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DEVELOPMENT.md

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Development Instructions

Features

The teensy middleware framework provides build automation for middleware. This means that message dependencies are defined through a yaml file and build automatically.

The triggered hooks setup the udev rules and in the process you have to physically reconnect the device.

After the reboot the automatic boot loader invocation is triggered during the build process and no user intervention is required.

Custom Target

Adding your own target is simple

  • Create a target directory under firmware/targets/YourTargetName/
    • Add your directory to firmware/platformio.ini
    • Add config.yaml in your target directory (Defines your middleware repositories)
    • Note: See references for PlatformIO and SCons for usage and existing configurations in this repository.

Middleware

The build environment supports automated generation of message libraries. The message generation is defined in the config.yaml file accompanying the platformio.ini in the firmware/targets/PROJECTNAME directory.

The first build generates the necesseray libraries into firmware/external and will subsequently skip the rebuild if these directories exist. If no additional ROS message libraries besides the standard messages are desired, the only required key in config.yaml is PROJECTNAME: ros1: (see e.g. firmware/targets/example/config.yaml without example_msgs).

Note: The messages will not be re-downloaded and rebuilt unless the firmware/external/PROJECTNAME folder is first manualy deleted.

Currently there is only ROS1 support to generate middleware:

  • Build automation then generates message headers for serialisation and deserialisation based on your configuration.
  • In order to add automated build support for your own custom middleware message repositories it is recommend to create a lightweight message-only repository of the form project_msgs, which can be added to the ./targets/YourTargetName/config.yaml with the tags {ref,deploy_key}:
    • ref: Is the ssh link to the repository
    • deploy_key: Is only necessary for private repositories. (see note below)

Note: Optional for closed source repositories add the deploy_key: keyname (located in ./resources/deploy_keys/). Use ssh-keygen, then add the public key *.pub to the message repository and add the private key to the folder resources/deploy_keys. The key needs to be generated without a password. The .gitignore is by default ignoring all keys in resources/deploy_keys/. New keys need to be added with git add -f resources/deploy_keys/YourNewKey.

Teensy Hardware Specs

  • PJRC Teensy 4.0 ARM Cortex-M7 600MHz (NXP iMXRT1062 chip)
  • 2MB Flash
  • 1MB RAM (two banks)
    • RAM1 - 512KB : FASTRUN (ITCM, DTCM)
    • RAM2- 512KB : DMAMEM

Abbreviations

  • ITCM: instruction tightly coupled memory link - no chache, access predictable and each cycle
  • DTCM: data tightly coupled memory - see link above

References

  • ARM Cortex M7 Technical Reference link
  • tickless-mode: HW counter of physical timer - no system interrupts link
  • rosserial_arduino : getting started link(obsolete)
    • rosrun rosserial_arduino serial_node.py /dev/ttyACM0 : connect from workstation / desktop to embedded device
  • SCons software construction build utility tool API link
  • XRCE-DDS (NTP based time synchronization) link
  • YAML 3rd standard 1.2 - link (for middleware definition)