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pyenergy 0.1rc2

An interface to the MAGEEC energy monitor boards

Latest Version: 0.1rc7

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 changeserial SERIAL NEWSERIAL

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")

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

Prerequisites for running:
  • st-util (st-link package)
  • arm-none-eabi-gdb (or other arm gdb-compatible debugger)

ATMEGA328P

This is an ATMEGA328P chip, loaded with an arduino compatible bootloader. This is programmed with a USB to serial converter and avrdude. This was tested on a breadboarded ATMEGA328P chip, with a FTDI USB to serial converter.

Platform name: atmega328p

Prerequisites for running:
  • avrdude
  • avr-objcopy

PIC32MX250F128B

This is a 32-bit pic chip, tested on a breadboard and hooked up to a pickit2. This requires pic32prog (so that no bootloader is needed on the PIC chip) and the pic32 tools to convert the elf to a hex file.

Platform name: pic32mx250f128b

Prerequisites for running:
  • pic32prog
  • pic32-objcopy

Measurement configuration

The measurement configuration file tells platformrun about the energy monitors connectted to the platforms, and some additional details about the platforms. For example, to measure the stm32f0discovery, the application needs to know the serial number of the energy measurement device, as well as the measurement point and the shunt resistor value. Other platforms have additional details, such as atmega328p, which needs to know the ID of the USB-serial adaptor.

The measurement config is a standard JSON format file, and by default is loaded from ~/.measurementrc. An example of the measurement configuration for the stm32f0discovery platform is given below.

{
    "stm32f0discovery" : {
        "energy-monitor" : "CXM0",
        "trigger-pin" : "PA0",
        "measurement-point" : 1,
        "resistor" : 1
    }
}

Basic configuration

Keys:
  • energy-monitor. This specifies the serial number of the energy monitor that is used for this platform.
  • trigger-pin. This specifies the pin on which the platform will trigger the energy monitor.
  • measurement-point. Which measurement point is connected to the platform.
  • resistor. The value of the shunt resistor that intercept's the platform's power supply.

Platform specific keys

Keys for atmega328p:
  • serial-dev. This specifies the ID of the USB to serial device. This ID comes directly from the link found in /dev/serial/by-id/ when the adapter is plugged in. By selecting the ID this way, multiple similar USB-serial adapters can be uniquely specified.
Keys for pic32mx250f128b:
  • serial-number. This specifies the serial number of the pickit2 connected to the platform (not currently used).
 
File Type Py Version Uploaded on Size
pyenergy-0.1rc2-py2.7.egg (md5) Python Egg 2.7 2014-02-19 36KB
pyenergy-0.1rc2.tar.gz (md5) Source 2014-02-21 17KB
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  • Author: James Pallister
  • Keywords: energy monitor MAGEEC
  • License: GPLv3
  • Package Index Owner: James.Pallister
  • DOAP record: pyenergy-0.1rc2.xml