nodemcu-firmware/lua_modules/ds18b20/ds18b20-example.lua

local t = require("ds18b20")
local pin = 3 -- gpio0 = 3, gpio2 = 4

local function readout(temps)
  if t.sens then
    print("Total number of DS18B20 sensors: ".. #t.sens)
    for i, s in ipairs(t.sens) do
      print(string.format("  sensor #%d address: %s%s",  i,
        ('%02X:%02X:%02X:%02X:%02X:%02X:%02X:%02X'):format(s:byte(1,8)),
        s:byte(9) == 1 and " (parasite)" or ""))
      end
  end

  for addr, temp in pairs(temps) do
    print(string.format("Sensor %s: %s °C", ('%02X:%02X:%02X:%02X:%02X:%02X:%02X:%02X'):format(addr:byte(1,8)), temp))
  end

  -- Module can be released when it is no longer needed
  --t = nil
  --package.loaded["ds18b20"]=nil
end

do
  t:enable_debug()
  file.remove("ds18b20_save.lc") -- remove saved addresses
  print("=============================================", node.heap())
  print("first call, no addresses in flash, search is performed")
  t:read_temp(readout, pin, t.C)

  tmr.create():alarm(2000, tmr.ALARM_SINGLE, function()
    print("=============================================", node.heap())
    print("second readout, no new search, found addresses are used")
    t:read_temp(readout, pin)

    tmr.create():alarm(2000, tmr.ALARM_SINGLE, function()
      print("=============================================", node.heap())
      print("force search again")
      t:read_temp(readout, pin, nil, true)

      tmr.create():alarm(2000, tmr.ALARM_SINGLE, function()
        print("=============================================", node.heap())
        print("save search results")
        t:read_temp(readout, pin, nil, false, true)

        tmr.create():alarm(2000, tmr.ALARM_SINGLE, function()
          print("=============================================", node.heap())
          print("use saved addresses")
          t.sens={}
          t:read_temp(readout, pin)
        end)
      end)
    end)
  end)
end