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ds18b20.lua
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--------------------------------------------------------------------------------
-- DS18B20 one wire module for NODEMCU
-- NODEMCU TEAM
-- LICENCE: http://opensource.org/licenses/MIT
-- Vowstar <[email protected]>
--------------------------------------------------------------------------------
-- Set module name as parameter of require
local modname = ...
local M = {}
_G[modname] = M
--------------------------------------------------------------------------------
-- Local used variables
--------------------------------------------------------------------------------
-- DS18B20 dq pin
local pin = nil
-- DS18B20 default pin
local defaultPin = 9
--------------------------------------------------------------------------------
-- Local used modules
--------------------------------------------------------------------------------
-- Table module
local table = table
-- String module
local string = string
-- One wire module
local ow = ow
-- Timer module
local tmr = tmr
-- Limited to local environment
setfenv(1,M)
--------------------------------------------------------------------------------
-- Implementation
--------------------------------------------------------------------------------
C = 0
F = 1
K = 2
function setup(dq)
pin = dq
if(pin == nil) then
pin = defaultPin
end
ow.setup(pin)
end
function addrs()
setup(pin)
tbl = {}
ow.reset_search(pin)
repeat
addr = ow.search(pin)
if(addr ~= nil) then
table.insert(tbl, addr)
end
tmr.wdclr()
until (addr == nil)
ow.reset_search(pin)
return tbl
end
function readNumber(addr, unit)
result = nil
setup(pin)
flag = false
if(addr == nil) then
ow.reset_search(pin)
count = 0
repeat
count = count + 1
addr = ow.search(pin)
tmr.wdclr()
until((addr ~= nil) or (count > 100))
ow.reset_search(pin)
end
if(addr == nil) then
return result
end
crc = ow.crc8(string.sub(addr,1,7))
if (crc == addr:byte(8)) then
if ((addr:byte(1) == 0x10) or (addr:byte(1) == 0x28)) then
-- print("Device is a DS18S20 family device.")
ow.reset(pin)
ow.select(pin, addr)
ow.write(pin, 0x44, 1)
-- tmr.delay(1000000)
present = ow.reset(pin)
ow.select(pin, addr)
ow.write(pin,0xBE,1)
-- print("P="..present)
data = nil
data = string.char(ow.read(pin))
for i = 1, 8 do
data = data .. string.char(ow.read(pin))
end
-- print(data:byte(1,9))
crc = ow.crc8(string.sub(data,1,8))
-- print("CRC="..crc)
if (crc == data:byte(9)) then
if(unit == nil or unit == C) then
t = (data:byte(1) + data:byte(2) * 256) * 625
elseif(unit == F) then
t = (data:byte(1) + data:byte(2) * 256) * 1125 + 320000
elseif(unit == K) then
t = (data:byte(1) + data:byte(2) * 256) * 625 + 2731500
else
return nil
end
t = t / 10000
-- print("Temperature="..t1.."."..t2.." Centigrade")
-- result = t1.."."..t2
return t
end
tmr.wdclr()
else
-- print("Device family is not recognized.")
end
else
-- print("CRC is not valid!")
end
return result
end
function read(addr, unit)
t = readNumber(addr, unit)
if (t == nil) then
return nil
else
return t
end
end
-- Return module table
return M