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HPSC RTEMS Applications

This project contains RTEMS libraries and applications for the HPSC Chiplet. Applications are for the TRCH (Cortex-M4) and RTPS (Cortex-R52) subsystems.

Common code includes drivers, library routines, and platform configurations. The project layout is:

  • lib: top-level directory for libraries
    • drivers: produces libhpsc-drivers.a containing low-level driver code. This code must not have dependencies on anything else in this project. Ideally, this code can be merged into upstream RTEMS.
    • drivers-selftest: produces libhpsc-drivers-selftest.a. These library routines accept parameters for testing drivers and hardware. This library may only depend on libhpsc-drivers.
    • hpsc: produces libhpsc.a containing common library routines. This library may only depend on libhpsc-drivers.
    • hpsc-test: produces libhpsc-test.a containing tests for libhpsc. This library may only depend on libhpsc.
  • plat: shared platform configurations to be used by applications.
  • rtps-r52: produces rtps-r52.img containing the reference/test RTEMS application for the R52s in the RTPS subsystem.
  • trch: placeholder for a future reference/test RTEMS application for the TMR M4Fs in the TRCH subsystem.

As a general rule of thumb, libraries should be independent of the RTEMS BSP, HPSC platform, and application (e.g., rtps-r52) configuration. This includes the creation of RTEMS tasks -- create tasks in the application and pass task IDs to library routines to start/use when needed.

Building

To compile, first add the RTEMS Source Builder bin directory to PATH. For example, if the --prefix used was /opt/hpsc/RSB-5/, then:

export PATH=/opt/hpsc/RSB-5/bin:$PATH

Then set RTEMS_MAKEFILE_PATH to be of the form <prefix>/<target>/<bsp>. The prefix depends on your install location. The target should be arm-rtems5. The bsp should be gen_r52_qemu (no option for M4 yet).

For example:

export RTEMS_MAKEFILE_PATH=/opt/hpsc/RTEMS-5-RTPS-R52/arm-rtems5/gen_r52_qemu

Then finally:

make

Optionally install the libraries, headers, and applications with:

make install

For each library libfoo (not a real library), the static lib is installed to ${PROJECT_RELEASE}/lib/libfoo.a and its headers to ${PROJECT_RELEASE}/lib/libfoo/. PROJECT_RELEASE is configured by the Makefile at RTEMS_MAKEFILE_PATH, and may be the same value. Out-of-tree libraries and applications may include these headers and link against the libraries produced by this project (described above).

Applications are installed to ${PROJECT_BIN}.

Drivers

Current drivers are:

  • hpsc-mbox: HPSC Mailbox
  • hpsc-rti-timer: HPSC Real-Time Interrupt Timers
  • hpsc-wdt: HPSC Watchdog Timers (now in RTEMS BSP)

Library Code

Current library tools are:

  • affinity: A simple wrapper around RTEMS CPU affinity implementation.
  • command: A framework for command processing.
  • devices: A common location to store dynamic devices for easy access.
  • hpsc-msg: Utility functions for constructing HPSC messages.
  • link: A two-way messaging channel that abstracts the exchange mechanism.
    • link-mbox: An implementation of link using HPSC Mailboxes.
    • link-shmem: An implementation of link using shared memory.
    • link-store: A common location to store open links for easy access.
  • shmem: A shared memory messaging interface, compatible with HPSC messages.
    • shmem-poll: Tasks to poll shared memory for HPSC message statuses and issue callbacks which mimic ISRs.
  • watchdog-cpu: A common watchdog kicker task.

Developer Notes

A few lessons learned for getting started with RTEMS:

  • Building
    • The RTEMS build system uses only directory and leaf Makefiles - mixing them is problematic.
    • The template Makefiles provided by RTEMS are a good starting point. They don't manage dependencies for incremental builds particularly well (e.g., on libraries, headers, and the Makefile itself) and must be extended.
    • See: https://devel.rtems.org/wiki/Developer/Makefile.
  • Interrupt Handling
    • You may NOT use printf in an interrupt context - you will not receive an error, things just won't work! Use printk instead.
    • RTEMS documentation does not currently describe more advanced interrupt handler functionality like rtems_interrupt_handler_install/rtems_interrupt_handler_remove.
    • See: https://docs.rtems.org/branches/master/c-user/interrupt_manager.html and refer to our existing drivers.
  • Testing
    • Keep test routines in separate libraries when possible. Applications may opt to not link against test code when unneeded.
    • Tests should be reusable across applications with only minor configuration (given as parameters).
    • It may be reasonable to exclude test libraries from the task creation rule. This couples them more tightly with the BSP and application configuration, but they should still be independent of platform configuration. This exclusion is strictly for convenience.

See https://docs.rtems.org for more help.