Introduction: Adding Auto-Reset Pin to PL2303 Based Serial-USB Modules
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:
- 47nF ceramic capacitor
- A hookup wire with a male/female header
- Micro solder iron
- Desoldering wick
- Magnifying glass (optional)
- Heat shrink tube
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!
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