Memfault FreeRTOS Demo Application

This example demonstrates integrating Memfault with FreeRTOS applications. The example uses the QEMU target, MPS2 Cortex M3 AN385, to run the application and is based on the MPS2 Cortex M3 AN385 FreeRTOS Demo. This file outlines various components of the example application. For more information on the MCU SDK, please see our documentation at docs.memfault.com.

Prerequisites

The project requires the following:

  • git
  • GNU Make
  • A version of the Arm GNU Toolchain
    • Note: The project assumes the toolchain can be found via your environment's PATH, otherwise you may specify by setting ARM_CC with the full path to the toolchain /bin directory

FreeRTOS Installation

By default the project will clone FreeRTOS V11.2.0 into the project directory. If you would like to use a different version, please set FREERTOS_DIR to an existing FreeRTOS directory.

Building

To build, from the project directory run:

make

Running

To run, from the project directory run:

make run

With the console open you may test out various features using the demo CLI commands. A simple example of testing assert handling and data export:

MFLT:[INFO] GNU Build ID: 8a45620abae6842848670c379411d8b31846eadc
MFLT:[INFO] S/N: freertos-example
MFLT:[INFO] SW type: qemu-app
MFLT:[INFO] SW version: 1.0.0
MFLT:[INFO] HW version: qemu-mps2-an385
MFLT:[INFO] Memfault Initialized!

mflt> test_assert
MFLT:[INFO] GNU Build ID: 8a45620abae6842848670c379411d8b31846eadc
MFLT:[INFO] S/N: freertos-example
MFLT:[INFO] SW type: qemu-app
MFLT:[INFO] SW version: 1.0.0
MFLT:[INFO] HW version: qemu-mps2-an385
MFLT:[INFO] Memfault Initialized!

mflt> export
MFLT:[INFO] MC:SK8SgQlDT1JFAgYAAwwTFAABTAYAIwGAAAD//wAAe30AAEBmACB7fQwACKUHgFMAICilE3BTACA3WAAAhG8KABNhMP8/IHBTACAMDgABFAY=:
MFLT:[INFO] MC:wE0AKYpFYgq65oQoSGcMN5QR2LMYRurcAg4AARAGACFmcmVlcnRvcy1leGFtcGxlCg4AAQUGAAsxLjAuMAsOAAEIBgARcWVtdS1hcHAEDgA=:
MFLT:[INFO] MC:wJsBAQ8GAB9xZW11LW1wczItYW4zODUHDgABBAYAASgGAAEFDgABBAYACQGAAAABBgAJJO0A4BwSAAEBCAABQCAAAQEGAAkY7QDgDBoABP8=:
MFLT:[INFO] MC:wOgBAQEGAAkE4ADgEB4ACQcAAQABBgAJBO0A4AgGAAcD+AAECAABAQYACfztAOAEDgABAQgAB+EA4AQOAAEBCAAH4gDgBA4AAQEIAAfjAOA=:
MFLT:[INFO] MC:wLUCBA4AAQEIAAfkAOAgRgABAQYACUhlACAoBgAGARoAAakIACcCAADMWQAgzFkAIAACAABpvQAAAQYA4QLMWQAgAAIAAAE2R05VIEJ1aWw=:
# Output clipped

The exported output can be pasted into the Memfault web app for processing. See this page in our docs.

Debugging

To debug, from the project directory run:

make debug

QEMU will start the application and wait for a debugger to attach. From a separate terminal run:

make gdb

Application Features

Console and Memfault Demo CLI

The application is built with the MCU SDK‘s demo CLI. This CLI includes commands to trigger faults; collect data from logs, trace events, and metrics; and export data to Memfault’s web application for processing. For more info on the commands available use the “help” command in the console or view the source code at memfault-firmware-sdk/components/demo.

Application Metrics

Two simple tasks are used to illustrate creating metrics to measure your application's performance. The first task, Heap Task, allocates and deallocates memory periodically. A second tasks, Metrics Task, sets metrics based on the state of the system heap. The two metrics produced are:

  • FreeRTOS_HeapFreeBytes: Measures current total bytes free in the FreeRTOS heap
  • FreeRTOS_HeapMinFreeBytes: Measures the lowest total bytes free in the FreeRTOS heap since boot
  • FreeRTOS_Heap_pct_max: Measures the max percentage of the FreeRTOS heap used since boot

These metrics are collected every 60 seconds in this example. This can be changed by modifying MEMFAULT_METRICS_HEARTBEAT_INTERVAL_SECS in memfault_platform_config.h.

Heap Tracing

The heap tracing capabilities of the MCU SDK are enabled by default. The SDK will collect a set of the most recent allocations with their location in code and size when a coredump is saved.

Logging Collection

The application is configured to collect the most recent logs along whenever a coredump is collected.