I want to connect an Arduino Pro Mini with ATmega328P so as to drive a SI4463. But I don't know BLK, CTS, DTR should be connected to what pins of ATmega328P.

How do I connect this?

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  • 1
    If you're trying to build an ATmega circuit and asking about it on the Arduino site, shouldn't you review the published schematic of a comparable Arduino, ie, one using the same 5-pin FTDI header??? Additionally you should probably consider prototyping this with a modular Arduino before making a board - the Si4463 is non-trivial in complexity even if on a module, and in addition to helping prove your plans, a prototype around an Arduino will let you get started on the software tasks while your PCB is being fabricated. Jun 7, 2018 at 17:03

1 Answer 1


BLK is ground.
CTS is generally not used. I leave it unconnected on my boards.
DTR goes to the auto-reset circuit.


Can I let DTR directly connect with RESET ?

Auto-reset circuits use a .1uf capacitor between the DTR (or RTS, depends on which one your cable supplies) and the reset pin. (The exact value probably isn't too important). Without it, the reset circuit is likely pick up noise and randomly reset the Arduino.

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  • Can I let DTR directly connect with RESET ?
    – Enhao Lan
    Jun 7, 2018 at 15:28
  • You can’t connect it directly, because it is low when a connection is made. So it will keep the Arduino in reset-mode all the time. So the bootloader will never run, and you can’t upload any new code or run existing code.
    – Gerben
    Jun 7, 2018 at 17:03
  • Also a good idea to have a diode in parallel with the resistor - cathode to 5V. Keeps any high voltage spikes on the Reset line from kicking off the High Voltage programming sequence and the chip then acting hung.
    – CrossRoads
    Jun 7, 2018 at 17:59

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