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.
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. However, when host and peripheral are talking through ADuM4160, this is not always the case. 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.
It is possible to simulate device disconnect without breaking actual connection by pulling PIN pin of ADuM4160 to ground. Normally it is held at 5V by R8 pull up resistor. This resistor is located next to peripheral side USB connector and marked 1M above it. Left side of it, the one right below the “1M” mark is connected to PIN pin (12). The closest ground point is right pad of bypass capacitor, which sits above R8. An experimenter with good eyesight and steady hand can easily connect those two points with tweezers. However, if said experimenter is not feeling comfortable operating tweezers inside powered circuit, a safer arrangement is shown on the title picture.
Disconnecting peripheral, either directly or by driving PIN pin, with power applied to the isolator and host side connected, will most likely solve device detection problem. If you still having issues with the circuit, please let me know, I will try to help.
Oleg.
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Dear Oleg,
Your PIN advice works great. I installed a toggle switch between ground and R8 that allows me for “re-boot” the connection in case of accidental disconnection. I use your isolator on my USB audio DACs. I strongly recommend it for this purpose as the improvement in sound quality is evident.
Many thanks fro your help.
PS: a remark; I read 3.3VDC at R8 (not 5VDC) as it is connected to VDD2…
Thank you for the catch – I’ll make corrections to the article!
hi Oleg,
the board works great with a mice in low speed mode
in fast speed mode i get only the USB device not recognized error.
I try to use an usbasp Adapter , no way, not slow or fast.
I get only USB device not recognized. :-(
regards from Germany
Uwe
From what I can see, USBasp should be compatible with this isolator. Have you tried other high-speed devices, like usb flash drive, for example?
Also, tell me about your power supply – can you measure 5volts with USBasp connected?
Hi Oleg,
I have power off my Laptop, not only a reboot.
Now i works well, in fast mode and with usbasp!
A good job….
regards from Germany
Uwe
I’m glad you got it running; however, powering the isolator from a computer is wrong. It might work but it won’t isolate. You need to use separate power supply fro peripheral side.
Hi,
Have you tested your USB Isolator with external 2.5inch portal hard drives?
Thanks
I haven’t tested it with 2.5 drives. It works fine with 3.5 external drives. What is the difference?
Hi,
I made my own circuit using this device, but it works fine on some PC’s, but on other PC’s it says, “USB device not recognized”. What do you think could be the problem?
I have pins 3,4,5 connected together and then on the other side, 12,13,14 are connected together. I am also using 24R on both sides for the D+ and D- lines.
Best Regards,
Ray
I am not using 1meg pullups or any pullups, just connecting them directly.
The circuit works on one PC, but on others there is the not recognized problem.
Have you tried grounding PIN pin as in the article (to do this, you will need a pullup on it)?