Introduction to ZigBee Profiles
Within the ZigBee standard, specific data formats, referred to as ‘profiles,’ are defined. These profiles play a crucial role in ensuring interoperability among products manufactured by different companies. One of the initial data formats developed was the Home Controls-Lighting (HC-L) profile. Its primary objective is to facilitate the transmission of simple on/off messages. The fundamental purpose behind this profile is to eliminate the need for running extensive cables to wall-mounted light switches in various building applications.
Versatile Applications of HC-L Profile
Although the HC-L profile is primarily tailored for sending basic on/off messages in lighting control, its utility extends beyond this realm. It can be employed for a myriad of applications, such as integrating ZigBee remote control capabilities into diverse projects. A notable example of a commercially available product utilizing the HC-L profile is the Pixie Switcher from Flexipanel (www.flexipanel.com). This device functions as an HC-L switching module, featuring an integral antenna and supporting up to 8 switching control lines known as endpoints (EPs). In its input configuration, the Pixie Switcher monitors the endpoint voltage. Upon a state change, the device generates a corresponding message. All devices employing the HC-L profile support essential commands such as ‘on,’ ‘off,’ and ‘toggle.’
Setting Up Input and Output Correlation
When configured as an output, the digital output of an endpoint corresponds to the last received switching input message. Establishing a connection between input and output endpoints is managed through one-time setup procedures known as ‘joining and binding.’ Initially, upon power-up, a device seeks a ZigBee network to join. With appropriate security measures, any router node can permit the new node to become a part of the network.
Binding Inputs and Outputs
Once integrated into the network, the new node’s inputs and outputs need to be ‘bound’ to corresponding inputs and outputs on other nodes within the network. This binding process involves pressing the ‘bind’ button simultaneously on both devices. Remarkably, one input can control multiple outputs, and vice versa. For instance, a switch in a bedroom or hallway could potentially control all the lights in a house. The application circuit, as demonstrated in the schematics, showcases a Pixie Switcher unit configured with two inputs and two outputs.
Configuration and Circuit Integration
Prior to integrating the modules into the circuit, configuration is necessary using the RxD and TxD serial interface pins (not depicted). The transmitter, shown in Figure 1, operates in sleep mode and activates only when a button is pressed. It can be powered between 2.1 V and 3.3 V, allowing direct connection to two AA batteries.
Receiver Setup and Network Coordination
Figure 2 illustrates the receiver configuration. By setting ModeB high, it functions as a router, enabling battery-powered sleeping devices like the transmitter to join as neighbors. However, routers must remain operational continuously, making them unsuitable for battery power. ModeA, when set high, designates the router as a coordinator. A ZigBee network typically has one coordinator, which initiates a new network upon startup instead of seeking an existing one. Additional router nodes in this network would require the ModeA pin to be low. The receiver’s EP1 and EP2 are connected to relays through MOSFET driver transistors, allowing the relay contacts to integrate with various project circuits.