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11 years, 1 month ago.
USB HID speed
What determines the overall speed of the USBHID?
I am looking to send files and doing some tests to see how fast I can get reports back and forth. Is there a baudrate or limitation of some kind? It seems quite slow. Yet obviously USBMSD can transfer files back and forth very quickly?
What is the limitation? fyi I am on KL25Z and using the USBHID testcase.
2 Answers
10 years, 9 months ago.
Thats what I would like to know also. Even I didn't get any answer to my question " how to speed up the Ethernet connection / shorten the transmission latency". I guess mbed.org has no idea or they don't want to communicate the "weak spot of this technology". Am I wrong? Have you searched for the complete mbed library source in assembler? Did you find something suitable? You are waiting now for almost 4 months, and there is no comment. Really pity.
Please let me know if you have any solution. I'm searching still for a fast data transmission using mbed. But: there are some alternatives (more expensive). Regards, Georg
10 years, 9 months ago.
There's a lot of variables to consider. For USB, transactions are done on a 1ms timer on the host. Depending on what mode, drivers and operating system let alone other devices on the USB will have an effect. There are free USB sniffers that will give an idea of what is happening on the bus.
Similarly for Ethernet - what are we talking about here? Ethernet itself or tcp/ip over Ethernet? There are many points of latency. Again, there are free tools like Wireshark that let you see what is happening on the network to better understand what is happening and when. You can use this information to formulate tests to see where the slowdown is happening. If you use UDP, there's little in the way to slow things down, except, Windows. See how fast you can pump out UDP packets via MBED.
As for 'weak spot of this technology' - I'd suggest you get some evidence first. Are the MBED libraries any faster or slower than anything else comparable? For the most part, there isn't any magic. I'm sure if you post a concise question with some evidence, you'll get a useful answer.
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posted by tap tap 21 Jun 2013