Adding Auto-Reset Pin to PL2303 Based Serial-USB Modules




About: Mechatronics Engineer . Hopeless Realist

I got a couple of cheap PL2303 based Serial to USB modules off AliExpress thinking they would work for uploading code on to my Arduino Pro Mini. Unfortunately, I later figured the modules didn't have a reset pin and everyone who's tried manual reset, knows it's a pain.

A quick look into the 2303 datasheet confirmed that the chip does have a pin dedicated for auto-reset and that it wasn't connected to anything on my modules. I gave it a try, pulling out the pin through a small capacitor and it worked!

Although, most of you hackers out there are more intimidated by SMD chips than a Trex running at you, this hack is rather easy, really.

Things you'll need:

  1. 47nF ceramic capacitor
  2. A hookup wire with a male/female header
  3. Micro solder iron
  4. Flux
  5. Desoldering wick
  6. Magnifying glass (optional)
  7. Heat shrink tube

Teacher Notes

Teachers! Did you use this instructable in your classroom?
Add a Teacher Note to share how you incorporated it into your lesson.

Step 1: Prep the Parts

Fortunately, my modules came with a SSOP28 package, I'd be damned if it were a QNF.

Rip the heat shrink if it came shrunk and locate Pin2 on the chip.

Take a 47nF ceramic capacitor, cut and bend one of its legs into a U-shape such that when the pin is soldered, the cap sits on the bottom side (or you can solder that cap in whatever way that pleases you).

Step 2: Set It Up

I used my helping hand to precisely align the capacitor leg on to Pin2 and then dab some flux on the pins before I soldered it. Don't really need a 3rd hand I guess, I used it because I don't have a steady enough hand for the job.

Step 3: Soldering

Gotta be a bit careful on this step, clean the solder tip, dip it in flux, melt on a small amount of solder on to the tip, just enough to tack on the capacitor to Pin2 and use a magnifying glass to inspect the joint, in case you're paranoid of a solder bridge.

Keep some desoldering wick on hand just in case you accidentally bridge the adjacent pins. I needed the wick thrice on hacking two modules.

On the flip-side, solder a small piece of wire with a male/female header on to the capacitor's free end and be sure to insulate it.

Step 4: Testing and Finishing Up

Hook up the module to a Pro Mini and upload the infamous Blink (or any other code!) to confirm that your module is working.

Finish off the hack with some nice heat shrink. I love them clear shrinks!

5 People Made This Project!


  • Made with Math Contest

    Made with Math Contest
  • Multi-Discipline Contest

    Multi-Discipline Contest
  • Robotics Contest

    Robotics Contest

5 Discussions


1 year ago

Many Thanks for the Pin instruction. I had this Problem.

Now, I did some upgrade to mine. I used the "3.3V pin" (useless for me) as "DTR pin".

No extra capacitor or hanging wires... Details in Pictures...


1 year ago

Watch out the chip, mine had a CH340G which has DTR on pin 13


2 years ago

Awesome hack !! :)
just would like to know, if i skip the capacitor and directly connect the pin would it be ok ?





3 years ago

Hello, please what type of programmer have I set in arduino IDE, to get pl2303 work as programmer??


4 years ago

I managed to convert mine just as described.
So thanks for that as trying to time pressing tge reset button was becoming tiresome!!