasite = (ow.read(pin)==0 and 1 or 0)
        table.insert(self.sens,{addr=addr, parasite=parasite, status=0})
        print("contact: ", encoder.toBase64(addr), parasite == 1 and "parasite" or " ")
      end

      addr = ow.search(pin)
      tmr.wdclr()
    end
      
    -- place powered sensors first
    table.sort(self.sens, function(a,b) return a.parasite<b.parasite end)
    
    node.task.post(node.task.MEDIUM_PRIORITY, function() self:conversion() end)
  end,
  
  readout=function(self)
    local pin = self.pin
    local next = false
        if not self.sens then return 0 end
    for i,s in ipairs(self.sens) do
      --print(encoder.toBase64(s.addr), s.status)
      if s.status == 1 then
        ow.reset(pin)
        ow.select(pin, s.addr)   -- select the  sensor
        ow.write(pin, 0xBE, 0) -- READ_SCRATCHPAD
        data = ow.read_bytes(pin, 9)

        local t=(data:byte(1)+data:byte(2)*256)
        if (t > 0x7fff) then t = t - 0x10000 end
        if (s.addr:byte(1) == 0x28) then
          t = t * 625  -- DS18B20, 4 fractional bits
        else
          t = t * 5000 -- DS18S20, 1 fractional bit
        end

        local sgn = t<0 and -1 or 1
        local tA = sgn*t
        local tH=tA/10000
        local tL=(tA%10000)/1000 + ((tA%1000)/100 >= 5 and 1 or 0)
              
        if tH and (tH~=85) then
          self.temp[s.addr]=(sgn<0 and "-" or "")..tH.."."..tL
          print(encoder.toBase64(s.addr),(sgn<0 and "-" or "")..tH.."."..tL)
          s.status = 2
        end
      end
      next = next or s.status == 0
    end
    if next then 
      node.task.post(node.task.MEDIUM_PRIORITY, function() self:conversion()  end)
    else
      self.sens = nil
      if self.cb then 
        node.task.post(node.task.MEDIUM_PRIORITY, function()  self.cb(self.temp) end) 
      end
    end
    
  end
})