Hey everyone, I recently have been messing around with some USB stuff and thought it would be fun to try to read and decode the USB packets that for example my keyboard sends to my PC. Now ive messed around a bit but after a number of failed attempts (receiving nothing but the idle state when reading the data lines of the USB cable) I found out that the signals are way too fast for my arduino nano to measure, Ive bought and hooked up a cheap logic analyzer which could capture some packets when recording at 24MHz but not with nearly enough detail. Now i did some research and figured out that i would need to be sampling the data signals at around or above 50MHZ. Obviously this wont be possible with just an arduino as its not nearly fast enough. Is there a way to read these packets using some sort of chip perhaps? (seeing as the packets are only being sent every millisecond maybe some chip could read them and store them so the arduino can request them since it would be fast enough to do that every millisecond) Or is it just not possible with an arduino?
You will need a much faster logic analyzer to decode USB transmissions.
Im trying to do it programmatically though, a 24MHz logic analyzer showed me that there were packets being sent, it was not able to properly decode them but it showed a packet every millisecond
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I am not looking for a logic analyzer, im asking if its possible to read these packets using an arduino and potentially some extra hardware and if so, how
You might be able to do this with the PCJR 600 MHz Teensy 4.0 or 4.1.
It looks like a faster arduino, is that correct and does that mean i can just write my code for that and read the signals that way? and is it fast enough to read full speed usb?
The Teensy runs standard Arduino code.
For signal analysis, people generally recommend to sample at 10X the frequency of interest, minimum.
I'll give it a try, thanks a lot!
I could not find any USB protocol analyzer, only USB based or powered analyzers.
A solution should include a line receiver for USB (differential) signals and DMA for fast storage. Analog (ADC) recording is not required for tracing the digital USB bus.
In theory, most keyboards use "low speed" USB that an AVR can just barely read (which is how things like a DigiSpark or the USPASP programmers manage to speak USB without any hardware support.)
(that's "historically" - it may be that modern keyboards use "full speed" USB connections.)
Yes... You can also "just write" your thesis and win Nobel prize...