HomePublicationsPaper

Abstract Timers and their Implementation onto the ARM Cor tex-M family of MCUs
Ref: CISTER-TR-151202       Publication Date: 8, Oct, 2015

Abstract:
Real-Time For the Masses (RTFM) is a set of languages and to ols b eing develop ed to facilitate emb edded software development and provide highly efficient implementations geared to static verification. The RTFM-kernel is an architecture designed to provide highly efficient and predicable Stack Resource Policy based scheduling, targeting bare metal (singlecore) platforms. We contribute b eyond prior work by intro ducing a platform indep endent timer abstraction that relies on existing RTFM-kernel primitives. We develop two alternative implementations for the ARM Cortex-M family of MCUs: a generic implementation, using the ARM defined SysTick- /DWT hardware; and a target sp ecific implementation, using the match compare/free running timers. While sacrificing generality, the latter is more flexible and may reduce overall overhead. Invariants for correctness are presented, and metho ds to static and run-time verification are discussed. Overhead is b ound and characterized. In b oth cases the critical section from release time to dispatch is less than 2us on a 100MHz MCU. Queue and timer mechanisms are directly implemented in the RTFM-core language and can b e included in system-wide scheduling analysis.

Per Lindgren

,

Emil Fresk

,

Marcus Lindner

,

Andreas Lindner

,

David Pereira

,

Luis Miguel Pinho

Document:

View
PDF Download
PDF