add encoder doc

docs/en/modules/encoder.md

@@ -0,0 +1,82 @@
+# encoder Module
+| Since  | Origin / Contributor  | Maintainer  | Source  |
+| :----- | :-------------------- | :---------- | :------ |
+| 2016-02-26 | [Terry Ellison](https://github.com/TerryE) | [Terry Ellison](https://github.com/TerryE) | [encoder.c](../../../app/modules/encoder.c)|
+
+The encoder modules provides various functions for encoding and decoding byte data.
+
+## encoder.toBase64()
+
+Provides a Base64 representation of a (binary) Lua string.
+
+#### Syntax
+`b64 = encoder.toBase64(binary)`
+
+#### Parameters
+`binary` input string to Base64 encode
+
+#### Return
+A Base64 encoded string.
+
+#### Example
+```lua
+print(encoder.toBase64(crypto.hash("sha1","abc")))
+```
+
+## encoder.fromBase64()
+
+Decodes a Base64 representation of a (binary) Lua string back into the original string.  An error is
+thrown if the string is not a valid base64 encoding.
+
+#### Syntax
+`binary_string = encoder.toBase64(b64)`
+
+#### Parameters
+`b64` Base64 encoded input string 
+
+#### Return
+The decoded Lua (binary) string.
+
+#### Example
+```lua
+print(encoder.fromBase64(encoder.toBase64("hello world")))
+```
+
+## encoder.toHex()
+
+Provides an ASCII hex representation of a (binary) Lua string. Each byte in the input string is
+represented as two hex characters in the output.
+
+#### Syntax
+`hexstr = encoder.toHex(binary)`
+
+#### Parameters
+`binary` input string to get hex representation for
+
+#### Returns
+An ASCII hex string.
+
+#### Example
+```lua
+print(encoder.toHex(crypto.hash("sha1","abc")))
+```
+
+## encoder.fromHex()
+
+Returns the Lua binary string decode of a ASCII hex string. Each byte in the output string is
+represented as two hex characters in the input.  An error is thrown if the string is not a 
+valid base64 encoding.
+
+#### Syntax
+`binary = encoder.fromHex(hexstr)`
+
+#### Parameters
+`hexstr`  An ASCII hex string.
+
+#### Returns
+Decoded string of hex representation.
+
+#### Example
+```lua
+print(encoder.fromHex("6a6a6a")))
+```

mkdocs.yml

@@ -36,6 +36,7 @@ pages:
         - 'bthci':        'en/modules/bthci.md'
         - 'can':          'en/modules/can.md'
         - 'dht':          'en/modules/dht.md'
+        - 'encoder':      'en/modules/encoder.md'
         - 'file':         'en/modules/file.md'
         - 'gpio':         'en/modules/gpio.md'
         - 'i2c':          'en/modules/i2c.md'