pyenergy

An interface to the MAGEEC energy monitor boards

Project description

This package contains two modules, pyenergy and platformrun. The first is a module which directly interfaces with the MAGEEC energy monitor boards, allowing measurements to be taken and the boards to be scripted. The second module, platformrun, allows easy measurement of binaries on platforms that can be measured with the boards. The procedure for running a binary is different for each boards, so module wraps the platforms in a consistent way.

The source code is available at https://github.com/jpallister/stm32f4-energy-monitor/ under the LGPL.

Getting started

The commands that need to be run to just run a binary on a platform:

$ energytool setup

This command will prompt you for the setup of the energy measurement devices that are attached to the computer.

$ platformrun-detect

This will detect whether the required tools are installed to run on the target platform. The -p flag prompts for locations of binaries, if they are in non standard places.

$ platformrun PLATFORM BINARY

This command runs the binary on the platform, recording energy measurements.

Pyenergy

This python module can be used in two ways, to script the energy monitor, and to configure the energy monitoring boards. This module is used by platformrun to communicate with the energy monitor, and implements commands such as setting up the energy monitoring, as well as pin triggering.

The energytool is also exposed by this module, allowing commandline access to the energy monitors.

$ energytool -h

Energy tools

Usage:
    energytool (-m MPOINT)... [options] read SERIAL PIN
    energytool (-m MPOINT)... [options] continuous SERIAL
    energytool (-m MPOINT)... [options] debug SERIAL
    energytool list
    energytool setup
    energytool changeserial SERIAL NEWSERIAL
    energytool interactive

Commands:
    read            This sets up a trigger on the specified PIN and waits for
                    an energy measurement.

    continuous      Continuously read measurements from the specified energy
                    monitor.

    debug           Output some debug data about the instantaneous voltages
                    seen on the ADCs, along with current and voltage.

    list            Show the serial numbers and API version of each connected
                    energy monitor.

    changeserial    Connect to the device specified by SERIAL, and change the
                    serial to NEWSERIAL

Scripting

The module exposes one class, EnergyMonitor. This class can be instantiated as such:

em = pyenergy.EnergyMonitor("EE00")

This connects to an energy monitor board with the serial EE00. Up to three of the four measurement points can then be enabled:

em.enableMeasurementPoint(1)

Measurement can be started and stopped in a similar way:

em.start(1)
em.stop(1)

This allows the measurement to be manually started and stopped. A pin to automatically start and stop measurements can be set up too. Note the start call is not needed for this, as the device will automatically start. The device can then be polled for a completed measurement:

em.setTrigger("PA0", 1)

while not em.measurementCompleted(1):
    sleep(0.1)

m = em.getMeasurement(1)

The above snippet sets a trigger on PA0. The returned measurement has several properties with metrics about the run:

m.energy        # Energy, joules
m.time          # Time between start and stop
m.avg_power     # Average power throughout the run
m.avg_current   # Average current throughout the run
m.avg_voltage   # Average voltage throughout the run

Platform run

These scripts form the basis to easily run binaries on a range of platforms. For example, to run a binary on the STM32F0DISCOVERY board, this is simply the following command line invocation:

$ platformrun stm32f0discovery program.elf
Energy:            27.386 mJ
Time:             626.119 ms
Average current:   14.382 mA
Average voltage:    3.041 V

The compilation of programs to run on the target architecture is out of scope for this document. The only particular feature a program must have, is that it asserts a digital 1 on a pin when it wants the measurement to start, and returns to 0V when the measurement should end.

Two configuration files are needed by platformrun, one describing the set of up the energy monitors, and one describing where platformrun can find all the tools necessary to run on a specific platform. The first file must be created manually - it is specific to the way you connect the boards, and the serial numbers given to the energy monitors.

A detection script is provided to find locations of the tools necessary to run binaries on a platform. The configuration of the location of tools, and enabled platforms is kept in ~/.platformrunrc.

The configuration file is set up as follows:

$ platformrun-detect

Summary

pic32mx250f128b           disabled
stm32vldiscovery          enabled
atmega328p                enabled
stm32f0discovery          enabled
msp-exp430fr5739          enabled
msp-exp430f5529           enabled

This will try to automatically detect where the required executables are.

List of platforms

Currently, several different platforms are set up to easily have programs run via platform run.

STM32F0DISCOVERY

This board contains a cortex-m0. Stlink is used as a gdb-server and an arm debugger is used to flash the code to the board.

Platform name: stm32f0discovery