Weird unicode character when using stdin stdout without buffer.

[techcatgato]

Hi all! I "solved" my previous problem of using stdin stdout "normally" without a buffer with this code:
on hub:

from pybricks.pupdevices import Motor
from pybricks.parameters import Port
from pybricks.tools import wait

# Standard MicroPython modules
from usys import stdin, stdout
from uselect import poll

motor = Motor(Port.A)

# Optional: Register stdin for polling. This allows
# you to wait for incoming data without blocking.
keyboard = poll()
keyboard.register(stdin)

while True:

    # Let the remote program know we are ready for a command.
    stdout.write("rdy")

    # Optional: Check available input.
    while not keyboard.poll(0):
        # Optional: Do something here.
        wait(10)

    # Read three bytes.
    cmd = stdin.read()

    # Decide what to do based on the command.
    if cmd == "fwd":
        motor.dc(50)
    elif cmd == "rev":
        motor.dc(-50)
    elif cmd == "bye":
        break
    else:
        motor.stop()

on pc:

# SPDX-License-Identifier: MIT
# Copyright (c) 2020 Henrik Blidh
# Copyright (c) 2022-2023 The Pybricks Authors

"""
Example program for computer-to-hub communication.

Requires Pybricks firmware >= 3.3.0.
"""

import asyncio
from contextlib import suppress
from bleak import BleakScanner, BleakClient
from ustruct import unpack

PYBRICKS_COMMAND_EVENT_CHAR_UUID = "c5f50002-8280-46da-89f4-6d8051e4aeef"

# Replace this with the name of your hub if you changed
# it when installing the Pybricks firmware.
HUB_NAME = "TC"


async def main():
    main_task = asyncio.current_task()

    def handle_disconnect(_):
        print("Hub was disconnected.")

        # If the hub disconnects before this program is done,
        # cancel this program so it doesn't get stuck waiting
        # forever.
        if not main_task.done():
            main_task.cancel()

    ready_event = asyncio.Event()

    def handle_rx(_, data: bytearray):
        if data[0] == 0x01:  # "write stdout" event (0x01)
            print("hi")
            payload = data.decode()

            if payload == "rdy":
                ready_event.set()
            else:
                print("Received:", payload)

    # Do a Bluetooth scan to find the hub.
    device = await BleakScanner.find_device_by_name(HUB_NAME)

    if device is None:
        print(f"could not find hub with name: {HUB_NAME}")
        return

    # Connect to the hub.
    async with BleakClient(device, handle_disconnect) as client:

        # Subscribe to notifications from the hub.
        await client.start_notify(PYBRICKS_COMMAND_EVENT_CHAR_UUID, handle_rx)

        # Shorthand for sending some data to the hub.
        async def send(data):
            # Wait for hub to say that it is ready to receive data.
            await ready_event.wait()
            # Prepare for the next ready event.
            ready_event.clear()
            # Send the data to the hub.
            await client.write_gatt_char(
                PYBRICKS_COMMAND_EVENT_CHAR_UUID,
                b"\x06" + data,  # prepend "write stdin" command (0x06)
                response=True
            )

        # Tell user to start program on the hub.
        print("Start the program on the hub now with the button.")

        # Send a few messages to the hub.
        for i in range(5):
            await send("fwd")
            await asyncio.sleep(1)
            await send("rev")
            await asyncio.sleep(1)
            print(".", end="", flush=True)

        # Send a message to indicate stop.
        await send("bye")

        print("done.")

    # Hub disconnects here when async with block exits.


# Run the main async program.
if __name__ == "__main__":
    with suppress(asyncio.CancelledError):
        asyncio.run(main())

However. when i turn on this program i get:

Any attempt so far to get rid of the weird unicode character in the beginining didnt work, and make the hub disconnect. ive tried replace(), strip(), and getting [:1] and all of these make the hub disconnect. Modifying the pc code to handle this character in the if loop also disconnects. Do you know any way of getting rid of this character?

[BertLindeman]

Have played your scenario here on a prime hub with a non stable firmware on windows 11.

Seen:

python issue_1822_pc_program.py
Start the program on the hub now with the button.
hi
Received: ('primehub', '3.5.0
hi
Received: ', 'ci-build-3540-v
hi
Received: 3.
hi
Received: 5.0-90-g9d3a6f85 on
hi
Received:  2024-09-06')

hi
Received: rdy
hi
Received: The program was sto
hi
Received: pped (SystemExit).

No garbage before rdy.

What firmware do you use. (I did not remember...)

Bert

[techcatgato]

Hi, where can I find the ZIP for the latest non stable version?

[BertLindeman]

In pybricks-micropython actions

The top entry is the latest.

[techcatgato]

Couldn't you just use a compatible browser on windows / linux / android just to install the firmware?

when i try to the hub isnt on the connection menu, and i have the driver

[BertLindeman]

From what environment / what browser is that?

[techcatgato]

From what environment / what browser is that?

Chrome on a guest tab

[BertLindeman]

There might be some experimental chrome://flags needed to enable, but I am not sufficiently known with that.

Sorry.

Maybe Pybricks getting started can help?

Bert

[techcatgato]

There might be some experimental chrome://flags needed to enable, but I am not sufficiently known with that.

Sorry.

Maybe Pybricks getting started can help?

Bert

Hi, after a lot of time I just can't install nightly. That should be fine imo cause my pybricks firmware is very new and the chances that i just missed the update that fixes that are low imo. Do you think theres anything else that can cause the weird �? every method of decoding in python i found leads to "�rdy"

[techcatgato]

I have identified the character to be u\0001, But I still can't get rid of it or process it, even with the beta firmware i managed to install

[BertLindeman]

On windows?

I know nothing about pycharm.
These tests run in a command prompt, here.
Could you run the PC side in a simple command prompt?

[techcatgato]

I'll try. Do you mean the regular python cmd like console?

[BertLindeman]

yes

[techcatgato]

I solved this but I have another problem, now when the payload == "rdy" is true, the hub disconnects when it tries to execute ready_event_set()

[dlech]

If you can share a Python script and Pybricks firmware version that reproduces the problem, we can look into it.