Flow

Flow is a tiny C++ wrapper around Atmel's lightweight mesh framework, featuring:

• A simple mesh network built on the 802.15.4 standard
• Low power
• 16 different endpoints (endpoints can be reserved for specific uses: e.g., sensor data, control, etc.)
• Listeners
• Non-blocking transmissions
• Strongly typed configuration and callback-oriented design

The library uses the Embedded Template Library to avoid use of the heap and have increased safe guards against buffer overflows.

The flow library exposes a mesh module which is the base for every mesh application. A convenience publisher module that builds on the functionality in the mesh module is provided. It forms the basis for a node that publishes at a regular interval and goes to sleep for the remaining time. The example application found in example/publisher uses the publisher module.

The example project found in example/base_station forms the basis for a base node that takes in the data published from the publisher and can relay them further or do some processing on the data.

Different types of nodes

When the mesh module is initialized, it takes in a configuration specifying, among other things, the address of the node in the mesh network. The following specification is used for the addresses:

• 0x0000-0x7FFF: Routers (coordinators or relays)
• 0x8000-0xFFFF: End-devices

This makes it possible to construct a chain on the following way:

+------------------------+
|      Base Station      |
|        (0x0000)        |
+-----------+------------+
            |
            |
+-----------+------------+
|         Relay          |
|       (0x0001)         |
+----------+-------------+
      |           |     
      |           |     
+-----+----+  +----+-----+
| Device 1 |  | Device 2 |
| (0x8001) |  | (0x8002) |
+----------+  +----------+

Supported boards

Board	MCU	Image
ATmega256RFR2 Xplained Pro	ATmega256RFR2
ATZB-X-233-USB	ATxmega256A3U
ATZB-X-233-XPRO	ATxmega256A3U
ATZB-256RFR2-XPRO	ATmega256RFR2

Repository Structure

• src: Contains the C++ wrapper layer and a CMake port of the required ASF drivers as well as the lightweight mesh framework
• cmake: Cmake modules for toolchains and the library
• examples: Example applications

Setup

Requirements:

• avr-gcc
• CMake
• avrdude
• Optional: dfu-programmer (for the ATZB-X-233 USB kit)

To get started, look at the examples in the examples folder. An env file can be used to not expose security keys, channels, PAN ID etc. in source control. An example env file is in the root of the examples folder. The file is on the following format:

_SECURITY_KEY=MySecurityKey
_APP_PANID=0x1234
_APP_CHANNEL=0x01

Note: The maximum length of the security key is 16 bytes. A key longer than this will be clamped to 16 bytes.

1. Navigate to an example in the examples folder
2. mkdir build && cd build && cmake .. && make -j
3. make flash

The default CMake target is release. To build for debug, use cmake -DCMAKE_BUILD_TYPE=Debug .. && make -j. The preprocessor directive MESH_ENABLE_LOGGING dictates whether logging is enabled or not for the internal functionality in the mesh library.

Getting started with a new application

The examples provided in the examples folder provides a starting point for new applications and can be used as a reference for new applications. The convenience publisher module also forms a starting point for a more complex application with a state machine.