ESP8266 Community Forum

- Sun Jun 21, 2015 7:30 pm #21160 I'm far from an electronic engineer. I was looking at this image found on the Github site:

https://github.com/esp8266/Arduino



And it shows not only a common ground between the power supply and the USB<->Serial but it also seems to show a shared power supply. Can anyone confirm this is correct? I would have assumed that they would have shared a common ground only?

Free ESP8266 book available for download here.

- Sun Jun 21, 2015 8:46 pm #21163 You should never directly connect voltage sources. So you answer actually depends on the USB serial adapter. You should only connect the VCC pins to each other, when the serial adapter is not powered by the USB port (most adapters are bus powered, however there might be exceptions).

- Mon Jun 22, 2015 1:14 pm #21250 Thanks Lethe,
From your response, I get the impression that for most USB serial adapters, one should not connect the voltage sources together. What I read from the schematic is that the illustration does seem to show them being connected. I'm wondering if we need to ask for a change to the schematic or a warning/description of what is meant/implied by connecting the two together? If, as I believe, a hobbyist like myself stumbled over this diagram, they would be inclined to wire the supplies together as described.

Free ESP8266 book available for download here.

- Mon Jun 22, 2015 2:21 pm #21264 I agree. The Vccs should not be connected together like that, if the USB/TTL adapter has voltage output.