Interface configuration

Before setting up PyVISA you need to setup your interface.

USB

Notes

• For Serial over USB, read the Serial / RS232 section.
• See here for a USB oscilloscope example script.

Windows

After following the NI-VISA + PyVISA install guide it works out of the box.

Linux

You will need to add a Udev rule that grant your user raw access to USB devices. For added security, you can instead grant access to a specific device only (see note below).

1. Create Group: Create a new group called usbgroup.

   sudo groupadd usbgroup

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2. Add User to Group: Add the current user to the usbgroup group.

   sudo usermod -aG usbgroup $USER

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3. Create Udev Rule: Authorize raw USB access to a group called usbgroup.

   sudo bash -c 'cat > /etc/udev/rules.d/99-usbgroup.rules <<EOF
   SUBSYSTEM=="usb", GROUP="usbgroup", MODE="0666"
   EOF'

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4. Reload Udev Rules: to apply the changes.

   sudo udevadm control --reload-rules
   sudo udevadm trigger

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5. Reboot your system: sudo reboot

Now go to the Linux PyVISA setup.

Note: adding a Udev Rule for a Specific USB Device

1. Identify USB Device

Use lsusb to find the vendor ID (VID) and product ID (PID) of your USB device.

Bus 003 Device 011: ID VID:PID Your SCPI / VISA compatible measuring instrument

1. Create Udev Rule: Create a udev rule for your specific USB device.

   sudo bash -c 'cat > /etc/udev/rules.d/99-mydevice.rules <<EOF
   SUBSYSTEM=="usb", ATTR{idVendor}=="VID", ATTR{idProduct}=="PID", GROUP="usbgroup", MODE="0666"
   EOF'

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2. Reload Udev Rules: to apply changes.

   sudo udevadm control --reload-rules
   sudo udevadm trigger

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3. Reboot if needed.

Ethernet

No special drivers are needed, it works out of the box in all OS. Skip to the Windows PyVISA setup or the Linux PyVISA setup.

Notes

• Your PC's firewall need to allow traffic on the instrument's port. Standard ports for protocols VXI-11: TCP 111, HiSLIP: TCP 4880.
• For raw sockets, specify the instrument's IP and port in its address: TCPIP::<IP>::<PORT>.

GPIB (IEEE488)

This interface requires a GPIB controller or a GPIB to USB adapter. These adapters are quite expensive, often over $150 for the cheapest ones. A cheaper Open-Source alternative exists for hobbyists: UsbGpib.

Windows

Install your adapter's drivers and go to the NI-VISA + PyVISA install guide.

Linux

If you are using an NI or Agilent card, the linux-gpib drivers should be installed. It is not a trivial setup and you should refer to Tom Verbeure's guide.

The UsbGpib's GitHub repo documents it's setup.

Serial / RS232

Notes

• An example script for a serial power supply is available here.
• You may need to set the baud rate of the connection using the baud_rate parameter in the open_resource method. Ex: open_resource("ASRL1::INSTR", baud_rate=115200).

Windows

Works out of the box. Serial VISA adress format expected: ASRL<X>::INSTR

Linux

For Linux (and UNIX) users, add your user to the dialout group:

sudo usermod -aG dialout $USER

Serial VISA adress format expected: ASRL/dev/ttyUSB<X>::INSTR or ASRL<X>::INSTR.

PXI

For PXI chassis, refer to the NI PXI Platform Services website. Drivers are available for Windows and Linux.

Termination Characters

Some devices expect termination characters at the end of the commands and send them at the end of answers. Refer to the device's manual but the most common characters are \n , r, and \r\n. For serial, the default is no write termination and \r for read termination.

Example:

inst.read_termination = "\n"  # Line Feed (LF)
inst.write_termination = "\r"  # Carriage Return + Line Feed