Control Myxa with UART

mah · February 3, 2021, 2:45am

Hi,
I’m trying to control the Myxa with an Arduino over serial. Is there a document somewhere that explains how to format the serial packets and what parameters can be read/written? I couldn’t find what I needed in the knowledge base.

pavel-kirienko · February 3, 2021, 10:48am

Currently, the best we can offer is this:

but we are working on supporting UAVCAN v1 in Myxa, which will be available not only as UAVCAN/CAN but also as UAVCAN/serial via UART and USB.

mah · February 5, 2021, 9:10am

Hi Pavel,
I was able to control the motor and get telemetry over UART by copying the parsers in messages.py in Kucher. However, I can’t find the part where we find part at the very beginning when you get the hardware/firmware version after connecting. Can you point me to the right location to find the correct packet structure?

pavel-kirienko · February 5, 2021, 3:33pm

It’s here:

github.com

Zubax/popcop/blob/master/python/popcop/standard/endpoint_info.py

#
# The MIT License (MIT)
#
# Copyright (c) 2017-2018 Zubax Robotics
#
# Permission is hereby granted, free of charge, to any person obtaining a copy of
# this software and associated documentation files (the "Software"), to deal in
# the Software without restriction, including without limitation the rights to
# use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
# the Software, and to permit persons to whom the Software is furnished to do so,
# subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in all
# copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
# FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
# COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
# IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN

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mah · February 5, 2021, 7:17pm

Is there a table somewhere to look up the “frame type code”?

pavel-kirienko · February 5, 2021, 7:26pm

For standard messages there is only one frame type code:

github.com

Zubax/popcop/blob/f45deea2486fa1d5f18d575c7eba7197bbd22e32/python/popcop/init.py#L33


# Author: Pavel Kirienko <pavel.kirienko@zubax.com>
#


import sys




if sys.version_info[:2] < (3, 5):
    raise ImportError('A newer version of Python is required')




STANDARD_FRAME_TYPE_CODE = 0xFF
MAX_APPLICATION_SPECIFIC_FRAME_TYPE_CODE = 0x7F




from . import transport, standard, physical




__version__ = 0, 1, 0


__author__ = "Pavel Kirienko"
__license__ = "MIT"

For application-specific:

github.com

Zubax/kucher/blob/fced36646d693fbdd6baa30cbcafaae11ef45cdd/kucher/model/device_model/communicator/messages.py#L459-L464


self._type_mapping: typing.Dict[MessageType, typing.Tuple[int, con.Struct]] = {
    MessageType.GENERAL_STATUS:         (0, GeneralStatusMessageFormatV1),
    MessageType.DEVICE_CHARACTERISTICS: (1, DeviceCharacteristicsMessageFormatV1),
    MessageType.COMMAND:                (2, CommandMessageFormatV1),
    MessageType.TASK_STATISTICS:        (3, TaskStatisticsMessageFormatV1),
}

mah · February 6, 2021, 6:16pm

Thanks, I got it working.

If anyone else needs to control Myxa with an Arduino over UART, I uploaded my code here:

My MCU was the Teensy4.0.