Why My First Custom PCB Became a $40 Drink Coaster

There is no feeling in the world quite like receiving a box from JLCPCB.

You open the package, pull out the glossy green fiberglass board, run your fingers over the HASL pads, and think: “I am Nikola Tesla. I have created hardware.”

Then you plug it in, and nothing happens. Zero. Not even a LED blink.

Welcome to the Hall of PCB Shame.

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💀 Mistake 1: The Classic RX/TX Swap

This is the rite of passage for every hardware engineer.

On your schematic:

• Microcontroller TX (Transmit) $⟶$ FTDI Serial Adapter TX (Transmit).
• Microcontroller RX (Receive) $⟶$ FTDI Serial Adapter RX (Receive).

Seems logical right? Connect TX to TX!

WRONG.

When you talk, you transmit ($TX$). When the other device listens, it receives ($RX$). Connecting $TX\to TX$ is like holding two telephones together ear-to-ear while both people scream into the air.

[WHAT I WIRED]:    MCU TX ──────────────> Serial TX  (Screaming into a speaker 📢)
                   MCU RX ──────────────> Serial RX  (Listening to a microphone 🎧)

[WHAT IT SHOULD BE]: MCU TX ───────────> Serial RX  (Talk to Listen 🗣️ 👂)

Fix: Had to physically scrape the copper traces off the board with an X-Acto knife and solder 38-gauge magnet wire cross-eyed under a microscope.

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💀 Mistake 2: The Decoupling Capacitor Massacre

I thought decoupling capacitors were optional “nice-to-have” filters that stubborn old electrical engineers put on schematics to look smart.

So I left them out to save board space.

The result? Every time the RP2350 microcontroller tried to switch a GPIO pin, the supply voltage dropped by 0.4V for a microsecond.

The MCU thought power had dropped, triggered a Brown-Out Reset (BOR), restarted, tried to switch the pin again, brownout, reset… a perpetual motion machine of instant crashing.

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🍻 The Final Verdict

After 4 bodge wires, 2 cut traces, and 3 hours of hot-air rework, the board finally booted up… only for me to realize I had made the mounting holes 2mm too small for standard M3 standoffs.

It now sits on my desk as a very expensive, very green coffee mug coaster.

    ┌───────────────────────────┐
    │  Ritesh's Rev 0.1 Board   │
    │  (Glorified Coaster)      │
    │                           │
    │      ┌─────────────┐      │
    │      │ ☕ COFFEE  │      │
    │      └─────────────┘      │
    └───────────────────────────┘

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Moral of the story: Always double check RX/TX, never skip decoupling caps, and always measure your screw holes twice. 🛠️