dstdsv 0.1.1

Python driver for IMADA DST/DSV Force gauges

Python module to access to Imada DST/DSV series devices

• Florian Dupeyron <florian.dupeyron<at>mugcat.fr>
• July 2024

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This is a simple python library that allows to pilot an imada DST/DSV series force gauge.

The following basic features are implemented:

• Get a measure
• Reset the measurement
• Set measure mode (Realtime / Peak)
• Set the measure unit (Newton / Kilograms)
• Set limit points (above and below limits)
• Store last measure in memory
• Clear last stored measure in memory
• Clear all stored measures
• Turn off the device

Installation

pip install dstdsv

This package depends on pyserial to handle serial communication.

Test your setup

To test your setup, two utility scripts are available:

• dstdsv.utils.list_devices: List compatible devices found on PC (when connected using USB cable);
• dstdsv.utils.test_measure: Test 10 measures on first found compatible devices

For instance, on my linux machine:

> python -m dstdsv.utils.list_devices
Found compatible devices:
- /dev/ttyUSB3: DSV/DST Series - DSV/DST Series

> hatch run python -m dstdsv.utils.test_measure
Measured data [Decimal('0.00'), Decimal('0.00'), Decimal('0.00'), Decimal('0.00'), Decimal('0.00'), Decimal('0.00'), Decimal('0.00'), Decimal('0.00'), Decimal('0.00'), Decimal('0.00')]

Basic usage

Two top level calsses are available to access the device, according to used link type :

• GaugeUSBDevice when the device is linked using USB ;
• GaugeSerialDevice when the device is linked using RS232C Connector.

Here is a basic example that does 10 measurements, each 100ms :

from dstdsv import (
    GaugeUSBDevice,
    GaugeMeasureMode,
    GaugeMeasureUnit
)

import time

SERIAL_DEVICE = "COM23" # Path to serial device


if __name__ == "__main__":
    with GaugeUSBDevice(SERIAL_DEVICE) as gauge:
        # Initial setup
        gauge.unit_set(GaugeMeasureUnit.Newton)
        gauge.mode_set(GaugeMeasureMode.Realtime)

        # Do 10 measures
        measures = []
        for i in range(10):
            curtime = time.time()
            nexttime = curtime + 0.1 # Time to next measure

            measure = gauge.measure()
            measures.append(measure.value)

            time.sleep(nexttime-time.time()) # Sleep until next measure time

Optionally, the dstdsv.find_devices() function can be used to find compatible devices:

from dstdsv import (
    GaugeUSBDevice,
    GaugeMeasureMode,
    GaugeMeasureUnit,
)

import time

if __name__ == "__main__":
    # Find compatible devices
    devices = find_devices()

    if not devices: # If list is empty, raise an error
        raise RuntimeError("Found no compatible device")

    selected_dev, selected_dev_description = devices[0] # Select the first found device

    print(f"- Use found device at {selected_dev}: {selected_dev_description}")

    with GaugeUSBDevice(selected_dev) as gauge:
        # Initial setup
        gauge.unit_set(GaugeMeasureUnit.Newton)
        gauge.mode_set(GaugeMeasureMode.Realtime)

        # Do 10 Measures
        measures = []
        for i in range(10):
            curtime = time.time()
            nexttime = curtime + 0.1

            measure = gauge.measure()
            measures.append(measure.value)

            time.sleep(nexttime-time.time()) # Sleep until next measure time

Note for linux users

By default, the device shall not be recognized by a linux system. But as the devices uses a FTDI-X chip to implement the USB/serial ink, the ftdi_sio driver can be used to access the device, which should be available on most linux systems.

First, identify the VID/PID of the device using the lsusb command:

For DST/DSV devices, tthe VID should be 1412, and the PID should be 0200.

Next, you need to load the ftdi_sio module (as root):

# modprobe ftdi_sio

Next, you can register the VID/PID using the following command (as root):

# echo <VID> <PID> > /sys/bus/usb-serial/drivers/ftdi_sio/new_id

For example, in our case:

# echo 1412 0200 > /sys/bus/usb-serial/drivers/ftdi_sio/new_id

After that, we can verify in the kernel logs (using the dmesg command), that our device has been recognized:

[ 5351.072861] usb 2-1.8.2: new full-speed USB device number 4 using ehci-pci
[ 5351.179497] usb 2-1.8.2: New USB device found, idVendor=1412, idProduct=0200, bcdDevice=10.00
[ 5351.179519] usb 2-1.8.2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 5351.179532] usb 2-1.8.2: Product: DSV/DST Series
[ 5351.179534] usb 2-1.8.2: Manufacturer: IMADA CO.,LTD.
[ 5351.179536] usb 2-1.8.2: SerialNumber: DS31ODMQD
[ 5735.295799] usbcore: registered new interface driver ftdi_sio
[ 5735.295819] usbserial: USB Serial support registered for FTDI USB Serial Device
[ 5927.406465] ftdi_sio 2-1.8.2:1.0: FTDI USB Serial Device converter detected
[ 5927.406555] usb 2-1.8.2: Detected FT-X
[ 5927.407719] usb 2-1.8.2: FTDI USB Serial Device converter now attached to ttyUSB3

It's a win! The device has been recognized and attached to device /dev/ttyUSB3. It shall also be available in /dev/serial/by-id/ usb-IMADA_CO._LTD._DSV_DST_Series_<SERIAL_NUMBER>-if00-port0.

Now, please note that after reboot, this configuration will be lost. To make it permanent, the best is to create an udev rule that triggers those commands when the device is plugged in.

Create the /etc/udev/rules.d/80-imada_dstdsv.rule file with the following content:

ACTION=="add", ATTRS{idVendor}=="1412", ATTRS{idProduct}=="0200", RUN+="/sbin/modprobe ftdi_sio" RUN+="/bin/sh -c 'echo 1412 0200 > /sys/bus/usb-serial/drivers/ftdi_sio/new_id'"

After that, reload the udev rules:

# udevadm control --reload

Optionally, you can trigger the rules:

# udevadm trigger

cf. https://stackoverflow.com/questions/442833/how-to-force-driver-to-device-match-in-linux for more info.

TODO

• Create an async variant using pyserial-asyncio

License

dstdsv is distributed under the terms of the MIT license.