Amazon FreeRTOS Examples

This repo shows how to set up a CMake project for ESP32 and use amazon freertos as an external library.

See the official document for software prerequisite, https://docs.aws.amazon.com/freertos/latest/userguide/getting_started_espressif.html

Build instruction,

cmake -S . -B build -DCMAKE_TOOLCHAIN_FILE=freertos/tools/cmake/toolchains/xtensa-esp32.cmake -GNinja

To flash,

cmake --build build --target flash

To monitor the output,

export ESPPORT <replace-with-serial-port-of-ESP32>
amazon-freertos/vendors/espressif/esp-idf/tools/idf.py monitor

Troubleshooting

Linker Error: undefined reference to

If you changed some configuartion and run into this, usually it's because of missing dependent libraries/demos. To fix it, first find out which CMake target the missing functions belong to, normally it should be in the CMakeLists.txt closest to the source file where the functions are defined. Then add the CMake target to your application dependency list using the target_link_libraries command in the root level CMakeLists.txt. For example,

1. Linker complains about undefined reference to NumericComparisonInit.
2. NumericComparisonInit is defined in amazon-freertos/demos/ble/iot_ble_numericComparison.c.
3. amazon-freertos/demos/ble/CMakeLists.txt defines the target ble_numeric_comparison which has this source file.
4. Link AFR::demo_ble_numeric_comparison target with target_link_libraries to your application target. (demo_ prefix is added because it's a demo module, all target names can be found in the summary of CMake output)