CM108B recognition issue and infor missing issue
We met 2 problems with CM108B
- After power ON/OFF for many
times, the gateway can not recognize the USB device.
- USB DP has a 1.5k pull up in our design. USB DM is also high during power ON.
- When I add a 1.5k pull down to USB DM , USB DM goes to low during power ON. Then the device can be recognized. Why does this happen?
- When the device is recognized by the gateway. The information from USB device is not correct for the 1st time. Some data is missing. And the data is complete at the 2nd time.
Gateway information :
- H38WL using Allwinner H3: Linux 3.4 ;
- H80WL using Allwinner H6 :Linux 3.10;
- Orangepi Lite H6 is the same, using Linux 4.9
22:20 Last Reply
Hi Tiger.luo:
CM108B IC has built-in 1.5k ohm pull-up, please remove the external 1.5k ohm and test again.
Thanks & B.R.
Jack
Dear Jack:
OK. I will remove the 1.5K resisitor and try again. But why an aditional 1.5K resisitor on DP can pullup the DM?
Hi Tiger.luo:
According to the USB specification, the Full Speed device must have a pull-up 1.5k ohm on DP, and DM does not need to do any actions on the circuit. "DM pull down" does not meet USB specification, we can't predict what will happen. Thanks.
Jack
Dear Jack:
Thanks for reminding. We are doing the test now ( without pullup and pulldown on DP & DM, use CM108B internal pullup )
Could you please help us analysis the data missing issue? 18 bytes data only got 8 bytes. When 1st time send the command " Get Descriptor" ,we can not get full data. Please see JPG for detail.
The CM108B uses the USB differential pair signals (USB DP and USB DM) for communication. The pull-up and pull-down resistors on these lines can affect signal integrity and device recognition. geometry dash subzero is an example. In standard USB implementations, USB DP should have a pull-up resistor (typically 1.5kΩ) to a voltage level of 3.3V or 5V. USB DM should not have a pull-down resistor. If adding a pull-down resistor to USB DM resolves the recognition issue, it suggests a potential signal integrity issue or a non-standard USB configuration in your system. Double-check your PCB layout, USB connector, and wiring for any potential issues or deviations from the standard USB specifications.
You can try bellow: 1. Power Cycling 2. USB DP Level 3. USB DM Pull-down 4. USB Device Communication 5. Firmware/Driver Updates If these solutions do not resolve the issues, it may be helpful to consult the CM108B manufacturer's technical support or seek assistance from an experienced electronics engineer for further troubleshooting and guidance. I had the same problem with the time card calculator.
I hope that you can quickly fix the problems you are having with this system. slope
If the issues persist, consider reaching out to the manufacturer's support for assistance. They may be able to provide specific guidance based on your device and setup. It's important to note that specific troubleshooting steps can vary based on the operating system, software, and use case. If you can provide more details about the nature of the recognition and missing information issues or the specific context in which you're using the CM108B, I may be able to offer more targeted assistance.
Ereyca: Kitchen Renovations Parramatta
I tried several ways and it connections worked
The USB enumeration process may be incomplete during the first pizza tower recognition. Check the enumeration process in the firmware to ensure it waits for the CM108B to complete enumeration before attempting to communicate.
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