pxsi: parameter update over serial interface
============================================

Markus Zolliker (markus.zolliker@psi.ch)

helper library for micropython on RP2040 (e.g. Arduino Nano Connect or Paspberry Pico)

Code example
------------

    from pxsi import Pxsi
    
    # declare variables visibile over serial
    
    vars = Pxsi('MyBox',   # idn will be: pxsi,MyBox
        t = 5,
        a = 2,
    )

    # create action functions for some of the variables

    def change_t(value):
        # write here what to do when t changes

    # your real code
    
    print(t)  # the given variables are now available in the main namesapce

    while True:
        # handle IO, wait at most 0.5 secs
        vars.handle_io(0.5)
        # read out sensors, do control logic here
        # important: do not sleep here!


Serial protocol
---------------

Commands:

    name         # get value of variable name
    name=value   # change value (value must be a valid JSON value)
    ["name1", ["name2", value]]     # multiple commands: query name1, change name2. must be a valid JSON array
    {"name1": null, "name2": value} # alternative form - be aware that order is not guaranteed

Special command for identification

    *IDN?

returns:

    pxsi,<idn>


For all other commands the reply is always a JSON object:

    {"name1": value1, "name2", value2}

In case of an error, the result contains an item with the key "_error_" and a JSON array as value,
listing the errors appeared.


Hints for Arduino Nano Connect
------------------------------

For a soft reset send '\x03\x04' (Ctrl-C Ctrl-D).
The reply will be quite some text, with the last line:

    pxsi:<idn>