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An extensible application framework with REPL for creating processes with side effects.

Project description

particle board REPL (PBR) program.

pip install Particle_Board_REPL

To run interactively in with the REPL.

PBR -r

This Module adds Particle board cli functionality along with various other higher level functions for interacting with boards. The idea is to make it possible to create a repeatable process which can interact test, and program a board.

This uses the cli, particle-cli in the Arch-linux AUR, to interface with a board, verify it's life, update it, claim/register it, flash it, test it, etc.

All of the commands here could be almost doable in a chain of 'do this', 'do that'. But the boards take time in between events. The USB device comes up and down constantly, it's not reliable just because you know that's where the board was. I have read about other gnu/linuxs which change the device on occasion or always. Arch does not. Once I have it, I have it. However, it comes and goes...

If a command fails at any point in a process, the entire process stops and the board is considered a failure.

So we have to wait, watch and listen.

But, as a whole, it's just a module of things we'd like to do. So we wrap those up to make life easier. and life is easier. At some point, making life is easier is just listing all the previous things that made life easier. And so it goes.

Particle Board REPL runs 4 ways.

Once you have some processes defined you can then run what you like in 4 different ways,w

  • run the autoexec setting once: PBR
  • Start a REPL -r
  • Run the autoexec setting in a loop with a continue dialog -i
  • To run commands instead of the autoexec, Just add them to the command.

PBR -r get list PBR -i get list PBR get list PBR -r msgbox "hello"

Getting Help

Help with the command line can be obtained with -h, Additionally, Help with the symbols which are available for programming in the yaml files or in the REPL are obtained with the help command, so help runs help.

  • PBR -h for cli help.
  • PBR help for internal help.
  • PBR particle-help for internal particle specific help.

The easiest way to understand this system by using the REPL. It will show you how it works. PBR -r

Once in the REPL at the prompt; PBR:>, There are two help commands. help and particle-help. Help shows all the commands known with their documentation. particle-help, show-all will show you everything there is to know about the state of things in yaml format. showin lets you drill in if you like.


It's the first command you'll want to do when you plug in your particle board.

This is the command we use to populate our usb device, board type and device-id. Various particle commands need the id, and we need the usb device so we know who to wait for. It uses particle serial list for it's data.

The first thing to do is a list and a get or just a get. From there the device id board type and usb device should be known. They will be used for other commands in the process.

If you know particle commands then those should make sense, this is a small subset of the possibilities.

The REPL will do whatever you ask, so help, show, list, identify, update, set-setup-done, etc. Some which require a bit more, such as entering dfu or listen mode, are wrapped up together for convenience, but also available as commands themselves. Lights.

Something very important for knowing the state of your boron.

The meaning of the lights on a Boron.

The modules,,, and Config.

The more complex Particle functions are in, These are functions which interact with the Application state as well as the device. This is also where the symbol tables are defined for the add on particle cli functionality.

There is very little in the module. Particle cli commands are one line functions, and truly many of them are unecessary as they could be done with the pcmd.

These are most of the basic particle-cli commands I've used so far. All of these functions are here to be as close to bare particle-cli commands as can be. I combined some things, like flash always does dfu first, identify always does a listen. Get is perhaps the most complex as it does wait and poll to give a chance for a reset or a plug. Internally there are a few versions of get to choose from.

The rest of the functions can actually live in the configuration file. It is only necessary to modify python code if there is a desire for more base functionality.

Current state

flash-test, flash-image, flash-tinker, are working, but through os.popen().read() instead of subprocess like everything else. I don't have an explanation, subrocess needs more configuration for these commands. I've tried shell=True with no change. So it's going be down in the details somewhere.

I had thought that perhaps using the particle.get_w_wait function to wait for the device could work nicely, but it does not.

login and log_out needed to be called with os.system in order for them to behave nicely with their prompts. Subprocess could work I think, but it's configuration is complex and it's not worth investigating.

The Internals.

This is at it's heart a simple Read Eval Print Loop. It has 4 ways of running, and it automatically manages Application state, yaml configuration files, the command line, dialogs, prompts, logging and help.
Everything needed for a particular application can be done with a module of functions..

The cli is done with argparse is extendible from the application layer as needed.

Python dialog, with several standard messages and boxes are included, as is a yaml configuration, and an Application state which contains everything known to the app.

Everything is extensible. Usually a few python functions and a configuration file is all you will need to create a nicely versatile application.

While there is a Repl available, and commands can be added, combined and remixed, they can also be run automatically through the autoexec setting in the config. The default autoexec is to provide help.


The Simple Process REPL uses YAML for it's configuration files.

Everything is specified there, there is very little in common with the cli. If no config file is given, the default SPR-config.yaml will be loaded if found. The primary purpose of the cli is to designate the fashion you would like for the REPL to run.

All necessary defaults are set within the package with SPR-defaults.yaml. When building an application, that application's defaults will be merged into the Simple_Process_REPL's default configuration before loading a locally defined SPR-config.yaml. An application can over-ride the configuration file name with a setting in the defaults section of the Application State.

4 modes of running

  • Run in a loop for doing a process over and over
  • Run the default process once
  • Run a list of command/symbols from the command line
  • As an interactive REPL

In any case, if any step fails, the process will fail. if in interactive loop mode, -i, the continue dialog will catch the fail for the next loop.

The default process

In the exec section of the configuration there is an autoexec attribute. This should be a symbol name or list of symbol names to run as the default process. This is the process that will run when running cli in interactive loop mode, or when run once.

If commands are given on the cli after the option then that list is executed once automatically instead of the commands in autoexec.

The easiest way to understand this is system is by using the REPL. It will show you how it works. PBR -r

Then type help, particle-help, and showin. Read It!

Once in the REPL at the prompt; __PBR:>, help shows all the commands known with their documentation.


There are three kinds.

  • Symbols which point at directly at parameter-less functions
  • Symbols which are lists of symbols, compound commands.
  • Symbols which are special because they take parameters.


These commands are just python functions, whatever it is they do. Usually, manipulate the application state, and/or interact with something.

Compound commands

Compound commands are commands defined outside of python code. They are strings which can be parsed and evaluated by the REPL/interpreter.

Compound commands can be built from other compound commands and special commands. Compound commands can be defined in the configuration yaml, in python code, or interactively in the REPL.


The REPL is very convenient as it saves state, and can be used to interactively create/execute a process step by step. help at the REPL prompt.

  • Builtins help
  • showin, are quite handy.
  • REPL prompt: persistent history and tab completion.
  • The loglvl command can change the logging level interactively.
  • Defining a symbol of a special works. - Super cool.
    • msgbox "Hello World"
    • def mymsg "my special msg" msgbox "Hello World"
  • log-info and log-debug allow sending of arbitrary messages to the log.
  • sh for running shell commands.
  • pcmd for running particle-cli commands.

Application State.

AS = {
    "config": {},
    "args": {},
    "defaults": {
        "config_file": "PBR-config.yaml",
        "loglevel": "info",
        "logfile": "PBR.log",
    "device": {"id": "", "name": "", "path": ""},
    "wifi-connected": False,
    "platform": platform(),
  • configuration is the merged yaml configurations
  • args is the resolved command line
  • defaults is used by argparse to supply default options to the command line.
  • device is an imaginary device. Which we can wait for and handshake with.

The command: showin in the REPL will give it to you in yaml. help will give you the documentation for every command you can do, even the ones you just created. The easiest way to access it is showin device or showin config serial with showin key1 key2,... is the command to find sub-section or attributes in the REPL. showin config , showin defaults, or just showin which is the same as show-all.

For an Application layer, it is only necessary to provide a structure as desired, which will be merged directly onto this structure.

It's a Simple list processor.

This program is actually a very simple interpreter with an interactive REPL. Everything you want to do must be a python function which is registered in the interpreter's symbol table. From there, everything is composable from symbol/words from the interpreter's symbol table, ie, your symbols. Those composed symbols can also be added to the interpreter's symbol table to create increasingly complex sets of processes, which are executed in order. These user functions can also be defined in the YAML config file.

It has a really, really stupid parser. All it can do execute a list of symbols, or call a special symbol with everything that follows. It does know the difference between symbols, strings and numbers.

Basic symbol/functions should be functions done entirely for their side-effects. They take no parameters and give no return. Special Symbols can take arguments.

At the lowest level the symbols/commands are directly connected to python functions. But symbols/commands can also be lists of known symbols instead of a function. This allows for the creation of sub-groups which can be referenced by other symbols. There are no parentheses, only the ability to associate lists of symbols with a new symbol.

import repl as r
symbols = [
    ['wifi',       connect_wifi,    'Connect to wifi using nmtui if not connected.']
    ['list',       P.list_usb,      'List the boards connected to USB.']
    ['start',      'wifi list',     'Connect wifi and list the boards.']
    ['identify',   P.identify,      'Try to identify a device.']
    ['domore',     'start identify', 'Start then identify']
    ['doevenmore', 'domore setup',   'Start identify and setup.']

The symbols start, domore and doevenmore can be defined in the YAML configuration file, it is not necessary to modify python code unless new functionality needs to be introduced.

Special Symbols

The interpreter is not very bright and has no way of grouping things together which makes it difficult to execute commands which take arguments. Specials are symbols at the beginning of a command which will eat the rest of the line, in attempt to do what they are supposed to do.

To compensate the interpreter has the concept of special symbols, These are symbols which take arguments and can consume the entire REPL command.

These are also pointers to python functions, but which take some arguments. These go on a line by themselves since we have no way of knowing them unless the line starts with them, and then the special gobbles up the rest of the line.

The REPL itself has a special symbol, def which allows for the creation of a new symbol with the following syntax.

def <symbol> 'helpstr' symbol1 symbol2 symbol3...

Other commands are save-config, load-config, msgbox, msgcli, loglvl, log-info, showin, etc.

Special symbols have an argument count which can be set. If positive the command will be checked for compliance. Here is an example which creates symbols for saving and loading configurations from a given filename.

specials = [
    "Commands we want in the repl which can take arguments."
    ['save-config', save-config, 1,
    "Save the configuration; save-config 'filename'"]

    ['load-config', load-config, 1,
    "Load a configuration; save-config 'filename'"]

Core: generic functionality

There are a few builtins which do special things. There is wait which just waits for a device to come online with a timeout. There is pause which just sleeps for a few seconds as set in the configuration. The wifi function checks the wifi with linux's network manager, and uses nmcli to create a connection if one does not exist. Functionality is easy to add with a new function and an entry in the symbol table.

  • dialogs - There are some python dialog, and cli interface functionalities.
  • wifi, - Uses network manager (nmcli) for linux. Non-functional on other platforms.
  • Waiting and handshaking.
    • wait looks for the actual device path i/o event with a timeout.
    • pause sleeps for pause_time. Note: wait for device is literally a poll to see if the device file exists. Once it appears there is some time before the udev rules make the file accessible by non-root users. A pause helps everything go smoothly. The next command will actually have access to the device. So now I have a habit of following a wait with a pause.
    • handshake does a blocking for both the initial string, and the test results after.

Handshake function

This is a generic function that is a bit more complicated.
It manages an interaction with a device. Everything handshake does is defined in the configuration file. As with everything else, if anything fails, or doesn't match, an exception is raised.

Here are the steps that handshake() does.

  • Wait for the start_string, match it.
  • Respond with the response_string.
  • Look in the output for:
    • fail_regex,
    • done_regex,
    • do_qqc_regex.
  • If fail, raise an exception.
  • if done, exit quietly with true.
  • if do_qqc, then call the do_qqc_function and send the return value to the serial device.

qqc = quelque chose = something.

In the config the do_qqc_function is set to input-serial, as an example. Input-serial prompts for a serial number, validates it, and returns it. This function must be listed in the symbol table as that is where handshake() will look for it. Makes it easy to test. serial-input at the SPR:> prompt.

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