I am having trouble wrapping my brain around this. I have this generic FT232RL USB to UART Serial Adapter. Want to test my bootloader for loading firmware but have few questions.
Q.1 The DTR pin on these modules are suppose to be open drain and they are not connected to any pull up or pull down resistors (I checked). So according to my understanding open drain means the pin can only be in two states, ground or floating. So why pin is at 5V when I connect the module to PC?
Also connected a led to DTR pin it blinks as I toggle the pin from PC. This leads to my another question.
Q.2 So apparently DTR pin has 5V from the PC. The AVR is being powered from external 5V. Both devices ground are connected. To reset the AVR, we connect DTR pin to our AVR reset pin which is pulled up by a 10k resistor. So two different 5V sources will be connected to each other, won't this be a problem?
Q.3 The Tx and Rx lines, do they need any in series or pull up resistors? Considering the reset stage.
I am not using VCC and CTS pin of the module for any purpose.