If I use the U2D2 to communicate with my Dynamixel XL330-M288 from my macbook (macos) I always have a latency of over 15ms for reading the current position or setting the goal position for example. I am using Python.
If I use the FE-URT-1 USB to TTL (https://www.robotshop.com/products/fe-urt-1-usb-to-ttl-485-bus-programmer) I have a latency of just over 1ms with python on my macbook. What is the reason for the large latency with the U2D2?
The latency timer issue is from the USB standard and not from the U2D2 per se. I don’t use Mac OS so I do not know where to change it at the OS level. On Windows machines I used Device Manager to change all that. Are you using the DXL SDK? You’ll need to change it with the new timer value too.
I am using the dynamixel-sdk from pypi.
Why do I have a much lower latency with the FE-URT-1 USB to TTL board instead of the U2D2. I tested it with the same macbook, python program and servo motor. I have only exchanged the U2D2 with the FE-URT-1 board.
Did you really read my last post? And check out that link that shows you how to change the timer setting inside the file port_handler.py?
yes, I read your last post. You can’t change the usb device properties in macos. Changing the LATENCY_TIMER does not improve the latency at all. I think it has to be a problem with the U2D2 board since the FE-URT-1 USB to TTL converter works fine.
Interesting! I have modified the Latency Timer to 1 ms in Windows PCs and Linux SBCs such as RPi and Jetson, and the U2D2 works fine at these settings - I had to change this setting at the OS level and also recompiled my DXL SDK library with this setting. Perhaps with Macs the user better use the FE-URT-1 USB to TTL converter. That is good to know.
Do you happen to be on one of the newer Mac’s utilizing Apple’s new M1 or 2 chips? If so, the reason for the latency is due to the fact that the drivers we use for the U2D2 haven’t been recertified by Apple for permissions to use high speed USB serial communications.
If you aren’t experiencing these issues with your alternative USB to serial adapter, you can feel free to use that to control your DYNAMIXELS instead.
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Yes, I am using a Macbook Air M1. That is very unfortunate. It does work with my other USB to serial adaptaper. But the cabling is very messy and I am unable to buy more of those adapters. When do you think the U2D2 will be certified for high speed USB by Apple?
AliExpress sells this one “USB2TDXL”, claiming to be OK for MACs, but I have never tried it: