I know this that when you try to program a pro mini without a DTR pin it will give you a error as the atmega needs to be reset during programming. So I had a doubt why does the microcontroller needs to be reset and clearly at which time you know at which moment does it reset ?

1 Answer 1


A Reset is necessary to activate the Bootloader and allow programming. Without the DTR signal the Reset button has to be pressed just before starting the upload from the Arduino IDE.

  • Is there any serial traffic before upload or is there anything like that the compiler sends any notification to the device. Commented Apr 30, 2017 at 10:39
  • The compiler does not know about the upload. It is avrdude that does the upload. The reset is generated by pulling the DTR signal. Please see playground.arduino.cc/Learning/AutoResetRetrofit for more information about the auto-reset feature. Commented Apr 30, 2017 at 10:44
  • If the software is somehow unable to send the reset signal then how could I create reset signal without manually pressing the reset button. Commented Apr 30, 2017 at 10:51
  • What FTDI (USB-Serial bridge) are you using? Does it lack a DTR pin? Commented Apr 30, 2017 at 11:03
  • Actually I don't really have a DTR pin I have only TX RX and GND pin. Commented Apr 30, 2017 at 11:35

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