udmx-pyusb 2.0.0

uDMX Interface Library

Programming the Anyma uDMX interface (and clones) Using Python and PyUSB

Copyright © 2016 by Dave Hocker ([e-mail])

Overview

The purpose of this repo is to share what I have learned about programming the Anyma uDMX interface using Python and PyUSB on the Raspberry Pi (RPi). Th Anyma uDMX interface is relatively inexpensive and there are a large number of clones available from sites like eBay. However, there seems to be a dearth of information available for programming this interface under Linux (Raspbian Jessie in this case).

Many thanks go out to Markus Baertschi and the work he did on the uDMX-linux utility (see https://github.com/markusb/uDMX-linux). His C++ based uDMX utility served as the basis for the majority of my learning exercise.

License

The work presented here is licensed under the GNU General Public License v3 as published by the Free Software Foundation, Inc.. See the LICENSE file for the full text of the license.

Source Code

The full source is maintained on GitHub.

Development Environment

Virtual Environment

This work was originally written in Python 2.7 but has been adapted for both Python 2 and Python 3. Version 1.1.0 works on Python 2. Version 2.0.0 and above works on Python 3.5+. A suitable development environment would use virtualenv and virtualenvwrapper to create a working virtual environment. The requirements.txt file can be used with pip to create the required virtual environment with all dependencies.

Here are some references for setting up virtualenv and virtualenvwrapper.

• virtualenv and virtualenvwrapper
• virtualenv and virtualenvwrapper on Linux
• pip and virtualenv on Windows
• virtualenvwrapper on Windows
• virtualenv and virtualenvwrapper on macOS

A quick Internet search will reveal many articles on how to install and setup virtualenv/virtualenvwrapper on most any OS.

PyUSB

PyUSB requires one of the following: libusb 1.0, libusb 0.1 or OpenUSB. See 5. libusb 1.0 is part of the Raspbian Jessie image available from raspberrypi.org. How to install libusb on Windows and macOS is covered below.

Operating Systems

Raspbian

The main purpose of this project was to learn about using the uDMX interface on an RPi. And, this is the primary environment where the author deploys the code.

macOS

However, enough of the work was done on OS X 10.11.3 to conclude that this code will work or can be made to work on both OSes. If you want to try it on OS X, use brew to install libusb (it will install libusb 1.0).

Windows

The code has also been tested on Windows 10. To get this to work, you must install a Windows version of libusb. There are likely a number of ways to get a libusb installed. However, the following libusb version has been successfully tested: libusb-win32 using this
installer. The key is to follow the instructions for the "Driver Install Creator Wizard". You need to create a driver for the uDMX interface.

Programs and Modules

tryusb.py Program

This was my first learning tool. It does the following:

• Locates the uDMX interface.
• Prints some information about the interface.
• Sends some basic commands to a Venue ThinPar64 demonstrating how to manipulate the light via DMX.

It also helped me resolve some issues with permissions on the RPi. To run this app:

python tryusb.py

uDMX.py Program

This program functions pretty much like the C++ based uDMX utility from Markus Baertschi. To get help, try

./uDMX --help
or
python uDMX.py --help

For each invocation, this program does the following:

• Loads the uDMX.conf file from /etc/uDMX.conf.
• Activates the virtualenv defined in the conf file IF PyUSB is not found in the current environment.
• Loads the .uDMXrc file defined in the conf file.
• Locates the uDMX interface based on vendor ID and product ID.
• Sends the DMX message defined by the command line arguments.

uDMX.py uses the pyudmx.py module.

pyudmx.py Module

The pyudmx.py module provides a simple, easy to use module for talking to the uDMX interface. Essentially, it is a uDMX specific adapter on top of the pyusb module. If you want to write a uDMX oriented application consider starting with pyudmx.py.

Simple usage example:

dev = pyudmx.uDMXDevice()
dev.open()
dev.send_single_value(1, 255) # sends the value 255 to DMX channel 1
dev.close()

In this example, the open() method will default to opening the first uDMX interface with vendor ID 0x16c0 and product ID 0x05dc.

A more complete programming example can be found in the example.py file.

Learning Notes

Here are some notes from this learning exercise using Raspbian Jessie on an Rpi. The lessons learned here apply to most Linux systems, but probably do not apply to Windows or macOS.

Finding the uDMX Interface

As there is no kernel driver for the uDMX, it does not show up under /dev like /dev/tty.

You can locate it this way:

~/rpi/uDMX-pyusb $ lsusb

Bus 001 Device 005: ID 16c0:05dc Van Ooijen Technische Informatica shared ID for use with libusb
Bus 001 Device 004: ID 1a40:0201 Terminus Technology Inc. FE 2.1 7-port Hub
Bus 001 Device 003: ID 0424:ec00 Standard Microsystems Corp. SMSC9512/9514 Fast Ethernet Adapter
Bus 001 Device 002: ID 0424:9514 Standard Microsystems Corp. 
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

The uDMX is the first device at Bus 001, Device 005 with ID 16c0:05dc. The 16c0 is the vendor ID and the 05dc is the product ID. The uDMX can be found at /dev/bus/usb/001/005.

Permissions

If you want to program the uDMX on a raspberry pi without always running sudo, you must do something with the default permissions of the uDMX device.

~/rpi/uDMX-pyusb $ ls -al /dev/bus/usb/001/005
crw-rw-r-- 1 root root 189, 4 Feb 25 15:30 /dev/bus/usb/001/005

Notice the permissions are: 664. Only root and members of the root group have write permission. This is why sudo is required for the current user (usually pi). You can fix this issue by changing the permissions on the uDMX to: 666.

sudo chmod 666 /dev/bus/usb/001/005

Now check the permissions.

~/rpi/uDMX-pyusb $ ls -al /dev/bus/usb/001/005
crw-rw-rw- 1 root root 189, 4 Feb 25 15:30 /dev/bus/usb/001/005

Unfortunately, this is only a temporary fix. On the next reboot the permissions will revert back to their default 664. One way to permanently fix this problem is to write a udev rule that sets the permissions to 666 when the device is plugged in. Here's the rule.

SUBSYSTEM=="usb", ATTR{idVendor}=="16c0", ATTR{idProduct}=="05dc", MODE="0666"

You can take this solution by editing the 98-uDMX-usb.rules file and uncommenting the line that contains this rule. Copy the edited file to /etc/udev/rules.d.

sudo cp 98-uDMX-usb.rules /etc/udev/rules.d

To make sure the rule is used, pull the uDMX and replug it.

There is an obvious down side to this solution. It gives all users read/write access to the uDMX. We can limit read/write access to members of the pi group by changing the rule to:

SUBSYSTEM=="usb", ATTR{idVendor}=="16c0", ATTR{idProduct}=="05dc", GROUP="pi"

This rule leaves the permissions set to 664 while changing the ownership to root:pi. Overall, this is probably more desirable. The root user owns the device, members of the pi group (which includes pi) have read/write access and all other users have read-only access.

~/rpi/uDMX-pyusb $ ll /dev/bus/usb/001/005
crw-rw-r-- 1 root pi 189, 4 Feb 26 10:05 /dev/bus/usb/001/005

You can choose this rule by editing 98-uDMX-usb.rules file and uncommenting the line that contains this rule.

Symlinks

You can use a udev rule to create a symlink for a uDMX device.

SUBSYSTEM=="usb", ATTR{idVendor}=="16c0", ATTR{idProduct}=="05dc", GROUP="pi", SYMLINK+="uDMXusb%n"

This rule will produce a symlink for each uDMX device found.

~/rpi/uDMX-pyusb $ ll /dev/uDMXusb*
lrwxrwxrwx 1 root root 15 Mar 21 16:29 /dev/uDMXusb2 -> bus/usb/001/005

Looking at these permissions you might think that there is open access to the uDMX. However, that is not the case. The permissions of the the symlink target prevail. The symlink simply allows all access to the symlink itself.

~/rpi/uDMX-pyusb $ ll /dev/bus/usb/001/005
crw-rw-r-- 1 root pi 189, 15 Mar 21 16:29 /dev/bus/usb/001/005

Thanks to muzzol for this tip.

udev Rules

For more on udev rules see Writing udev rules.

Reboot Issues

This is an observation. On a warm reboot, the uDMX interface is not always found. You might have to replug the device to get Raspbian to find it. Why this happens is unclear.

Multiple uDMX Issues

It is possible to run multiple uDMX devices on one system, but it can be difficult. Most uDMX interfaces and clones do not have unique serial numbers. This makes identification of each interface problematic.

Given the detailed USB information shown below, the following is available to identify a uDMX.

• Vendor ID
• Product ID
• Manufacturer
• Product
• Serial
• Bus number
• Device number

Based on limited research it appears that only the Bus and Device numbers uniquely identify a given uDMX interace. The other values are likely to be the same for all uDMX interfaces based on the Anyma design and firmware. Unfortunately, the Bus and Device number cannot be used reliably because simply moving a uDMX to another USB port will change one or both of those values.

If you want to use multiple uDMX interfaces, you need to plug them in one at a time and use the lsusb command to determine the Bus and Device number for each one. And, after that you can't move them around.

The pyudmx.uDMXDevice.open() method will accept a bus number and device address if you need to manage multiple uDMX interfaces.

Unless otherwise indicated, the programs in this repo will work with the first uDMX interface they find.

Detailed USB Information

Here is a dump of innformation a uDMX clone. Most of the information in the dump seems to refer to the firmware manufacturer not the hardware manufacturer. The firmware is open source.

~/rpi/uDMX-pyusb $ lsusb -v

Bus 001 Device 005: ID 16c0:05dc Van Ooijen Technische Informatica shared ID for use with libusb
Device Descriptor:
  bLength                18
  bDescriptorType         1
  bcdUSB               1.01
  bDeviceClass          255 Vendor Specific Class
  bDeviceSubClass         0 
  bDeviceProtocol         0 
  bMaxPacketSize0         8
  idVendor           0x16c0 Van Ooijen Technische Informatica
  idProduct          0x05dc shared ID for use with libusb
  bcdDevice            1.02
  iManufacturer           1 www.anyma.ch
  iProduct                2 uDMX
  iSerial                 3 ilLUTZminator001
  bNumConfigurations      1
  Configuration Descriptor:
    bLength                 9
    bDescriptorType         2
    wTotalLength           18
    bNumInterfaces          1
    bConfigurationValue     1
    iConfiguration          0 
    bmAttributes         0x80
      (Bus Powered)
    MaxPower              500mA
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        0
      bAlternateSetting       0
      bNumEndpoints           0
      bInterfaceClass         0 (Defined at Interface level)
      bInterfaceSubClass      0 
      bInterfaceProtocol      0 
      iInterface              0 
Device Status:     0x0000
  (Bus Powered)

References

1. uDMX - tiny bus powered USB-DMX interface - Anyma
2. illutzminator
3. Markus Baertschi uDMX Utility
4. Writing udev rules
5. PyUSB