from pxsi import Pxsi

# declare variables visibile over serial

with Pxsi('MyBox'):   # idn will be: pxsi,MyBox
    pollinterval = 5.0  # important: add decimal point in case you want this to be a float
    anint = 2
    afloat = 0.0      
    astring = 'text'

# the given variables are now available in the main namespace

# create action functions for some of the variables

def change_afloat(value):
    value = float(value)  # check value is compatible with float
    # write here what to do when t changes
    return value  # return the validated value

# the validity of <value> has to be checked here, and if any conversion happens
# the converted value has to be returned
# if no change function is present, the value is converted to the type of
# the initial value (e.g. float, int or str)

# here follows your real code

while True:
    # handle IO, wait at most 0.5 secs
    Pxsi.handle(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

The values must match the type of initial values

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>