I'm designing a circuit to program an atmega328p over USB that is digitally isolated with an ADUM1402.
Question 1: I see circuits with the FT232RL with DTR, RTS or both connected to the atmega reset pin (through a 100nF cap). What is the difference? currently I have them both connected with solder jumpers between the connections. Any problem in keeping it that way?
Question 2: Currently I have placed the 100nF cap and 10K pull-up behind the ADUM1402. Is this correct? I wasn't sure where to place the cap (before or after the isolator). Will the isolator cause any problems when avrdude/Arduino tries to reset the Atmega?
Question 1: I see circuits with the FT232RL with DTR, RTS or both connected to the atmega reset pin (through a 100nF cap). What is the difference? currently I have them both connected with solder jumpers between the connections. Any problem in keeping it that way?
The difference is the basic desire of designers to be inconsistent.
As shown, that could be a chip destroyer as it depends on what the software does. They’re both outputs so what happens if one is driven high and the other low? Poof goes the magic smoke. If you want either signal to be able to assert the reset, add a 1N4148 in series with each output. You might need a pull down resistor at the input to the ADUM1402 to avoid a floating input when both pins are low. What does the datasheet say about that? Same condition applies to the pin 6 left floating on your schematic.
Question 2: Currently I have placed the 100nF cap and 10K pull-up behind the ADUM1402. Is this correct? I wasn't sure where to place the cap (before or after the isolator). Will the isolator cause any problems when avrdude/Arduino tries to reset the Atmega?
Schematic is correct as shown. You want the rc network on the output.
OP’s schematic:
