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How do I connect the cables in order to program the Arduino 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.

CP2102 and Pro Mini

When I try cables like this:

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

The board lights up and green starts blinking, this should be the default blinker program.

I clicked 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.

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4 Answers 4

Reset to default
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Here's what works for me:

Pro Mini  ---------   CP2102

  DTR     ---------    DTR
  RST     ---------    RST   (optional if you wish to press some buttons)

  GND     ---------    GND
  RX      ---------    TX
  TX      ---------    RX
  VCC     ---------    VCC

Tap on the image to see the HD image

https://i.sstatic.net/NYENt.jpg https://i.sstatic.net/UVkNp.jpg

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I think the connections are alright, to upload the code you dont need to connect other than tx rx rst and power pins. Looking at your issue, I think it may be the on the software side. Please check if you have right drivers installed.

avrdude: stk500_recv(): programmer is not responding

Also, the issue can be resolved by changing the processor in Arduino software by going to tools->processor and then changing it to the one with the old bootloader.

Attaching a screenshot for reference: screenshot from arduino

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

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

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6
  • same errors, I tried the DTR and RTS pins from USB to pins from pro mini (RST, BLK) in all combinations. Commented Jul 25, 2019 at 13:17
  • You meant to add a 10K resistor ? Commented 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 Commented Jul 25, 2019 at 14:10
  • Are you positive your Promini has a bootloader installed? Commented 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 ? Commented Jul 25, 2019 at 14:12

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