Join us in Chat. Click link in menu bar to join. Unofficial chat day is every Friday night (US time).
0 Members and 1 Guest are viewing this topic.
It sounds like you have configured the CP2102 in a "Bus-Powered" configuration. This will power the CP2102 only when the USB is connected.To use the CP2102 on-chip regulator to get 3.3V when USB is not connected, you should connect the CP2102 in the "Self-Powered" configuration shown in Fig 8 of the CP2102 datasheet. In this config, the CP2102 will continue to generate 3.3V even when USB is not connected using your on-board 5.3V source (connected to REGIN pin). You don't need to generate any special reset on connection to USB because the CP2102 can detect USB connection using the VBUS pin. Note that the on-chip regulator can supply a maximum of 100 mA current at 3.3V. This includes the ~27mA current needed by the CP2102 itself. So, your board can only draw ~73mA or less from the CP2102 to stay within specifications. If more current is needed by your board, an external voltage regulator should be used instead.
Oh and I used the recommended .1uF instead of .01uF cap that you used (why did you use the lower cap?).
The USB max power and power attributes descriptor must match the device power usage and configuration. See application note “AN144: CP210x Customization Guide” for information on how to customize USB descriptors for the CP2102.
I apologize for the delayed response. I'm glad you were able to find the source of the problem and fix it. With the default MaxPower values, the CP2102 should work in self-powered mode even if the you have not reprogrammed the device to be self-powered using the AN144 software. The "self-powered" check box only alters a value in the USB descriptor that lets the host know that the CP2102 won't need any power from the host. Please let me know if you have any other questions.