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>