usb2can-libusb driver for native 8devices CAN on OSX and other platforms #979
Conversation
Codecov Report
@@ Coverage Diff @@
## develop #979 +/- ##
===========================================
- Coverage 70.49% 70.24% -0.25%
===========================================
Files 79 83 +4
Lines 7679 7964 +285
===========================================
+ Hits 5413 5594 +181
- Misses 2266 2370 +104 |
|
Working on lint and docs as well of course :) |
| INSTALL | ||
| _______ | ||
|
|
||
| Install `pyusb` and a working pyusb backend (on most platforms, this is `libusb1`). |
There was a problem hiding this comment.
Lets add pyusb to the extras in setup.py
| raise ValueError( | ||
| "8Devices CAN interface not found! Serial number provided: %s" | ||
| % serial_number | ||
| ) |
There was a problem hiding this comment.
No worries with raising a value error here, but I'd like to give a backend specific exception to the user.
See #1046 (comment)
There was a problem hiding this comment.
By now, a CanInitializationError seems more appropriate.
| or self.data_rx_ep is None | ||
| or self.data_tx_ep is None | ||
| ): | ||
| raise ValueError("Could not configure 8Devices CAN endpoints!") |
There was a problem hiding this comment.
By now, a CanInitializationError seems more appropriate.
The USB2CAN from 8 devices https://www.8devices.com/products/usb2can originally has been built by Bernd Krumboeck here: But all these out-of-tree drivers are not really well maintained so I would suggest to look into the latest mainline Linux driver here: And you should make sure that the device has the latest v1.7 firmware as you might get problems when restarting the host with a powered USB-Hub otherwise. |
|
I checked the kernel in-tree driver, thanks for the link - it is a lot cleaner than the one in the 8devices repository. The overall message structure of course looks the same, but there are a few more error masks I may be able to use for some more specific backend errors (to the PR comments). So thank you for that! Unfortunately several features which the device seems to support via CANAL on Windows are still not documented/supported in any open source way- namely and particularly, message filtering, so that's a bit of a downer. That tangent aside, I will address the PR comments later this week. All seems good to address and perfectly reasonable to me - I see that after I asked about more specialized CAN errors, they were indeed added, so happy to support those. And I totally missed the setup.py extras! |
|
Ping As a note: Before merging this, the new exceptions should be used (see here). |
This is a very primitive/basic
pyusbbased native driver for the 8Devices USB2CAN hardware. The current 8Devices USB2CAN driver uses their "Canal" abstraction layer and is Windows-only.I tested this driver with a "Korlan USB2CAN" I purchased a few days ago, with firmware "2.3." My test harness is an M1 MacBook Air (OS X) performing ISO-TP communication (P2=0.05s) with an ECU CAN bus running at 500kbaud that spams around 300 messages/second, so the driver has been pretty well stress-tested and does seem viable for practical applications. Besides serial CAN, I think this is the first fully cross-platform (Linux, Windows, MacOS) driver, which is nice.
Unfortunately the 8Devices USB2CAN hardware is not well documented at all. So, this driver is based on the 8Devices Linux SocketCAN kernel module (https://github.com/8devices/usb2can/blob/master/usb_8dev.c) which, while it lives in the 8Devices GitHub organization, itself seems to have been based on a combination of private-thread email lore and reverse engineering.
I hope these tests are adequate. I tried to fence the USB part well enough to not require PyUSB for the test suite or on install.
The device does support a loopback mode that could be used to produce a hardware-in-the-loop integration test for owners of the hardware, although I didn't really see precedent for one in the codebase.
One thing I was uncertain of is the desired pattern for handling so-called "error frames." I just pass through the native device "error frames" as error frames directly to Python-CAN for now, which is what other devices seem to do as well.