I saw this mentioned here, but it would be great to have USB 3.0 support in the next version. I just ran into an issue where the Joulescope would cause a bandwidth limitation crash in the Saleae when connected to the same hub. Unfortunately, it pipes everything through the same USB 2.0 hub tree, causing the bottleneck.
I know it’s a big ask, but it would be great!
Hi @sethk - We are already working on the third-generation Joulescope JS320. It will also use USB 2 high-speed (480 MHz). We did consider USB superspeed 5 GHz with the new Infineon (formerly Cypress) FX5, but the cost add was significant compared to USB high-speed. Since Joulescopes only require about 10 MB/s, it is hard to justify a significant price increase for USB 3.
USB high-speed, full-speed, and low-speed devices are essentially on the same “shared bus” topology, where data transmission is explicitly initiated by the host. That’s just how USB 1 & 2 have worked for decades. The downside is that any device on the same root hub can reduce the amount of throughput available for other devices. While I would love Joulescopes to use USB isochronous mode, I also consider USB 2 isochronous mode to be fundamentally flawed.
USB 3 is really an entirely separate bus from USB 1 & 2 with it’s own differential pairs and signaling. The USB-IF definitely has challenges communicating port capabilities with USB 2 480 MHz, 5 GHz, 10 GHz, 20 GHz, 40 GHz, different power ratings, PPS, source/sink, battery charging, and more. That said, USB is still the easiest and most ubiquitous way to connect a peripheral to a host computer.
If you have a desktop host computer, you can add additional USB root hubs using PCIe to USB cards.
Yeah, that’s totally fair.
This is an understatement!
Unfortunately, I’m running a laptop with a dock. Thankfully, the laptop itself has 3 USB-C 3.0 ports, so I have some options when it comes to connecting. However, that defeats the whole intention behind the dock (but that’s my issue and not something Joulescope specific).
@sethk - Does the laptop have Thunderbolt? If so, then you can get a Thunderbolt dock (using PCIe) that adds more USB root hubs. You can also consider a Thunderbolt to PCIe card expander, such as the OWC Mercury Helios 3S. You can then add a PCIe to USB expansion card.
So my laptop has a Thunderbolt port, but I’m trying to minimize the number of cables I need to connect to it, which is why I got a dock. (I’m actually not sure which of the 3 USB ports is the Thunderbolt port, as the dock supposedly uses Thunderbolt and works just fine on all 3 ports….)
I’m able to solve the problem with a second USB-C cable directly to the laptop, so it’s equally inconvenient as the Thunderbolt to PCIe card expander in this case. However, I will definitely keep that in mind for my next laptop purchase (or move to desktop where I have easy expandability).
Thanks for the info and answer.