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-sight distance measured outdoor.
We've achieved more than 500 meters line-of-sight communication range between two Core Modules.
Also the single USB Dongle / Core Module is enough to cover three-story house and whole garden around it.
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.
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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 USB 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:
The gateway device needs to be in the pairing mode.
The node device has to transmit the pairing request.
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.
Once all node devices are enrolled, you have to exit the pairing mode.
|Communication frequency (Europe)||868.0 MHz|
|Communication frequency (U.S.)||915.0 MHz|
|Modulation Rate||19.2 kbps|
|TX Frequency Deviation||20 kHz|
|TX Transmit Power||11.6 dBm|
|RX Filter Bandwidth||100 kHz|
+--------+--------+--------+--------+-------------+--------+ | PRE(4) | SYN(4) | LEN(1) | DST(1) | DATA(0..60) | CRC(2) | +--------+--------+--------+--------+-------------+--------+
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
DATAplus 1 (
DSTfield is also counted).
This is destination address (for logic network addressing).
Variable length payload data field.
Checksum calculated over all fields excluding
SYNfields. The polynomial of the CRC engine is