Finally I managed to switch the mode from Raspberry PI using ReaderThread. Here is the code:

import sys
import traceback
import argparse
import json
import serial
from serial.threaded import LineReader, ReaderThread
from time import sleep

MODES = [
    'Audio FFT',
    'Code Detector',
    'Face Detector',
    'Lane Line Tracker',
    'Motion Tracker',
    'Shape Matching',
    'Camera Stream',
    'Online Classifier',
    'Color Tracker',
    'Face Recognition',
    'Target Tracker',
    'Shape Detector',
    'Object Recognition',
]

ap = argparse.ArgumentParser()
ap.add_argument('-m', '--mode', help = 'Switch to mode: {}'.format(MODES))
ap.add_argument('-a', '--args', default = '', help = 'Some modes require extra args. For "Object Recognition" either "yolo_20class" or "nanodet_80class"')
args = vars(ap.parse_args())

if 'mode' not in args or args['mode'] not in MODES:
    ap.print_help()
    exit(1)

OBJECT_RECOGNITION_ARGS = [
    'yolo_20class',
    'nanodet_80class'
]
if args['mode'] == 'Object Recognition' and args['args'] not in OBJECT_RECOGNITION_ARGS:
    ap.print_help()
    exit(1)

class PrintLines(LineReader):
    def connection_made(self, transport):
        super(PrintLines, self).connection_made(transport)
        sys.stdout.write('port opened\n')

    def handle_line(self, data):
        sys.stdout.write('line received: {}\n'.format(repr(data)))

    def connection_lost(self, exc):
        if exc:
            traceback.print_exc(exc)
        sys.stdout.write('port closed\n')

with serial.Serial() as s:
    s.port = '/dev/ttyAMA0'
    s.baudrate = 115200
    s.timeout = .5
    s.open()

    with ReaderThread(s, PrintLines) as protocol:
        js = {
            'function': args['mode'],
            'args': args['args']
        }
        protocol.write_line(json.dumps(js))
        sleep(2)

And the output:

pi@rpi0:~/serial$ ./serial_mode.py --mode 'Object Recognition' --args 'yolo_20class'
port opened
line received: '{"msg":"function switched to object_recognition."}'
line received: '{"msg":"Running Object Recognition, Copyright 2021 M5Stack Technology Co., Ltd. All rights reserved.","running":"Object Recognition"}'
port closed

Hi there,

I'm trying to manage UnitV2 device by Serial port. Reading data works just fine, for example in the "Object detection" mode Unit sends data:

{'num': 1, 'obj': [{'prob': 0.697403133, 'x': 44, 'y': 8, 'w': 555, 'h': 466, 'type': 'person'}], 'running': 'Object Recognition'}
{'num': 1, 'obj': [{'prob': 0.684900761, 'x': 49, 'y': 1, 'w': 543, 'h': 468, 'type': 'person'}], 'running': 'Object Recognition'}
{'num': 1, 'obj': [{'prob': 0.686426222, 'x': 23, 'y': 2, 'w': 577, 'h': 472, 'type': 'person'}], 'running': 'Object Recognition'}

Unfortunately I can't manage to send commands and actually switch the mode. Here is my code for Raspberry PI(connected with UnitV2 by serial ports):

import serial, json

with serial.Serial() as s:
    s.port = '/dev/ttyAMA0'
    s.baudrate = 115200
    s.timeout = .5
    s.open()

    js = {
        'function': 'Camera Stream',
        'args': ''
    }
    print("send", js)
    s.write(json.dumps(js).encode('utf-8'))

    response = s.readline()
    print("receive", response)

And the output:

send {'function': 'Camera Stream', 'args': ''}
receive b''

Am I missing something?

Hello @felmue ,

In fact I received answer from M5 support in the morning. I managed to solder the cable to the right place and now fan works. Thank you for your help!

Here is the place:

Hi there. Does anybody know where plus(red) wire from fan is connected to the plate? My unit was overheating in 3 minutes after start and after disassemble it I noticed that this wire isn't connected.