# node Module
The node module provides access to system-level features such as sleep, restart and various info and IDs.

## node.restart()

Restarts the chip.

####Syntax
`node.restart()`

####Parameters
`nil`

####Returns
`nil`

####Example
   
```lua
node.restart();
```
___
## node.dsleep()

Enter deep sleep mode, wake up when timed out.

####Syntax
`node.dsleep(us, option)`

**Note:** This function can only be used in the condition that esp8266 PIN32(RST) and PIN8(XPD_DCDC aka GPIO16) are connected together. Using sleep(0) will set no wake up timer, connect a GPIO to pin RST, the chip will wake up by a falling-edge on pin RST.<br />
option=0, init data byte 108 is valuable;<br />
option>0, init data byte 108 is valueless.<br />
More details as follows:<br />
0, RF_CAL or not after deep-sleep wake up, depends on init data byte 108.<br />
1, RF_CAL after deep-sleep wake up, there will belarge current.<br />
2, no RF_CAL after deep-sleep wake up, there will only be small current.<br />
4, disable RF after deep-sleep wake up, just like modem sleep, there will be the smallest current.

####Parameters
 - `us`: number(Integer) or nil, sleep time in micro second. If us = 0, it will sleep forever. If us = nil, will not set sleep time.

 - `option`: number(Integer) or nil. If option = nil, it will use last alive setting as default option.

####Returns
`nil`

####Example

```lua
--do nothing
node.dsleep()
--sleep μs
node.dsleep(1000000)
--set sleep option, then sleep μs
node.dsleep(1000000, 4)
--set sleep option only
node.dsleep(nil,4)
```
___
## node.info()

Returns NodeMCU version, chipid, flashid, flash size, flash mode, flash speed.

####Syntax
`node.info()`

####Parameters
`nil`

####Returns
 - `majorVer` (number)
 - `minorVer` (number)
 - `devVer` (number)
 - `chipid` (number)
 - `flashid` (number)
 - `flashsize` (number)
 - `flashmode` (number)
 - `flashspeed` (number)

####Example

```lua
    majorVer, minorVer, devVer, chipid, flashid, flashsize, flashmode, flashspeed = node.info()
    print("NodeMCU "..majorVer.."."..minorVer.."."..devVer)
```
___
## node.chipid()

Returns the ESP chip ID.

####Syntax
`node.chipid()`

####Parameters
`nil`

####Returns
number:chip ID

####Example

```lua
    id = node.chipid();
```
___
## node.flashid()
Returns the flash chip ID.

####Syntax
`node.flashid()`

####Parameters
`nil`

####Returns
number:flash ID

####Example

```lua
    flashid = node.flashid();
```
___
## node.heap()
Returns the current available heap size in bytes. Note that due to fragmentation, actual allocations of this size may not be possible.

####Syntax
`node.heap()`

####Parameters
`nil`

####Returns
number: system heap size left in bytes

####Example

```lua
    heap_size = node.heap();
```
___
## node.key() --deprecated

Define action to take on button press (on the old devkit 0.9), button connected to GPIO 16.

This function is only available if the firmware was compiled with DEVKIT_VERSION_0_9 defined.


####Syntax
`node.key(type, function)`

####Parameters
  - `type`: type is either string "long" or "short". long: press the key for 3 seconds, short: press shortly(less than 3 seconds)
  - `function`: user defined function which is called when key is pressed. If nil, remove the user defined function. Default function: long: change LED blinking rate,  short: reset chip

####Returns
`nil`

####Example
```lua
    node.key("long", function() print('hello world') end)
```
####See also
  - `node.led()`
___
## node.led() --deprecated

Set the on/off time for the LED (on the old devkit 0.9), with the LED connected to GPIO16, multiplexed with `node.key()`.

This function is only available if the firmware was compiled with DEVKIT_VERSION_0_9 defined.

####Syntax
`node.led(low, high)`

####Parameters
  - `low`: LED off time, LED keeps on when low=0. Unit: milliseconds, time resolution: 80~100ms<br />
  - `high`: LED on time. Unit: milliseconds, time resolution: 80~100ms

####Returns
`nil`

####Example

```lua
    -- turn led on forever.
    node.led(0)
```

####See also
  - `node.key()`
___
## node.input()

Submit a string to the Lua interpreter. Similar to `pcall(loadstring(str))`, but without the single-line limitation.

!!! note "Note:"

  This function only has an effect when invoked from a callback. Using it directly on the console **does not work**.

####Syntax
`node.input(str)`

####Parameters
  - `str`: Lua chunk

####Returns
`nil`

####Example

```lua
    sk:on("receive", function(conn, payload) node.input(payload) end)
```

####See also
  - `node.output()`
___
## node.output()

Redirects the Lua interpreter output to a callback function. Optionally also prints it to the serial console.

!!! note "Note:"

  Do **not** attempt to `print()` or otherwise induce the Lua interpreter to produce output from within the callback function. Doing so results in infinite recursion, and leads to a watchdog-triggered restart.

####Syntax
`node.output(output_fn, serial_debug)`

####Parameters
  - `output_fn(str)`: a function accept every output as str, and can send the output to a socket (or maybe a file).
  - `serial_debug`: 1 output also show in serial. 0: no serial output.

####Returns
`nil`

####Example

```lua
    function tonet(str)
      sk:send(str)
    end
    node.output(tonet, 1)  -- serial also get the lua output.
```

```lua
    -- a simple telnet server
    s=net.createServer(net.TCP)
    s:listen(2323,function(c)
       con_std = c
       function s_output(str)
          if(con_std~=nil)
             then con_std:send(str)
          end
       end
       node.output(s_output, 0)   -- re-direct output to function s_ouput.
       c:on("receive",function(c,l)
          node.input(l)           -- works like pcall(loadstring(l)) but support multiple separate line
       end)
       c:on("disconnection",function(c)
          con_std = nil
          node.output(nil)        -- un-regist the redirect output function, output goes to serial
       end)
    end)
```
####See also
  - `node.input()`
___
## node.readvdd33() --deprecated, moved to adc.readvdd33()
####See also
  - `adc.readvdd33()`
___
## node.compile()

Compile a Lua text file into Lua bytecode, and save it as .lc file.

####Syntax
`node.compile(filename)`

####Parameters
  - `filename`: name of Lua text file

####Returns
`nil`

####Example
```lua
  file.open("hello.lua","w+")
  file.writeline([[print("hello nodemcu")]])
  file.writeline([[print(node.heap())]])
  file.close()

  node.compile("hello.lua")
  dofile("hello.lua")
  dofile("hello.lc")
```
___
## node.setcpufreq()

Change the working CPU Frequency.

####Syntax
`node.setcpufreq(speed)`

####Parameters
  - `speed`: `node.CPU80MHZ` or `node.CPU160MHZ`

####Returns
number:target CPU Frequency

####Example

```lua
    node.setcpufreq(node.CPU80MHZ)
```
___
## node.restore()

Restore system configuration to defaults. Erases all stored WiFi settings, and resets the "esp init data" to the defaults. This function is intended as a last-resort without having to reflash the ESP altogether.

This also uses the SDK function `system_restore()`, which doesn't document precisely what it erases/restores.

####Syntax
`node.restore()`

####Parameters
`nil`

####Returns
`nil`

####Example

```lua
    node.restore()
    node.restart() -- ensure the restored settings take effect
```
___