Add support to DHT11 and add some comments.

Change function names.
read->-read11() support DHT11
        ->read22() support DHT21 DHT22

lua_modules/dht22/dht_lib.lua

@@ -1,34 +1,43 @@
 -- ***************************************************************************
--- DHT22 module for ESP8266 with nodeMCU
+-- DHTxx(11,21,22) module for ESP8266 with nodeMCU
 --
--- Written by Javier Yanez 
+-- Written by Javier Yanez mod by Martin
 -- but based on a script of Pigs Fly from ESP8266.com forum
 --
 -- MIT license, http://opensource.org/licenses/MIT
 -- ***************************************************************************
 
+--Support list：
+--DHT11 Tested ->read11
+--DHT21 Not Tested->read22
+--DHT22 Tested->read22
+
+--==========================Module Part======================
 local moduleName = ...
 local M = {}
 _G[moduleName] = M
-
+--==========================Local the UMI and TEMP===========
 local humidity
 local temperature
+--==========================Local the bitStream==============
+local bitStream = {}
 
-function M.read(pin)
-  local checksum
-  local checksumTest
+---------------------------Read bitStream from DHTXX--------------------------
+local function read(pin)
+
+  local bitlength = 0
   humidity = 0
   temperature = 0
-  checksum = 0
 
   -- Use Markus Gritsch trick to speed up read/write on GPIO
   local gpio_read = gpio.read
   
-  local bitStream = {}
+  
   for j = 1, 40, 1 do
     bitStream[j] = 0
   end
-  local bitlength = 0
+
+  
 
   -- Step 1:  send out start signal to DHT22
   gpio.mode(pin, gpio.OUTPUT)
@@ -39,7 +48,7 @@ function M.read(pin)
   gpio.write(pin, gpio.HIGH)
   gpio.mode(pin, gpio.INPUT)
 
-  -- Step 2:  DHT22 send response signal 
+  -- Step 2:  Receive bitStream from DHT11/22
   -- bus will always let up eventually, don't bother with timeout
   while (gpio_read(pin) == 0 ) do end
   local c=0
@@ -59,8 +68,53 @@ function M.read(pin)
     -- bus will always let up eventually, don't bother with timeout
     while (gpio_read(pin) == 0) do end
   end
-
+end
+---------------------------Convert the bitStream into Number through DHT11 Ways--------------------------
+function M.read11(pin)
+--As for DHT11 40Bit is consisit of 5Bytes
+--First byte->Humidity Data's Int part
+--Sencond byte->Humidity Data's Float Part(Which should be empty)
+--Third byte->Temp Data;s Intpart
+--Forth byte->Temp Data's Float Part(Which should be empty)
+--Fifth byte->SUM Byte, Humi+Temp
+  read(pin)
+ local checksum = 0
+ local checksumTest
   --DHT data acquired, process.
+  for i = 1, 8, 1 do -- Byte[0]
+    if (bitStream[i] > 3) then
+      humidity = humidity + 2 ^ (8 - i)
+    end
+  end
+  for i = 1, 8, 1 do -- Byte[2]
+    if (bitStream[i + 16] > 3) then
+      temperature = temperature + 2 ^ (8 - i)
+    end
+  end
+  for i = 1, 8, 1 do --Byte[4]
+    if (bitStream[i + 32] > 3) then
+      checksum = checksum + 2 ^ (8 - i)
+    end
+  end
+
+  if(checksum ~= humidity+temperature) then
+    humidity = nil
+    temperature = nil
+  end
+  
+end
+---------------------------Convert the bitStream into Number through DHT22 Ways--------------------------
+function M.read22( pin )
+--As for DHT22 40Bit is consisit of 5Bytes
+--First byte->Humidity Data's High Bit
+--Sencond byte->Humidity Data's Low Bit(And if over 0x8000, use complement)
+--Third byte->Temp Data's High Bit
+--Forth byte->Temp Data's Low Bit
+--Fifth byte->SUM Byte
+  read(pin)
+  local checksum = 0
+  local checksumTest
+   --DHT data acquired, process.
   for i = 1, 16, 1 do
     if (bitStream[i] > 3) then
       humidity = humidity + 2 ^ (16 - i)
@@ -91,6 +145,7 @@ function M.read(pin)
   end
 end
 
+---------------------------Check out the data--------------------------
 function M.getTemperature()
   return temperature
 end