How to connect the cables in order to program the pro mini with the CP2102 usb interface ? The TX RX and GND is easy, but I am not sure about the RST, DTR, DST, etc I attached the images of both.

enter image description here

EDIT: When I try cables like this:

TX  ... RX
RX  ... TX
5V  ... VCC // my pro mini is 5V version

The board lits up and green starts blinking, this should be the default blinker program. I click upload, I get this error, and I assume the cables are not properly connected:

avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x89
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 2 of 10: not in sync: resp=0x89

I know some people mentioned it works by adding some resistor and capacitor, but I was hoping that is an error and it should work without that complication.

2 Answers 2


RST to RST. Ignore the others, they are irrelevant.

  • 1
    Doesn't seem to work, I updated my questions with error details.
    – adrianTNT
    Jul 25, 2019 at 12:47

Pretty sure RST is Reset input to the CP2102, that will not work.

DTR to DTR (BLK on the Promini) will work, the DTR Low level goes thru the Promini's 0.1uF cap and 10K Reset pullup resistor to make a Reset pulse. That's how the FTDI Basic works when connected.

RTS (Request To Send output) might also work, that is supposedly a pulsed level.

  • same errors, I tried the DTR and RTS pins from USB to pins from pro mini (RST, BLK) in all combinations.
    – adrianTNT
    Jul 25, 2019 at 13:17
  • You meant to add a 10K resistor ?
    – adrianTNT
    Jul 25, 2019 at 13:19
  • The Promini's I've used store.yahoo.com/yhst-27389313707334/arpromi5v.html have the 0.1uF cap and 10K pullup resistor on board. All that was needed for programming was to connect an FTDI Basic directly to it, pin to pin. tinyosshop.com/download/Pro-Mini.sch.pdf
    – CrossRoads
    Jul 25, 2019 at 14:10
  • Are you positive your Promini has a bootloader installed?
    – CrossRoads
    Jul 25, 2019 at 14:11
  • I have no ideea, it seems to have blinker program installed, does it mean the bootloader is already there ?
    – adrianTNT
    Jul 25, 2019 at 14:12

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.