I’ve got my Fez Cerb 40 II up and running, but I have some questions as the site information isn’t perfectly clear to me and the documentation mainly represents the the Non II model. First version (without the 3.3 volt regulator and RTC crystal)
Anyway, It seems to power itself via the USB and enable debugging, etc without any addition power sources, but the documentation does not mention anything about this. Also, I’m interested in powering other devices that will work in with the Cerb.
Anyway here are my questions/ clarifications on some of the Pins and the capabilities/should/should nots
Pin: USB - 5V from the USB port. (Also Input VCC from a power supply if USB is not present?)
Pin: 3.3v - Regulated down from USB pin from 5v to 3.3v. This also powers the device. OUTPUT.
Vbat - only to power the RTC crystal when there is no power.
That all being said, When USB in not present, USB pin is the power in? Off the cuff, would a simple LM7805 regulator circuit be sufficient to power the device and some other small ICs and LEDs?
OR do I really need an external regulated power supply while USB is present?
Any clarification/corrections on the above is appreciated