Linx Technologies HUM-xxx-RC - Manual (Page 13)

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Transceiver Operation
The transceiver has two modes of operation: Initiating Unit (IU) that
transmits control messages and Responding Unit (RU) that receives control
messages. If all of the status lines are set as inputs, then the module is set
as an IU only. The module stays in a low power sleep mode until a status
line goes high, starting the Transmit Operation.
If all of the status lines are set as outputs, then the module is set as an RU
only. It stays in Receive Operation looking for a valid transmission from a
paired IU.
A module with both input and output status lines can operate as an IU
and an RU. The module idles in Receive Operation until either a valid
transmission is received or a status line input goes high, initiating the
Transmit operation.
When an input goes high, the transceiver captures the logic state of each
of the status lines. The line states are placed into a packet along with the
local 32-bit address. The IU transmits the control packets as it hops among
25 RF channels.
An RU receives the packet and checks its Paired Module List to see if the
IU has been paired with the module and is authorized to control it. If the
IU’s address is not in the table, then the RU ignores the transmission. If
the address is in the table, then the RU calculates the channel hopping
pattern from the IU’s address and sets its status line outputs according to
the received packet. It then hops along with the IU and updates the states
of its outputs with every packet. Its outputs can be connected to external
circuitry that activates when the lines go high.
The RU can also send an acknowledgement back to the IU. Using the
serial interface the RU can include up to two bytes of custom data with
the acknowledgement, such as sensor data or battery voltage levels.
Using the hardware control, if ACK_EN is high when a valid control packet
is received, the RU sends back a simple acknowledgement (ACK). It can
send an Acknowledge with Data (AWD) response when custom data is
programmed into the module using a serial command.
Transmit Operation
Transmit operation can be started by a status line input going high or a
serial command.
Basic remote control applications use the status line activation. The module
pulls the MODE_IND line high and repeatedly transmits control messages
containing the local address and the state of all status lines. Between
transmissions the module listens for acknowledgement messages. If an
Acknowledge (ACK) or Acknowledge with Data (AWD) message is received
for the transmitted data, the ACK_OUT line is asserted for 100ms. The
ACK_OUT timing restarts on each ACK or AWD packet that is received.
The transceiver sends control messages every 13.33ms as long as
any of the status line inputs is high, updating the status line states with
each packet. When all input lines are low, the module starts the shutoff
sequence.
During the shutoff sequence, the transmitter sends at least one packet with
all outputs off. It then continues to transmit data until the current channel
hopping cycle is complete, resulting in balanced channel use. If an input
line is asserted during the shutoff sequence, the transmitter cancels the
shutoff and extends the transmission sequence.
The Transmit Control Data and Transmit IU Packet serial commands
instruct the module to send control messages. The Transmit Control Data
command is the serial command version of taking a status line input high.
An external microcontroller can use this command to send a specified
number of packets with a specified Status byte rather than taking status
lines high.
The Transmit IU Packet command sends a packet that causes the
RU to respond with a packet that can include the readings of its two
analog inputs. This is good for reading remote sensors without having a
microcontroller on the sensor unit. This reduces the cost and development
time for remote sensor units.
The trigger configuration causes the module to send a pre-specified
number of packets when a status line input goes high. This is good for
remote monitoring and transmitting when an exception occurs without
needing a microcontroller on the remote unit.