Posted on January 25, 2017 at 14:23Hi Dani. The referenced controller from Asix is the leading USB3.1 to Gigabit bridge device on the market. You will need to decide the best route based on your specifications.
1) Is your USB interface operating at USB 3.1 Gen 1 (aka USB 3.0) ? USB 2.0 HS ? USB 2.0 FS ? If you are operating at USB 2.0 then the respective bridge controller should also be a USB 2.0 as a cost reduction. Please review the datasheets for each such controller to understand if any other improvements have been made between the silicon (ie. bug fixes, larger ethernet frames, etc.). If the project can justify the expense then consider to use the more current USB3.1 controller.
2) Industrial use - how noisy / harsh is the environment ? For our designs, we like to throw in the kitchen sink with hope that the end customer will only contact us with new purchase orders. The off-the-shelf dongles will be basic designs to lower the end product cost. Recommend that you source a few to inspect and then if it makes sense, to design your own robust version. For example, apply nice ESD protection and Vbus protection onto the USB lines. Many offshore dongles do not offer such level of protection. In theory, the first USB port that interfaces with the host PC will see the ESD surges so you can decide where to apply the protection. That is, if you have a USB hub then the upstream port will feature the ESD protection but in theory, is not required on the downstream ports mating with your embebdded design.
Perhaps your project can demand and justify the use of USB isolators ? Analog is a popular choice for USB low and full speed (need a jumper to select the proper speed). A more current method is to use the Murata modules for USB isolation (again for USB low / full speed with auto-detect) so not for High Speed isolation. High Speed USB 2.0 (480 Mbps) isolation is possible but fairly high cost (see Silanna USB - single chip isolator is $50+ USD and also require an isolated DC-DC module).
Even the Ethernet port can face nasty ESD events so review the use of ST or similar Ethernet port protectors.
Again, highly unlikely that you will see this level of protection on a standard USB to Ethernet dongle. We are living in the land of disposable widgets which is not how we would design such products.
The dongle in your post is available for under $ 10 USD from China in a retail blister package.
The Asix controller is under $ 5 USD in sample quantity if you wish to spin your own version of such a design. Cypress is also in this range.
3) The use of mature Ethernet bridge devices is a practical idea due to the very high volume of consumption. You will also have support from the respective silicon vendor and can tweak the bill of materials to suit your specification. Unless you are following a reference design with your current approach, the smallest detail or tool chain issue can be real time killers. We came to ST after wasting weeks of long work days on another vendor's rapid GUI tool which is clearly broken. ST so far is solid with high potential but for us, lacking complete projects for our target CPU device(s). Our beef is that if we are to learn from examples and the vendor tools are broken then we are just spinning our wheels with little or no progress. Often documentation is not in sync with the kits or tools and even worse if the silicon has bugs that have not yet been resolved.
The best suggestion at this time is to review assorted dongles through Amazon or similar sourcing and then benchmark and study the insides of each product. If you find the dongle to be stable, then proceed to build your own robust version of the same. That would be our approach. Asix, Cypress, Exar each offer relatively low cost reference boards for such controllers for this exercise. In our opinion and from our experience, Asix & Exar are both excellent in tech support and then Cypress. Cypress wants to see high volume potential for proper support.
You noted:
I want to make a bridge from USB to Ethernet, to give connectivity to a tablet.
Will the tablet be the USB host ? Which operating system will be running on this tablet ? Be sure that the silicon vendor is able to support the respective USB to Ethernet bridge controller. You should be fine with any of these 3 vendors if using Windows, Linux or Android but do check to confirm the specific details.
