An experimenter with good eyesight and steady hand can easily connect those two points with tweezers. The closest ground point is right pad of bypass capacitor, which sits above R8. ![]() Left side of it, the one right below the “1M” mark is connected to PIN pin (12). This resistor is located next to peripheral side USB connector and marked 1M above it. Normally it is held at 5V by R8 pull up resistor. It is possible to simulate device disconnect without breaking actual connection by pulling PIN pin of ADuM4160 to ground. I tested about 50 different USB devices and found out that while breaking the connection on the peripheral side works every time, host side disconnect does or does not help depending on device. However, when host and peripheral are talking through ADuM4160, this is not always the case. If we are dealing with typical copper-wire-connected USB host and peripheral, which end of USB cable gets disconnected and reconnected would not matter. To get attention from the host, we need to generate bus event, i.e., disconnect the peripheral and connect it back again. 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. When device is enumerated, application takes over. If device is answering, host keeps querying the device and eventually enumerates it. Host sees it, sends bus reset and tries to query the device. USB device, when connected, pulls one of bus lines up, often times also with a resistor connected to Vbus and data line. When nothing is connected to USB port, the bus is held at ground level with pull down resistors on the host side. Here I will try to explain what is happening and also share my ideas how to troubleshoot and possibly fix the problem. 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. ![]() I decided to write this article after receiving several e-mails from people who bought my isolator. 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. Making boards hackable for people who know what they're doing outside that range is still a design goal, but it's lower on our list of priorities.ADuM4160 PIN pin grounding Q. If we can simplify a layout or save board area by taking advantage of those rules, we will. Our design rules will always be for operation at 24v or less though, and mostly in the 0v-5v range. We respect the freedom of our peers to do the same, and try not to deliberately sabotage designs to make them unhackable. We accept responsibility for that risk though, and we know how to manage it. ![]() as hardware hackers we're all about voiding warranties, modifying devices, and using them at our own risk. In some cases, a person with appropriate experience will find it easy to modify one of our boards to operate way outside its nominal range, but that's an at-your-own-risk thing. We do have more training than our average customer though, and we make a lot of tools for ourselves. A board that can work safely in a high voltage environment doesn't, by itself, make working with high voltage safe, so our official stance is, "if you don't already know how to do it safely, don't do it at all until you've had proper training." Our overall goal is to be beginner friendly, and we have to be mindful of the people who don't know what they don't know. Officially, the board is only sold for 5v operation.
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