MF4_CREATE_WRITER
Python Code
from flojoy import (
flojoy,
Stateful,
DeviceConnectionManager,
DataContainer,
HardwareDevice,
Directory,
File,
)
from typing import Optional, Literal
import can
import os
@flojoy(deps={"python-can": "4.3.1", "asammdf": "7.4.1"})
def MF4_CREATE_WRITER(
dir: Directory,
filename: str = "can_exported.mf4",
database: Optional[File] = None,
compression_level: Literal[
"No compression",
"Deflate (slower, but produces smaller files)",
"Transposition + Deflate (slowest, but produces the smallest files)",
] = "No compression",
default: Optional[DataContainer] = None,
) -> Stateful:
"""Create a writer for the MF4 format.
Logs CAN data to an ASAM Measurement Data File v4 (.mf4) as specified by the ASAM MDF standard (see https://www.asam.net/standards/detail/mdf/).
MF4Writer does not support append mode.
Parameters
----------
dir : Directory
The directory to export to.
filename : str
The name of the file to output.
database : Optional[File]
Path to a DBC or ARXML file that contains message description.
compression_level : Literal
The compression level to use. Defaults to "No compression".
Returns
-------
Stateful
A stateful object that can be used to write CAN data to the file.
"""
if dir is None:
raise ValueError("Please select a directory to export the data to")
filename = f"{filename}.mf4" if filename[-4:] != ".mf4" else filename
cpr_lvl = {
"No compression": 0,
"Deflate (slower, but produces smaller files)": 1,
"Transposition + Deflate (slowest, but produces the smallest files)": 2,
}[compression_level]
writer = can.io.MF4Writer(
os.path.join(dir.unwrap(), filename),
database=database.unwrap() if database is not None else None,
compression_level=cpr_lvl,
)
# Handle cleanup automatically
DeviceConnectionManager.register_connection(
HardwareDevice("MF4_writer"), writer, cleanup=lambda writer: writer.stop()
)
return Stateful(writer)
Example App
This application demonstrates how to use multiple CAN blocks to connect to a PEAK-USB device and read messages from it. The PEAK-USB device is a USB-to-CAN interface that enables you to connect a computer to a CAN network. This device is used in this case to capture the messages of a particular sensor by filtering them directly at the kernel level, thus reducing the load on the CPU, and save those messages to a log file locally.
Once the app is done, the generated logs are exported to an S3 bucket to keep a record of the sensor’s data for further analysis.
To replicate this application, you must connect the PEAK-USB to your computer and install the required driver (refer to the PEAK_CONNECT blocks for more information on the necessary driver for your platform). Then, simply specify the PEAK-USB channel in the required blocks, and this Flojoy application will log the messages received by the device!
Detecting channels
A valuable block is the PEAK_DETECT_AVAILABLE_DEVICE. This block allows you to display the devices using the PCAN interface that are connected to your computer.