MiraMesh on FreeRTOS examples

Current supported hardware is nrf52840, tested on nrf52840-dk.

Install

Download and unpack mira to src/vendor/libmira. Link should be provided from when getting your license.

Download and unpack nrf5-sdk, and place in src/vendor/nrf5-sdk. nrf5-sdk can be downloaded from Nordic Semiconductor. Preferred version for MiraOS. Current supported version is 17.1.0. Note, the original directory has a name similar to nRF5_SDK_17.1.0_ddde560 and has to be renamed.

Some dependencies are referred to as git submodules. Install them using: git submodule update --init --recursive

Those are:

• tinyprintf by CJlano
• FreeRTOS-Kernel

Compilation

All examples are built by running make in the top level directory

The build artifacts will be outputted as examplename-nrf52840.hex in top level directory.

All intermediate files will be placed in build/

To build a specific example, for example uart_tx, type make uart_tx-nrf52840.hex

For networking, there are three examples:

• net_rx - Acts as root node. run one per network
• net_tx - A mesh node, that sends packets to net_rx
• net_tx_with_ble - Same as net_tx, but is running concurrent BLE

Flashing

First, add a license to the device on address 0xff000 of length 0x1000, according to MiraOS documentation:

https://docs.lumenrad.io/miraos/2.7.2/description/licensing/licensing_tool.html#signing-a-connected-device

...or by flashing the license as a hex file if available.

Second, flash the softdevice to the device:

nrfjprog -f nrf52 --program src/vendor/nrf5-sdk/components/softdevice/s140/hex/s140_nrf52_7.2.0_softdevice.hex --sectorerase --verify

Then flash the application, for example:

nrfjprog -f nrf52 --program uart_tx-nrf52840.hex --sectorerase --verify

Examples

Examples can be found as directories under src/, except src/lib/ and `src/vendor/, which is common files used by all examples

Makefile specifying content of the builds can be found in make/targets/

UART TX

src/uart_tx/ is a bare minimum example to show the boilerplate of FreeRTOS and MiraMesh integration, running no network

Network Sender / Network Receiver

src/network_sender/ and src/network_receiver/ shows a pair firmwares where network receiver runs as root and can receieve packets from multiple network senders.

BLE example

src/ble_example/ shows how to integrate with concurrent BLE using nordics softdevice.

Version compatibility

Tested on agains Mira version 2.7.2, but should work with earlier versions too.

Timers

FreeRTOS needs a tick timer for task switching. Currently there are three modes available:

• SysTick
• RTC
• MiraMesh

Beside that, FreeRTOS can run in a mode called "Tickless", which can disable the ticks when no tasks are active, and compensate upon next wakeup. Tickless is necessary to reduce power consumption for running battery powered. Tickless however adds complexity during development, and may be

SysTick

Uses the SysTick handler in the ARM core. No nRF peripherals will be used for this mode.

RTC

Uses the nRF RTC peripheral directly, to provide a steady callback for ticks. This mode takes up one RTC peripheral. To use this mode, it is required to make sure that peripherals are available.

MiraMesh timer

Uses MiraMesh internal timers to provide a ticksource. The timer needs to be running anyway when using MiraMesh. Internally uses an nRF RTC, but is then shared with MiraMesh. Note that miramesh_init() has to be called before starting FreeRTOS scheduler. Also note that mira_net_init() doesn't have to be called for timer to run.

Memory allocation

MiraMesh allocates memory upon startup, including when calling mira_net_init() and other init functions. It however shouldn't allocate memory during runtime.

Same can apply to FreeRTOS. So using the same memory manager is suitable.

For that reason, MiraMesh memory management is therefore remapped to use FreeRTOS, using mira_mem_set_alloc_callback() to replace the internal MiraMesh allocation functions.