Library, build system and examples for three flavours of reactive intermittent computing:

• QuickRecall
• AllocatedState
• ManagedState

QuickRecall is the simplest method, where all data resides in non-volatile memory (FRAM). When a power failure is detected, the device saves CPU registers and sleeps. Although simple, this method results in very high power consumption during on-periods, because accesses to FRAM are far more expensive than those to SRAM.

AllocatedState allocates data to SRAM to lower power consumption, and must therefore load the .data and .bss sections, as well as the stack, from FRAM to SRAM during boot, and likewise save them to FRAM when power fails. Although improving power consumption during the on-period, loading and saving the entire allocated state can get quite expensive.

ManagedState improves on AllocatedState by tracking active and modified pages of memory, so that only active pages need to be loaded during boot, and only modified pages need to be saved when power fails. This can substantially reduce energy consumption and thereby improve performance over the two other methods.

ManagedState was presented in an academic paper,

"Efficient State Retention through Paged Memory Management for Reactive Transient Computing",
Sivert T. Sliper, Domenico Balsamo, Nikos Nikoleris, William Wang, Alex S. Weddell and Geoff V. Merrett,
IEEE Design Automation Conference (DAC 56), Las Vegas, 2019

available at DOI 10.1145/3316781.3317812.

Currently, ICLIB supports the MSPFR5994 platform, and can readily be ported to other MSP430-based platforms. Support for Arm Cortex-M0 targets is under development.

The following dependencies are needed to build ICLIB:

• cmake
• MSP 430 GCC toolchain (tested with msp430-gcc-7.3.1.24_linux64.tar.bz2)
• MSP430 support files
• (optional) mspdebug
  • Extract libmsp430.so from the MSP430 Debug stack to e.g. /usr/lib

Set environment variables MSP430_GCC_ROOT, that points to the toolchain directory, and MSP430_INC that points to the support file directory. This is done by e.g. adding the following two lines to your ~/.bashrc:

export MSP430_GCC_ROOT=<path/to/MSP430 GCC folder>
export MSP430_INC=<path/to/MSP430 support files>

ICLIB is built using CMAKE. To build an application make a build directory, and call CMAKE with options to set the target platform.

cd iclib
mkdir build
cd build
cmake .. -DTARGET_ARCH=msp430

By default, CMAKE is set up to do a debug build, for benchmarking you should run the release build:

cmake .. -DTARGET_ARCH=msp430 -DCMAKE_BUILD_TYPE=Release

Then build an executable, for example aes using ManagedState:

make aes-MS-msp430

The syntax here is <app-icmethod-target>, where QR selects QuickRecall, AS selects AllocatedState, and MS selects ManagedState.

Finally, on supported platforms, you can upload the executable to the microcontroller using

make upload_aes-MS-msp430

Note that this uses mspdebug, and will only work on some setups (only tested on a laptop running Ubuntu 18.04).