nodemcu-firmware/README.md

# **nodeMcu API Instruction** #
###version 0.1 2014-10-11
###change log: 

2014-11-5<br />
delete log operation api from node module<br />
add log module<br />
modify wifi module api<br />
modify node.key long_press and short_press default function<br />
key is triged only when key is released<br />


# Summary
- Easy to access wireless router
- Based on Lua 5.1.4，Developer are supposed to have experience in Lua Program language.
- Try to use Event-Drive programming modal.
- In-side  timer，pwm，i2c，net，gpio，wifi module.
- Serial Port BaudRate:74880
- Re-indexing the 8266 pin，use the index to program gpio，i2c，pwm.
- Index vs Pin-number Table:

<table>
  <tr>
    <th scope="col">IO index</th><th scope="col">ESP8266 pin</th><th scope="col">IO index</th><th scope="col">ESP8266 pin</th>
  </tr>
  <tr>
    <td>0</td><td>GPIO12</td><td>8</td><td>GPIO0</td>
  </tr>
  <tr>
    <td>1</td><td>GPIO13</td><td>9</td><td>GPIO2</td>
   </tr>
   <tr>
    <td>2</td><td>GPIO14</td><td>10</td><td>GPIO4</td>
  </tr>
  <tr>
    <td>3</td><td>GPIO15</td><td>11</td><td>GPIO5</td>
   </tr>
   <tr>
    <td>4</td><td>GPIO3</td><td></td><td></td>
  </tr>
  <tr>
    <td>5</td><td>GPIO1</td><td></td><td></td>
   </tr>
   <tr>
    <td>6</td><td>GPIO9</td><td></td><td></td>
  </tr>
  <tr>
    <td>7</td><td>GPIO10</td<td></td><td></td>
   </tr>
</table>


#Firmware Program
###Address

eagle.app.v6.flash.bin: 0x00000<br />
eagle.app.v6.irom0text.bin: 0x10000<br />
esp_init_data_default.bin: 0x7c000<br />
blank.bin: 0x7e000


#node module
<a id="nm_restart"></a>
## node.restart()
####Description
module restart.

####Syntax

node.restart()

####Parameters
nil

####Returns
nil

####Example
   
```
    node.restart();
```

####See also
**-**   []()

<a id="nm_dsleep"></a>
## node.dsleep()
####Description

enter deep sleep mode for us micro seconds，restart when timed out<br />
us: sleep time in micro second

####Syntax

node.dsleep(us)<br />
**-Note:** This function can only be used in the condition of connecting esp8266 PIN32(rst) and PIN8(XPD_DCDC) together.

####Parameters
us:sleep time in micro second

####Returns
nil

####Example

```
    node.dsleep(us);
```

####See also
**-**   []()

<a id="nm_chipid"></a>
## node.chipid()
####Description
return chip identifier

####Syntax
node.chipid()

####Parameters
nil

####Returns
number:chip identifier

####Example

```
    id = node.chipid();
```

####See also
**-**   []()

<a id="nm_heap"></a>
## node.heap()
####Description
return the available RAM size in bytes

####Syntax
node.heap()

####Parameters
nil

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

####Example

```
    heap_size = node.heap();
```

####See also
**-**   []()

<a id="nm_key"></a>
## node.key()
####Description
define button function.

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

####Parameters
type: type is either string "long" or "short". long: press the button for 3 seconds, short: press shortly(less than 3 seconds)<br />
function(): user defined function for button. If nil, cancling the user defined function, function are initialized to default.<br />
Default function: long: change LED blinking rate,  short: reset chip

####Returns
nil

####Example    
```
    node.key("long", function(){print('hello world')})
```

####See also
**-**   []()

<a id="nm_led"></a>
## node.led()
####Description
setup the on/off time for led

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

####Parameters
Low: LED off time, 0 for LED keeps on. Unit: milliseconds, time resolution: 80~100ms<br />
High: LED off time. Unit: milliseconds, time resolution: 80~100ms

####Returns
nil

####Example

```
    //turn led on forever.
    node.led(0);
```

####See also
**-**   []()

#log module
<a id="lg_format"></a>
## log.format()
####Description
format flash for users.

####Syntax
log.format()

####Parameters
nil

####Returns
nil

####Example

```
    //record log to init.lua. Call the file after system restart.
    log.format()
    log.start("init.lua", 1)
    print("hello world")
    log.stop()
```

####See also
**-**   [log.start()](#lg_start)<br />
**-**   [log.stop()](#lg_stop)

<a id="lg_start"></a>
## log.start()
####Description
start to log input

####Syntax
log.start(filename, noparse)

####Parameters

filename: log file, directories are not supported<br />
noparse: 1 for lua VM doesn’t parse input, 0 for lua VM parse input

####Returns
nil

####Example

```
    //record log to init.lua. Call the file after system restart.
    log.format()
    log.start("init.lua", 1)
    print("hello world")
    log.stop()
    //At this point, the content of init.lua is "print("hello world")". When system restart, print("hello world") are excuted.
```

####See also
**-**   [log.format()](#lg_format)<br />
**-**   [log.stop()](#lg_stop)

<a id="lg_stop"></a>
## log.stop()
####Description
stop log.

####Syntax
log.stop()

####Parameters
nil

####Returns
nil

####Example

```
    //record log to init.lua. Call the file after system restart.
    log.format()
    log.start("init.lua", 1)
    print("hello world")
    log.stop()
    //At this point, the content of init.lua is "print("hello world")". When system restart, print("hello world") are excuted.
```

####See also
**-**   [log.format()](#lg_format)<br />
**-**   [log.start()](#lg_start)

<a id="lg_open"></a>
## log.open()
####Description
open the log file

####Syntax
log.open(filename)

####Parameters
filename: log file, directories are not supported

####Returns
nil

####Example

```
    //print the first line of 'init.lua'
    log.open("init.lua")
    print(log.readline())
    log.close()
```

####See also
**-**   [log.close()](#lg_close)<br />
**-**   [log.readline()](#lg_readline)

<a id="lg_close"></a>
## log.close()
####Description
close the log file which opened before

####Syntax
log.close()

####Parameters
nil

####Returns
nil

####Example

```
    //print the first line of 'init.lua'
    log.open("init.lua")
    print(log.readline())
    log.close()
```

####See also
**-**   [log.open()](#lg_open)<br />
**-**   [log.readline()](#lg_readline)

<a id="lg_readline"></a>
## log.readline()
####Description
read log file which is opened before line by line.

####Syntax
log.readline()

####Parameters
nil

####Returns
log file content in string, line by line

####Example

```
    //print the first line of 'init.lua'
    log.open("init.lua")
    print(log.readline())
    log.close()
```

####See also
**-**   [log.open()](#lg_open)
**-**   [log.close()](#lg_close)

<a id="lg_list"></a>
## log.list()
####Description
list all files.

####Syntax
log.list()

####Parameters
nil

####Returns
a lua table which contains the {file name: file size} pairs

####Example

```
    l = log.list();
    for k,v in l do
      print("name:"..k..", size:"..v)
    end
```

####See also
**-**   [log.format()](#lg_format)

#wifi module
##CONSTANT
wifi.STATION, wifi.SOFTAP, wifi.STATIONAP

<a id="wf_setmode"></a>
## wifi.setmode(mode)
####Description
set wifi operation mode.

####Syntax
wifi.setmode(mode)

####Parameters
mode: value should be: wifi. STATION, wifi.SOFTAP or wifi.STATIONAP

####Returns
current mode after setup

####Example

```
    wifi.setmode(wifi.STATION)
```

####See also
**-**   [wifi.getmode()](#wf_getmode)


<a id="wf_getmode"></a>
## wifi.getmode(mode)
####Description
get wifi operation mode.

####Syntax
wifi.getmode()

####Parameters
nil

####Returns
wifi operation mode

####Example

```
    print(wifi.getmode())
```

####See also
**-**   [wifi.setmode()](#wf_setmode)


<a id="wf_startsmart"></a>
## wifi.startsmart()
####Description
starts to auto configuration，if success set up ssid and pwd automatically .

####Syntax
wifi.startsmart(channel, function succeed_callback())

####Parameters

channel: 1~13，startup channel for searching, if nil, default to 6.  20 seconds for each channel.<br />
succeed_callback: callback function for success configuration, which is called after getting the password and the connection to AP.

####Returns
nil

####Example

```
    wifi.startsmart(6, cb())
```

####See also
**-**   [wifi.stopsmart()](#wf_stopsmart)


<a id="wf_stopsmart"></a>
## wifi.stopsmart()
####Description
stop the configuring process.

####Syntax
wifi.stopsmart()

####Parameters
nil

####Returns
nil

####Example

```
    wifi.stopsmart()
```

####See also
**-**   [wifi.startsmart()](#wf_startsmart)


#wifi.sta module

<a id="ws_config"></a>
## wifi.sta.config()
####Description
set ssid and password in station mode.

####Syntax
wifi.sta.config(ssid, password)

####Parameters

ssid: string which is less than 32 bytes.<br />
password: string which is less than 64 bytes.

####Returns
nil

####Example

```
    wifi.sta.config("myssid","mypassword")
```

####See also
**-**   [wifi.sta.connect()](#ws_connect)<br />
**-**   [wifi.sta.disconnect()](#ws_disconnect)


<a id="ws_connect"></a>
## wifi.sta.connect()
####Description
connect to AP in station mode.

####Syntax
wifi.sta.connect()

####Parameters
nil


####Returns
nil

####Example

```
    wifi.sta.connect()
```

####See also
**-**   [wifi.sta.disconnect()](#ws_disconnect)<br />
**-**   [wifi.sta.config()](#ws_config)


<a id="ws_disconnect"></a>
## wifi.sta.disconnect()
####Description
disconnect from AP in station mode.

####Syntax
wifi.sta.disconnect()

####Parameters
nil


####Returns
nil

####Example

```
    wifi.sta.disconnect()
```

####See also
**-**   [wifi.sta..config()](#ws_config)<br />
**-**   [wifi.sta.connect()](#ws_connect)


<a id="ws_autoconnect"></a>
## wifi.sta.autoconnect()
####Description
auto connect to AP in station mode.

####Syntax
wifi.sta.autoconnect(auto)

####Parameters
auto: 0 to disable auto connecting. 1 to enable auto connecting


####Returns
nil

####Example

```
    wifi.sta.autoconnect()
```

####See also
**-**   [wifi.sta..config()](#ws_config)<br />
**-**   [wifi.sta.connect()](#ws_connect)<br />
**-**   [wifi.sta.disconnect()](#ws_disconnect)


<a id="ws_getip"></a>
## wifi.sta.getip()
####Description
get ip address in station mode.

####Syntax
wifi.sta.getip()

####Parameters
nil


####Returns
ip address in string, for example:"192.168.0.111"

####Example

```
    //print current ip
    print(wifi.sta.getip())
```

####See also
**-**   [wifi.sta.getmac()](#ws_getmac)


<a id="ws_getmac"></a>
## wifi.sta.getmac()
####Description
get mac address in station mode.

####Syntax
wifi.sta.getmac()

####Parameters
nil


####Returns
mac address in string, for example:"18-33-44-FE-55-BB"

####Example

```
    //print current mac address
    print(wifi.sta.getmac())
```

####See also
**-**   [wifi.sta..getip()](#ws_getip)


#wifi.ap module

<a id="wa_config"></a>
## wifi.ap.config()
####Description
set ssid and password in ap mode.

####Syntax
wifi.ap.config(cfg)

####Parameters
cfg: lua table to setup ap.

####Example:

```
     cfg={}
     cfg.ssid="myssid"
     cfg.pwd="mypwd"
     wifi.ap.setconfig(cfg)
```

####Returns
nil

####Example

```
    wifi.ap.config(ssid, 'password')
```

####See also
**-**    []()

<a id="wa_getip"></a>
## wifi.ap.getip()
####Description
get ip in ap mode.

####Syntax
wifi.ap.getip()

####Parameters
nil

####Returns
ip address in string, for example:"192.168.0.111"

####Example

```
    wifi.ap.getip()
```

####See also
**-**   [wifi.ap..getmac()](#wa_getmac)


<a id="wa_getmac"></a>
## wifi.ap.getmac()
####Description
get mac address in ap mode.

####Syntax
wifi.ap.getmac()

####Parameters
nil

####Returns
mac address in string, for example:"1A-33-44-FE-55-BB"

####Example

```
    wifi.ap.getmac()
```

####See also
**-**   [wifi.ap.getip()](#wa_getip)


#timer module
<a id="tm_delay"></a>
## tmr.delay()
####Description
delay us micro seconds.

####Syntax
tmr.dealy(us)

####Parameters
us: delay time in micro second

####Returns
nil

####Example

```
    //delay 100us
    tmr.delay(100)
```

####See also
**-**   [tmr.now()](#tm_now)


<a id="tm_now"></a>
## tmr.now()
####Description
return the current value of system counter: uint32, loopback, us.

####Syntax
tmr.now()

####Parameters
nil

####Returns
uint32: value of counter

####Example

```
    //print current value of counter
    print(tmr.now())
```

####See also
**-**   [tmr.delay()](#tm_delay)


<a id="tm_alarm"></a>
## tmr.alarm()
####Description
alarm time.

####Syntax
tmr.alarm(interval, repeat, function do())

####Parameters
Interval: alarm time, unit: millisecond<br />
repeat: 0 - one time alarm, 1 - repeat<br />
function do(): callback function for alarm timed out

####Returns
nil

####Example

```
    //print "hello world" every 1000ms
    tmr.alarm(1000, 1, function() print("hello world") end )
```

####See also
**-**   [tmr.now()](#tm_now)


<a id="tm_stop"></a>
## tmr.stop()
####Description

stop alarm.<br />
**-Note:** only one alarm is allowed, the previous one would be replaced if tmr.alarm() again before tmr.stop().

####Syntax
tmr.stop()

####Parameters
nil.

####Returns
nil

####Example

```
    //print "hello world" every 1000ms
    tmr.alarm(1000, 1, function() print("hello world") end )

    //something else

    //stop alarm
    tmr.stop()
```

####See also
**-**   [tmr.now()](#tm_now)


#GPIO module
##CONSTANT
gpio.OUTPUT, gpio.INPUT, gpio.INT, gpio.HIGH, gpio.LOW


<a id="io_mode"></a>
## gpio.mode()
####Description
initialize pin to GPIO mode, set the pin in/out mode.

####Syntax
gpio.mode(pin, mode)

####Parameters
pin: 0~11，IO index<br />
mode: gpio.OUTPUT or gpio.INPUT, or gpio.INT(interrupt mode)

####Returns
nil

####Example

```
    //set gpio 0 as output.
    gpio.mode(0, gpio.OUTPUT)

```

####See also
**-**   [gpio.read()](#io_read)


<a id="io_read"></a>
## gpio.read()
####Description
read pin value.

####Syntax
gpio.read(pin)

####Parameters
pin: 0~11，IO index

####Returns
number:0 - low, 1 - high

####Example

```
    //read value of gpio 0.
    gpio.read(0)
```

####See also
**-**   [gpio.mode()](#io_mode)


<a id="io_write"></a>
## gpio.write()
####Description
set pin value.

####Syntax
gpio.write(pin)

####Parameters
pin: 0~11，IO index<br />
level: gpio.HIGH or gpio.LOW

####Returns
nil

####Example

```
    //set pin index 1 to GPIO mode, and set the pin to high.
    pin=1
    gpio.mode(pin, gpio.OUTPUT)
    gpio.write(pin, gpio.HIGH)
```

####See also
**-**   [gpio.mode()](#io_mode)<br />
**-**   [gpio.read()](#io_read)


<a id="io_trig"></a>
## gpio.trig()
####Description
set the interrupt callback function for pin.

####Syntax
gpio.trig(pin, type, function(level))

####Parameters
pin: 0~11，IO index<br />
type: "up", "down", "both", "low", "high", which represent rising edge, falling edge, both edge, low level, high level trig mode separately.<br />
function(level): callback function when triggered. The gpio level is the param. Use previous callback function if undefined here.

####Returns
nil

####Example

```
    //use pin 0 as the input pulse width counter
    pulse0 = 0
    du = 0
    gpio.mode(0,gpio.INT)
    function pin0cb(level)
     du = tmr.now() – pulse0
     print(du)
     pulse0 = tmr.now()
     if level == 1 then gpio.trig(0, "down ") else gpio.trig(0, "up ") end
    end
    gpio.trig(0, "down ",pin0cb)

```

####See also
**-**   [gpio.mode()](#io_mode)<br />
**-**   [gpio.write()](#io_write)


#PWM module
<a id="pw_setup"></a>
## pwm.setup()
####Description
set pin to PWM mode. Only 3 pins can be set to PWM mode at the most.

####Syntax
pwm.setup(pin, clock, duty)

####Parameters
pin: 0~11，IO index<br />
clock: 1~500，pwm frequency<br />
duty: 0~100，pwm duty cycle in percentage

####Returns
nil

####Example

```
    //set pin index 0 as pwm output, frequency is 100Hz, duty cycle is 50-50..
    pwm.setup(0, 100, 50)
```

####See also
**-**   [pwm.start()](#pw_start)


<a id="pw_close"></a>
## pwm.close()
####Description
quit PWM mode for specified pin.

####Syntax
pwm.close(pin)

####Parameters
pin: 0~11，IO index

####Returns
nil

####Example

```
    pwm.close(0)
```

####See also
**-**   [pwm.start()](#pw_start)


<a id="pw_start"></a>
## pwm.start()
####Description
pwm starts, you can detect the waveform on the gpio.

####Syntax
pwm.start(pin)

####Parameters
pin: 0~11，IO index

####Returns
nil

####Example

```
    pwm.start(0)
```

####See also
**-**   [pwm.stop()](#pw_stop)


<a id="pw_stop"></a>
## pwm.stop()
####Description
pause the output of PWM waveform.

####Syntax
pwm.stop(pin)

####Parameters
pin: 0~11，IO index

####Returns
nil

####Example

```
    pwm.stop(0)
```

####See also
**-**   [pwm.start()](#pw_start)


<a id="pw_setclock"></a>
## pwm.setclock()
####Description

set pwm frequency for pin.<br />
**-Note:** setup pwm frequency will synchronously change others if there are any. Only one PWM frequency can be allowed for the system.

####Syntax
pwm.setclock(pin, clock)

####Parameters
pin: 0~11，IO index.<br />
clock: 1~500, pwm frequency.

####Returns
nil

####Example

```
    pwm.setclock(0, 100)
```

####See also
**-**   [pwm.getclock()](#pw_getclock)


<a id="pw_getclock"></a>
## pwm.getclock()
####Description
get pwm frequency of pin.

####Syntax
pwm.getclock(pin)

####Parameters
pin: 0~11，IO index.

####Returns
number:pwm frequency of pin

####Example

```
    print(pwm.getclock(0))
```

####See also
**-**   [pwm.setclock()](#pw_setclock)


<a id="pw_setduty"></a>
## pwm.setduty()
####Description
set duty clycle for pin.

####Syntax
pwm.setduty(pin, duty)

####Parameters
pin: 0~11，IO index<br />
duty: 0~100，pwm duty cycle in percentage

####Returns
nil

####Example

```
    pwm.setduty(0, 50)
```

####See also
**-**   [pwm.getduty()](#pw_getduty)


<a id="pw_getduty"></a>
## pwm.getduty()
####Description
get duty clycle for pin.

####Syntax
pwm.getduty(pin)

####Parameters
pin: 0~11，IO index

####Returns
nil

####Example

```
    //D0 is connected to green led
    //D1 is connected to blue led
    //D2 is connected to red led
    pwm.setup(0,500,50)
    pwm.setup(1,500,50)
    pwm.setup(2,500,50)
    pwm.start(0)
    pwm.start(1)
    pwm.start(2)
    function led(r,g,b)
      pwm.setduty(0,g)
      pwm.setduty(1,b)
      pwm.setduty(2,r)
    end
    led(50,0,0)	// set led to red
    led(0,0,50)	//set led to blue.

```

####See also
**-**   [pwm.setduty()](#pw_setduty)


#net module
##CONSTANT
net.TCP, net.UDP

<a id="nt_createServer"></a>
## net.createServer()
####Description
create a server.

####Syntax
net.createServer(type, secure)

####Parameters
type: net.TCP or net.UDP<br />
secure: true or false, true for safe link, false for ordinary link

####Returns
net.server sub module

####Example

```
    net.createServer(net.TCP, true)
```

####See also
**-**   [net.createConnection()](#nt_createConnection)


<a id="nt_createConnection"></a>
## net.createConnection()
####Description
create a client.

####Syntax
net.createConnection(type, secure)

####Parameters
type: net.TCP or net.UDP<br />
secure: true or false, true for safe link, false for ordinary link

####Returns
net.server sub module

####Example

```
    net.createConnection(net.UDP, false)
```

####See also
**-**   [net.createServer()](#nt_createServer)


#net.server module
<a id="ns_listen"></a>
## listen()
####Description
listen on port from [ip] address.

####Syntax
net.server.listen(port,[ip],function(net.socket))

####Parameters
port: port number<br />
ip:ip address string, can be omitted<br />
function(net.socket): callback function, pass to Caller function as param if a connection is created successfully

####Returns
nil

####Example

```
    //create a server
    sv=net.createServer(net.TCP, false)
    //server listen on 80, if data received, print data to console, and send "hello world" to remote.
    sv:listen(80,function(c)
    	c:on("receive", function(sck, pl) print(pl) end)
    	c:send("hello world")
    	end)
```

####See also
**-**   [net.createServer()](#nt_createServer)


<a id="ns_close"></a>
## close()
####Description
close server.

####Syntax
net.server.close()

####Parameters
nil

####Returns
nil

####Example

```
    //create a server
    sv=net.createServer(net.TCP, false)
    //close server
    sv:close()
```

####See also
**-**   [net.createServer()](#nt_createServer)


#net.socket module
<a id="nk_connect"></a>
## connect()
####Description
connect to remote.

####Syntax
connect(port, ip)

####Parameters
port: port number<br />
ip: ip address in string

####Returns
nil

####See also
**-**   [net.socket:on()](#nk_on)


<a id="nk_send"></a>
## send()
####Description
send data to remote via connection.

####Syntax
send(string, function(sent))

####Parameters
string: data in string which will be sent to remote<br />
function(sent): callback function for sending string

####Returns
nil

####See also
**-**   [net.socket:on()](#nk_on)


<a id="nk_on"></a>
## on()
####Description
register callback function for event.

####Syntax
on(event, function cb())

####Parameters
event: string, which can be: "connection"，"reconnection"，"disconnection"，"receive"，"sent"<br />
function cb(net.socket, [string]): callback function. The first param is the socket.<br />
If  event is"receive"， the second param is received data in string.

####Returns
nil

####Example

```
    sk=net.createConnection(net.TCP, false)
    sk:on("receive", function(sck, c) print(c) end )
    sk:connect(80,"192.168.0.66")
    sk:send("GET / HTTP/1.1\r\nHost: 192.168.0.66\r\nConnection: keep-alive\r\nAccept: */*\r\n\r\n")
```

####See also
**-**   [net.createServer()](#nt_createServer)


<a id="nk_close"></a>
## close()
####Description
close socket.

####Syntax
close()

####Parameters
nil

####Returns
nil

####See also
**-**   [net.createServer()](#nt_createServer)


<a id="nk_dns"></a>
## dns()
####Description
get domain ip

####Syntax
dns(domain, function(net.socket, ip))

####Parameters
domain: domain name.<br />
function (net.socket, ip): callback function. The first param is the socket, the second param is the ip address in string.

####Returns
nil

####See also
**-**   [net.createServer()](#nt_createServer)


#i2c module
##CONSTANT
i2c.SLOW,  i2c.TRANSMITTER, i2c. RECEIVER.  FAST（400k）is not supported for now.

<a id="ic_setup"></a>
## i2c.setup()
####Description
initialize i2c.

####Syntax
i2c.setup(id, pinSDA, pinSCL, speed)

####Parameters
id = 0<br />
pinSDA: 0~11，IO index<br />
pinSCL: 0~11，IO index<br />
speed:  i2c.SLOW

####Returns
nil

####See also
**-**   [i2c.read()](#ic_read)


<a id="ic_start"></a>
## i2c.start()
####Description
start i2c transporting.

####Syntax
i2c.start(id)

####Parameters
id = 0

####Returns
nil

####See also
**-**   [i2c.read()](#ic_read)


<a id="ic_stop"></a>
## i2c.stop()
####Description
stop i2c transporting.

####Syntax
i2c.stop(id)

####Parameters
id = 0

####Returns
nil

####See also
**-**   [i2c.read()](#ic_read)


<a id="ic_address"></a>
## i2c.address()
####Description
setup i2c address and read/write mode.

####Syntax
i2c.address(id, device_addr, direction)

####Parameters
id=0<br />
device_addr: device address.<br />
direction: i2c.TRANSMITTER for writing mode , i2c. RECEIVER for reading mode

####Returns
nil

####See also
**-**   [i2c.read()](#ic_read)

<a id="ic_write"></a>
## i2c.write()
####Description
write data to i2c, data can be multi numbers, string or lua table.

####Syntax
i2c.write(id, data1, data2,...)

####Parameters
id=0<br />
data: data can be numbers, string or lua table.

####Returns
nil

####Example

```
    i2c.write(0, "hello", "world")
```

####See also
**-**   [i2c.read()](#ic_read)


<a id="ic_read"></a>
## i2c.read()
####Description
read data for len bytes.

####Syntax
i2c.read(id, len)

####Parameters
id=0<br />
len: data length

####Returns
string:data received.

####Example

```
    id=0
    sda=1
    scl=0

    //initialize i2c, set pin1 as sda, set pin0 as scl
    i2c.setup(id,sda,scl,i2c.SLOW)

    //user defined function: read from reg_addr content of dev_addr
    function read_reg(dev_addr, reg_addr)
      i2c.start(id)
      i2c.address(id, dev_addr ,i2c.TRANSMITTER)
      i2c.write(id,reg_addr)
      i2c.stop(id)
      i2c.start(id)
      i2c.address(id, dev_addr,i2c.RECEIVER)
      c=i2c.read(id,1)
      i2c.stop(id)
      return c
    end

    //get content of register 0xAA of device 0x77
    reg = read_reg(0x77, 0xAA)
    pirnt(string.byte(reg))

```

####See also
**-**   [i2c.write()](#ic_write)