> For the complete documentation index, see [llms.txt](https://cavedu.gitbook.io/linkit-7697/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://cavedu.gitbook.io/linkit-7697/linkit-7697-development-guide-for-arduino-ide/developer-guide/using-mcs-library/mcs-library-api-reference/mcsdatachannel-classes.md).
# MCSDataChannel Classes
The following classes extend MCSDataChannel, which is used to create a **data channel** instance mapping to the one created on the MCS server and provide operations on a data channel, including getting and uploading data points.
For example, an ON/OFF controller channel shown below:
This channel can be represented by an instance of the class **MCSControllerOnOff**, as shown below:
```
MCSControllerOnOff channelOnOff("channel_id_1");
device.addChannel(channelOnOff); // device is an instance of MCSDevice or MCSLiteDevice.
device.connect();
bool controllerValue = channel.value();
```
Data channel classes provide **set()** and **value()** methods for each data channel as they have different formats. Use the following extended classes in your sketch to create a specific type of data channels.
There are 2 major sub-class categories, **controller channel** and **display channel**. Controller channels, such as MCSController*OnOff* and MCSController*Integer*, represents controller channels on MCS. Display channels such as MCSDisplay*Float* and MCSDisplay*String* maps to display channels instead.
### Constructors
MCSDataChannel()
{% tabs %}
{% tab title="MCSDataChannel()" %}
Creates a *data channel* that can be added to a *device* that is an instance of MCSDevice or MCSLiteDevice.
**Syntax**
MCSControllerOnOff *dataChannel*(data\_channel\_ID)
MCSDisplayOnOff *dataChannel*(data\_channel\_ID)
MCSControllerCategory *dataChannel*(data\_channel\_ID)
MCSDisplayCategory *dataChannel*(data\_channel\_ID)
MCSControllerInteger *dataChannel*(data\_channel\_ID)
MCSDisplayInteger *dataChannel*(data\_channel\_ID)
MCSControllerFloat *dataChannel*(data\_channel\_ID)
MCSDisplayFloat *dataChannel*(data\_channel\_ID)
MCSControllerHex *dataChannel*(data\_channel\_ID)
MCSDisplayHex *dataChannel*(data\_channel\_ID)
MCSControllerString *dataChannel*(data\_channel\_ID)
MCSDisplayString *dataChannel*(data\_channel\_ID)
MCSControllerGPS *dataChannel*(data\_channel\_ID)
MCSDisplayGPS *dataChannel*(data\_channel\_ID)
MCSControllerGPIO *dataChannel*(data\_channel\_ID)
MCSDisplayGPIO *dataChannel*(data\_channel\_ID)
MCSControllerPWM *dataChannel*(data\_channel\_ID)
MCSDisplayPWM *dataChannel*(data\_channel\_ID)
MCSControllerAnalog *dataChannel*(data\_channel\_ID)
**Parameters**
data\_channel\_ID: The data channel id of the data channel you created on MCS.
**Returns**
*dataChannel* is an instance of the subclass of the **MCSDataChannel** class.
{% endtab %}
{% endtabs %}
### MCSDataChannel Methods
For each type of data channel:
updated()
valid()
value()
{% tabs %}
{% tab title="updated()" %}
To check if there is updated data point received for a specified data channel. To check if channels are updated, users must call *device.*process() first, which checks if there any incoming command update from MCS server. If there are multiple updated values happened, only the last value will be kept.
**Syntax**
*dataChannel*.updated()
**Parameters**
none
**Returns**
boolean true if there is an updated data point received for this data channel, false if there isn't.
{% endtab %}
{% tab title="valid()" %}
To check if there is valid value received or set from a specified data channel.
**Syntax**
dataChannel.valid()
**Parameters**
none
**Returns**
boolean true if there is a valid value received or set for this data channel, false if there isn't.
{% endtab %}
{% tab title="value()" %}
To get the current value of a specified data channel except MCSControllerGPS and MCSDisplayGPS.
**Syntax**
*dataChannel*.value()
**Parameters**
none
**Returns**
The value of specified data channel and the data type of value is based on data channel, including float, integer long or string.
{% endtab %}
{% endtabs %}
### Display Channel Methods
set()
{% tabs %}
{% tab title="set()" %}
To set the value to a specified display data channel.
**Syntax**
dataChannel.set(value)
MCSDisplayPWM.set(value, period)
MCSDisplayGPS.set(latitude, longitude, altitude)
**Parameters**
dataChannel: an instance of the MCSDataChannel extended classes, like MCSControllerOnOff, MCSControllerCategory...
MCSDisplayPWM: an instance of MCSDisplayPWM class
MCSDisplayGPS: an instance of MCSDisplayGPS class
value: the value you are going to set for a specified data channel and the data type of value is various according to data channel, like float, integer, long or string.
period: a specific integer parameter for PWM type of data channel. This period is the inverse of the PWM frequency.
latitude, longitude, altitude: specific float parameters for GPS type of data channel to present the GPS coordinate.
**Returns**
boolean true if the value is set and uploaded to MCS server successfully, false if it fails.
{% endtab %}
{% endtabs %}
### Controller Channel Methods
setServerValue()
{% tabs %}
{% tab title="setServerValue()" %}
To set the value to a specified display data channel.
**Syntax**
controllerChannel.setServerValue(value)
**Parameters**
dataChannel: an instance of the MCSDataChannel extended classes, like MCSControllerOnOff, MCSControllerCategory...
| Channel Class | Value Type |
| --------------------- | ----------- |
| MCSControllerOnOff | bool |
| MCSControllerFloat | float |
| MCSControllerInteger | int |
| MCSControllerAnalog | int |
| MCSControllerGPIO | int |
| MCSControllerHex | long |
| MCSControllerCategory | String |
| MCSControllerString | String |
| MCSControllerPWM | MCSPWMValue |
| MCSControllerGPS | MCSGPSValue |
latitude, longitude, altitude: specific float parameters for GPS type of data channel to present the GPS coordinate.
**Returns**
boolean true if the value is set and uploaded to MCS server successfully, false if it fails.
{% endtab %}
{% endtabs %}
### MCSControllerPWM Methods
For **PWM controller** data channel, we provide
dutyCycle()
period()
{% tabs %}
{% tab title="dutyCycle()" %}
To get the current dutyCycle(value) setting of a specified PWM controller data channel.
**Syntax**
MCSControllerPWM.dutyCycle()
**Parameters**
MCSControllerPWM: an instance of MCSControllerPWM class
**Returns**
The duty cycle setting of specified PWM controller data channel (labeled as "value" in MCS UI) and the data type is integer.
{% endtab %}
{% tab title="period()" %}
To get the current period setting of a specified PWM controller data channel.
**Syntax**
MCSControllerPWM.period()
**Parameters**
MCSControllerPWM: an instance of MCSControllerPWM class
**Returns**
The period setting of specified PWM controller data channel and the data type is integer.
{% endtab %}
{% endtabs %}
### GPS Channel Methods
For **GPS controller** and **GPS display** data channel, we provide additional helper functions to parse the latitude, longitude and altitude fields.
latitude()
longitude()
altitude()
{% tabs %}
{% tab title="latitude()" %}
To get the current value of latitude of a specified GPS controller data channel.
**Syntax**
MCSControllerGPS.latitude()
**Parameters**
MCSControllerGPS: an instance of MCSControllerGPS class
**Returns**
The latitude of specified GPS controller data channel and the data type is float.
{% endtab %}
{% tab title="longitude() " %}
To get the current value of longitude of a specified GPS controller data channel.
**Syntax**
MCSControllerGPS.longitude()
**Parameters**
MCSControllerGPS: an instance of MCSControllerGPS class
**Returns**
The longitude of specified GPS controller data channel and the data type is float.
{% endtab %}
{% tab title="altitude()" %}
To get the current value of altitude of a specified GPS controller data channel.
**Syntax**
MCSControllerGPS.altitude()
**Parameters**
MCSControllerGPS: an instance of MCSControllerGPS class
**Returns**
The altitude of specified GPS controller data channel and the data type is float.
{% endtab %}
{% endtabs %}
### Gamepad Controller Channel Methods
A **Gamepad** controller channel's value is an event with two fields:
* which button(**BTN\_UP, BTN\_DOWN, BTN\_LEFT, BTN\_RIGHT, BTN\_A, BTN\_B**) is pressed or released.
* The event is a **BTN\_PRESSED** event or a **BTN\_RELEASED** event.
The buttons are represented by the enumeration below:
```
enum MCSGamePadButton{
BTN_UP = 1,
BTN_DOWN,
BTN_LEFT,
BTN_RIGHT,
BTN_A,
BTN_B,
BTN_INVALID
};
```
and the events are represented by another enumeration:
```
enum MCSGamePadButtonEvent{
BTN_PRESSED = 1,
BTN_RELEASED = 0,
BTN_NO_EVENT = -1
};
```
So the object returned by the value() method can be read by accessing these two fields:
```
if(BTN_UP == gamepadChannel.value().button &&
BTN_PRESSED == gamepadChannel.value().event)
{
// Do something when the "UP" key is pressed...
}
```
Following helper methods are also provided to easily access the button and event fields:
button()
event()
{% tabs %}
{% tab title="button() " %}
Returns a MCSGamePadButton enumeration representing the buttons being pressed or released
**Syntax**
MCSControllerGamePad.button()
**Parameters**
MCSControllerGamePad: an instance of MCSControllerGamePad class
**Returns**
Returns a **MCSGamePadButton** enumeration representing the buttons being pressed or released. The possible values are:
```
enum MCSGamePadButton{
BTN_UP = 1,
BTN_DOWN,
BTN_LEFT,
BTN_RIGHT,
BTN_A,
BTN_B,
BTN_INVALID
};
```
{% endtab %}
{% tab title="event()" %}
Returns a MCSGamePadButtonEvent that denote a key pressed or key released event.
**Syntax**
MCSControllerGamePad.button()
**Parameters**
MCSControllerGamePad: an instance of MCSControllerGamePad class
**Returns**
Returns a **MCSGamePadButtonEvent** enumeration representing a pressed or released event. The possible values are:
```
enum MCSGamePadButtonEvent{
BTN_PRESSED = 1,
BTN_RELEASED = 0,
BTN_NO_EVENT = -1
};
```
{% endtab %}
{% endtabs %}