The radio communication technology is the heart of the BigClown IoT Kit. This document describes the basic operation of the radio.
With BigClown, you can build your own network in the Sub-GHz band.
The radio frequency 868 MHz (for Europe) or 915 MHz (for the U.S.) allows long distance communication and offers low-power operation. Since this frequency band is used for signal messages, you will not encounter interference with streaming protocols like WiFi, Bluetooth, etc.
We have done several radio communication tests. We claim, that from a single point, you are typically able to provide a full-house radio coverage.
On the other hand, several factors influence the communication distance - the most important is the building material from which you have built your house, obstacles in the path, interference from other appliances, etc.
The only objective radio communication range measurement is a so-called line-of-sightdistance measured outdoor.
On the other hand, if the radio communication range is not sufficient, the network can be expanded on IP level thanks to MQTT message replication to a master server.
BigClown supports only star network topology. Such configuration offers high reliability, easy troubleshooting and deterministic service time from batteries.
There are two types of devices in the BigClown radio network:
There can be only one gateway device per network. The gateway device can be either:
BigClown Radio Dongle (it can handle up to 32 devices)
BigClown Core Module (it can handle up to 16 devices)
There can be one to several node devices in the network. Every node has to be paired to the gateway. A node device can be some sensor (e.g. temperature, humidity, CO2) or actuator (power relay, LCD display, LED strip controller).
Pairing process is very straightforward procedure:
This is done by cycling the power on the node device. On battery-operated node, you simple remove the batteries, wait a few seconds (to get the capacitors discharged) and insert the batteries back. The pairing request is sent on the boot.
Communication frequency (Europe)
Communication frequency (U.S.)
TX Frequency Deviation
TX Transmit Power
RX Filter Bandwidth
For parts of the world where the ISM band is 915 MHz, you cannot use default 868 MHz communication frequency. During the code compilation you have to pass
BAND parameter to the
make like this:
Right now it is not possible to use
bcf tool because all the firmwares are pre-compiled with 868 MHz band. Make sure you also compile Radio Dongle firmware with this parameter.
Explanation of the fields:
This part is called preamble and consists of alternating sequence of zeroes and ones (32 bits).
This part is called synchronization word and has a fixed value of
This part determines the length of the
DATA plus 1 (
DST field is also counted).
This is destination address (for logic network addressing).
Variable length payload data field.
Checksum calculated over all fields excluding
SYN fields. The polynomial of the CRC engine is