USB differential routing help

雨亭婉清

USB differential routing help [Copy link]

Please help me check the USB differential routing. The Android end cannot receive data.

雨亭婉清

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chunyang

Non-compliant differential lines will only cause bit error rate problems at high speeds, and will not cause communication failures. Obviously, there is something else wrong with your system.

le062

Why do we need to add a 47pF capacitor to ground? Why?

雨亭婉清

le062 posted on 2018-5-29 13:34 Why do we need to add a 47pF ground capacitor? Why?

The circuit recommended in the ft312d chip manual

雨亭婉清

chunyang posted on 2018-5-29 13:30 Non-compliant differential lines will only cause bit error rate problems at high speeds, and will not cause communication failures. Obviously, there are other problems with your system.

I am using the ft312d chip, and have connected pin 8 test1 to low and pin 9 test2 to high, but the common mode voltage of the differential is 0, and communication is still not possible. What else could be the problem?

le062

I looked at the chip data and it's just a full-speed 12M signal. If you draw a circle around the two lines, it probably won't affect the USB communication.

chunyang

Yuting Wanqing posted on 2018-5-29 13:55 I am using the ft312d chip. I have connected the 8th pin test1 to low and the 9th pin test2 to high, but the differential common mode voltage is 0, and communication is still not possible. Also...

I suggest you read the device manual carefully and check whether the actual circuit is strictly consistent with the device manual. At the same time, pay attention to the welding problem.

雨亭婉清

The problem is solved. It turns out that the external connection cables have sequence requirements, and the OTG connection cable requires a master device.