I am building a small li-ion powered flashlight/laser with a 4 digit display. I have a charger fitted into the flashlight body so that the micro usb-b port is easy to use. The port has five terminals soldered to the board but only utilizes two, 5v and gnd. I will be using an atmega 328 chip to monitor and control everything. All the pins are in use, d0 and d1 are driving two segments of the display at 5v.
I want one port. I want to plug into any usb and charge. I want to plug into a special homemade cable to reprogram. And I don’t care if the display looks funny while it is connected.
I don’t want two ports. I don’t want to harm the chip or my computer. And I don’t want to reduce the charge output too low somehow (I think that has to do with the usb id pin4?).
What will happen if I connect the rx tx pins to the usb port and plug it into a computer while the segments are illuminating?
What size resistors should be in series between the pins and the port? (The common side of each segment is 470 ohms to gnd.)
What size resistor if any should be connected between the id pin and gnd?