A reel of ADuM4160s
I’m pleased to announce that the long wait is finally over – I’m now in possession of a reel (this is 1000 pcs!) of ADuM4160 – the core chip of USB Isolator
. I will be shipping back orders today and tomorrow – if you have ordered any of USB Isolator products from me in February, March, or April, and will not have gotten shipping notification by Monday, please contact me.
USB Isolators are back in stock. By popular demand, I also started selling ADuM4160 in single quantities – look in components section of the store.
On a side note, I received an e-mail from a company in Denmark offering ADuM4160-based USB Isolators in “complete” form – sporting a nice looking case and bus-powered supply for the peripheral side. I bought one yesterday to take a look. I’m going to write a review and, if I like it, start reselling it.
USB A to B connectors back to back
USB isolation is good for you. Isolated DAC makes better sound, isolated oscilloscope produces cleaner trace, and making line voltage measurements with isolated instruments helps us live longer. However, USB isolation often comes with a cost of extra USB cable, which may become excessive if we take into account precious desk space taken by said cable, as well as time spent on finding and untangling it.
I made several attempts to build a short cable which would also be able to bear load of USB isolator. Finally, while searching for a source of PCB mounted USB male B-type connector, I found this little marvel on eBay.
There is not much to say about it. It is short rigid adapter with USB A-type connector on one end and B-type on the other. The following picture shows typical arrangement – USB isolator connected to my Bitscope with USB adapter holding isolator in the air.
Of course, this little adapter can be used for connecting many other devices. Another picture shows our beloved Arduino connected to a USB port of a laptop computer. Here the weak spot of the adapter is clearly seen – since A and B connectors are turned 180 degrees, connected device would be turned upside down. For isolator it doesn’t matter much; however, operating Arduino’s Reset button and connecting shields would be difficult.
Adapter is available from several sources on eBay. Prices vary from $0.90 to $2.00, often with free shipping. The search string is “USB 2.0 Male to Printer Scanner A-B Converter Adapter”. Enjoy!
USB Isolator connected to Bitscope using short cable
Using USB adapter to connect Arduino to a PC
ADuM4160 PIN pin grounding
Q. I am getting “USB device not recognized” error message – what do I do? Also, since the isolator is soldered into my circuit, “reconnect peripheral” suggestion seems too difficult to follow.
I decided to write this article after receiving several e-mails from people who bought my isolator. While setups described in those e-mails were different, the problem was the same – a PC refusing to recognize the device connected through the isolator. Here I will try to explain what is happening and also share my ideas how to troubleshoot and possibly fix the problem.
When nothing is connected to USB port, the bus is held at ground level with pull down resistors on the host side. USB device, when connected, pulls one of bus lines up, often times also with a resistor connected to Vbus and data line. Host sees it, sends bus reset and tries to query the device. If device is answering, host keeps querying the device and eventually enumerates it. When device is enumerated, application takes over.
If device is not answering (like for example, when self-powered device is turned off), host will give up and post “Device not recognized” message. To get attention from the host, we need to generate bus event, i.e., disconnect the peripheral and connect it back again.
Continue reading USB Isolator Most Frequently Asked Question
USB Isolator Board Solder Stencil
I received a batch of solder paste stencils for my USB Isolator PCB. Now those who want to try low-tech reflow soldering technique, can do it. Stencils are laser cut by Ohararp from 0.0035″ Kapton. They are now offered for sale at the store.
USB Isolator parts
Immediately after announcing USB Isolator circuit I received several suggestions to put together a parts kit. Indeed, users of such devices are usually not afraid of small parts and generally aware of which side of soldering iron is better suited for holding on to. Also, I’m having hard time trying to find a supplier, where one can buy all the parts to build this circuit; usually, you need to buy from 2-3 suppliers, which significantly adds to shipping expenses. Considering this, I’m now offering not one, but two parts kits to build an USB Isolator based on Analog Devices’ ADuM4160.
The kits are added to “ADuM4160 USB Isolator bare PCB and kits” dropdown. One kit contains all the parts necessary to build an isolator – PCB, ADum4160, capacitors, resistors, USB connectors, pin headers, and jumpers and costs $25. Another kits contains all that plus all parts for 5V buck converter – LT1376-5, inductor, caps, etc and costs $33. Enjoy!
I’m not writing a build manual at this time; I’d like to get some feedback from builders first. Any questions you have, please don’t hesitate to ask.
ADuM4160 USB Isolator PCB panel
USB Isolator PCBs has arrived. In this article I will be talking about building and configuring one. The PCB was designed with hobbyist-friendly large size SMD packages and 10mil clearances and I hope it won’t be difficult to made one at home. The layout files are available from downloads section.
Let’s talk about parts procurement. This is a BOM at Mouser sans ADuM4160, LT1376-5, and PCB. This is BOM at Digi-Key, which includes LT1376-5. Last time I checked, Digi-Key was way more expensive. As far as ADuM4160, since no one sells it in single quantities right now (check this using FindChips), the easiest way to get it is to ask Analog Devices for a sample, they are generous folks.
Continue reading Building USB Isolator.
[ Update ] I now have bare PCBs and parts kits of this design for sale in store, as well as assembled and tested boards.
We all love USB. It is well supported across many platforms, easy to work with, and even able to provide a little power to the peripheral. However, the quirk of USB is that peripheral must share ground line with the host. The host is usually a PC and very often a desktop, which means it’s USB ground is electrically connected to earth ground in the wall outlet. With PC-based test instruments, like oscilloscopes, logic analyzers and such, It works fine most of the time, but not always.
There are situations when we prefer our ground separate. It happens when PC/earth ground is too “dirty” and we don’t want our circuit to pick up this dirt. Sometimes our device’s ground is not too good or even dangerous if connected to earth ground. Sometimes we are trying to overcome ground loops. Sometimes, we want our oscilloscope to behave like a multimeter, i.e. being able to show voltage drop between any two arbitrary points of the circuit. In any of this cases we want our USB data and ground isolated from the host.
Isolation improves common-mode voltage, enhances noise rejection, and permits two circuits to operate at different voltage levels. It also tends to save test equipment, as well as PC itself. It is also very useful in industrial setting, that probably why industrial USB isolator devices cost between $200 and $400. While looking for a solution for my lab, I found interesting USB isolator part, recently released by Analog Devices, and decided to give it a try.
Continue reading USB Isolator.