User Guide

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Operation with the HumPRO
TM
Series
The commands from the HumPRC
TM
Series module can be received by
a HumPRO
TM
Series transceiver and vice versa. The modules should be
joined using the normal Join Process. The IU sends a REMOTE_ACTIVATE
packet and accepts a REMOTE_CONFIRM reply.
A microcontroller connected to the HumPRO
TM
Series can be programmed
to take action based on the STATUS byte in a REMOTE_ACTIVATE packet
that is received from a HumPRC
TM
Series module. It can also read out the
packet header and know the address of the sending module and respond
with a REMOTE_CONFIRM packet to activate the ACK_OUT line on the
HumPRC
TM
module.
Likewise, the microcontroller can be programmed to send a REMOTE_
ACTIVATE packet to a HumPRC
TM
Series module. This opens up many
options for creative mixed-mode design.
Remote Activation
The REMOTE_ACTIVATE packet consists of six bytes:
0x03 0x00 0x00 0x00 0x10 <STATUS>
The first byte is 0x03 with the next three bytes 0x00. Byte five is 0x10
which indicates a Remote Activation. Byte six is the STATUS byte, which is
a bit map of the status line states. Bit 0 corresponds to status line S0 and
so forth. Each bit is 1 if the corresponding line is high.
Remote Confirm
The REMOTE_CONFIRM packet has the following format:
0x03 0x00 0x00 0x00 0x11 <DURATION> <ALIVE>
The first byte is 0x03 with the next three bytes 0x00. Byte five is 0x11 and
indicates that the packet is a remote confirm packet.
The DURATION byte indicates the amount of time that the ACK_OUT line
should be held high. This value is multiplied by 10ms. If the value is 0, the
output is immediately taken low. The default value is 0x02 for 20ms. This
value overrides the effect of a previously received REMOTE_CONFIRM
packet.
The ALIVE byte indicates how long after the transmission the IU module
should stay awake in receive mode. This value is multiplied by 0.1s. Once
this duration expires, the module returns to sleep mode.
This message is transmitted to the IU’s address. It must be received by the
IU within one second of initial transmission or within the ALIVE interval of
the previous REMOTE_CONFIRM packet.
Carrier Sense Multiple Access (CSMA)
CSMA is an optional feature. It is a best-effort delivery system that listens
to the channel before transmitting a message. If CSMA is enabled and
the module detects another transmitter on the same channel, it waits until
the active transmitter finishes before sending its payload. This helps to
eliminate RF message corruption and make channel use more efficient.
When a module has data ready to transmit and CSMA is enabled, it listens
on the intended transmit channel for activity. If no signal is detected,
transmission is started.
If a carrier is detected with an RSSI above the CSMA threshold in the
CSRSSI register, transmission is inhibited. If a signal below the threshold is
detected that has a compatible preamble or packet structure, transmission
is also inhibited.
If the module is synchronized from a recent packet transfer, it waits for a
random interval, then checks again for activity. If the detected carrier lasts
longer than the time allowed for the current channel, the module hops to
the next channel in the hop sequence and again waits for a clear channel
before transmitting.
If the module is not synchronized, it hops to the next channel and again
checks for interference. When no activity is detected it starts transmitting.
This feature is disabled by default in the HumPRC
TM
so that the fastest
response time is obtained. Enabling it can impact transmission timing, so
care should be taken with its use.