We are using ADum3160 USB isolator in our design. When it is connected to PC it is not working and shows USB Device not Recognized. If we directly connect USB pins to our microcontroller it is working fine.
I would start by checking the the device being plugged in is the correct speed for the setting. It looks from your drawing that the port is set for full speed, so full and high speed devices will be recognized. A low speed device will not be recognized. Next, I don't see any bypass caps near the part. It is critical to provide bypass on the Vbus and Vdd lines on both sides of the part. Also review the application of the pullup resistor by the peripheral. Some controllers need an external pullup.
Let me know how you are progressing.
Hello MS Cantrell,
Thank you for your immediate reply. For your better clarity I am uploading USB circuit and controller block diagram. Bellow is my reply for your
We are using PIC32.
Please let me know your suggestion for debugging or any issue in our circuit.
Everything you have supplied looks like you are using the part correctly. This should work.
I think it is time to go back to basics, and check the power supply voltages are correct right at the pins and be sure that the enumeration signals are making it in and out of the isolator, and that there is not voltage contention due to outputs fighting for the bus. Voltages on the D+and D- lines should be close to GND and 3.3V on both sides of the isolator. Last time a customer had a similar issue, it turned out to be a cracked trace on the PCB.
A good test would be to use one of our USB evaluation boards and cable it in between your device with a direct connection and the computer. If that works, then the issue is with the PCB.
Let me know what you find out.
Hi MS Cantrell,
Thank you for your valuable inputs. Yes your right USB isolator circuit has no issue in our board. To test USB isolator alnoe in the board,
With above modifications Mouse is able to operate through the isolator which is connected to the PC.
But when down stream side is connected to the PIC32 then PC is not able to recognize the USB.
Did you change the SPU and SPD pins when you connected to the PIC?
It was setted for Low speed operation to connect mouse ,
down stream D+,D- series resistors were removed
Up stream : PC
Down stream: Mouse
With the above values mouse is working through USB isolator which is connected to PC.
Then down stream D+,D- series resistors are mounted (0 ohm, upstream also 0 ohm) to connect PIC32. And low speed code (sample code from microchip) was flashed and checked but it was not able to recognize.
El mensaje fue editado por: saravanakumar samudi
Have you checked the idle state on each side of the isolator. Idle should be D- high and D+ low. If that is not the idle state, then check the state of the PIC pullup.
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