In my previous post, A Brick Becomes a Diamond, I confessed my absolute dread of firmware updates. I outlined my tried-and-tested workspace mantra: "If it ain't broke, don't fix it!" Applying the version 3.0 update to my MicroPA50 amplifier was a rare exception because that unit was genuinely broken from the factory, constantly rebooting on oversensitive SWR spikes. The update transformed that brick of junk into a rock-solid, 40-watt diamond.
Flush with that victory, I returned to my bench feeling a bit too brave. I looked over at my Chinese clone uSDX+ "White Buttons" QRP transceiver. It was sitting there, doing perfectly fine. Did it have a few quirks? Sure. But it didn't need surgery.
Naturally, I broke my own rule anyway.
I decided I wanted to upgrade the code to add a few custom Morse code CQ messages. It sounded harmless. Fast forward several hours, and I had successfully trapped myself in a cascading nightmare of software locks, ghost buffers, a backward tuning knob, and a radio that was transmitting on completely incorrect frequencies.
If you have ever let workspace hubris get the best of you, here is the non-technical story of how I battled the uSDX+ firmware—and how a single line of code saved the day.
Hurdle 1: The Modern Computer vs. The Unsigned Driver
To send the new code to the radio, I used a standard USBasp V3 hardware programmer. Modern Windows 11 has incredibly strict security rules regarding unrecognized hardware, and the standard USBasp driver files are essentially digital antiques. Windows immediately blocked the programmer, refusing to acknowledge its existence.
- How it was navigated: I had to bypass the normal Windows infrastructure using a modern utility called Zadig. Zadig wraps the legacy file in a clean, digitally signed security capsule. Windows finally stopped panicking, and the flashing tool successfully established a link.
Hurdle 2: The Bluffing Error Message
The moment I hit the upload button, the software log screamed in bright red text: Error: cannot set sck period; please check for usbasp firmware update. It looked like a catastrophic failure.
- How it was navigated: This turned out to be a total bluff by the programmer clone. After locating the physical JP3 (Slow SCK) jumper on the USBasp board and bridging it to slow down the data speed, I re-ran the program. The red error message still appeared, but the data stream pushed right past it, completing a 100% byte-for-byte verified flash. Lesson learned: sometimes you just have to ignore the warning text.
Hurdle 3: The Persistent Memory Lock
I booted up the radio, eager to see my changes. My new callsign showed up flawlessly on screen (MY_CALLSIGN lives in the main Flash memory), but my old Morse code messages were still sitting there, completely untouched. Even worse, I realized the tuning was completely off. The radio now assumed it had a standard 27 MHz system clock tracking profile, but my specific "White Buttons" clone board houses a physical 26 MHz crystal.
Because the software math and the physical hardware crystal were out of sync, the internal VFO math completely broke down. The radio interface looked normal, but the actual tuned operating frequency was wildly incorrect on every band. I tried manually clearing the memory using command-line commands and hardware erase flags, but the radio completely ignored them—reverting to its old 27 MHz data blocks on every single reboot.
Hurdle 4: Walking Backwards and Overridden Variables
Before I could even tackle the clock, I ran into another headache: spinning the main tuning knob moved the frequency in the completely wrong direction. The rotary encoder was reversed. I opened up the massive .ino file and changed a configuration constant (like SWAP_ROTARY) to make the knob turn the right way.
Next, I tackled the frequency issue. I used the search bar, located every single active occurrence of 27000000 (the clock frequency constant), and meticulously updated them all to 26000000.
I compiled the code and flashed it again. The result? Total disappointment. The knob turned correctly, but the radio booted right back into its broken 27 MHz loop, the tuned frequency remained incorrect, and the old Morse code texts remained. Updating the base constants in the code text was completely useless. The uSDX core engine is built to protect the system profile. On boot, if it detects any pre-existing structural initialization signatures, it completely ignores the user’s code edits and restores the old 27 MHz data framework over your changes anyway.
The Ultimate Solution: Tactical Interception
The breakthrough happened when I dug deep into the code and found the exact line where the system menu binds the clock parameters to the chip:
case SIFXTAL: paramAction(action, si5351.fxtal, ...)
This proved that the uSDX engine forces its built-in memory blocks to load after the initial variables are parsed, completely undoing any user edits right at startup.
Instead of fighting the radio’s complex formatting layout loops, I decided to use a bit of tactical code interception. I went to the absolute last line of the radio's startup sequence (void setup()), right before the code exits to hand control over to the live tuning screen. I injected a single, unyielding line of absolute code:
si5351.fxtal = 26000000;By placing it at the absolute end, I let the radio finish its messy, stubborn startup loops first. Then, a millisecond before the radio actually woke up, my line stepped in, overrode the memory blocks, and forced the true 26 MHz clock frequency directly into the VFO processor.
The result was instantaneous. The radio booted up perfectly calibrated, and the VFO math was flawlessly restored—bringing the tuned operating frequencies back into perfect alignment across all bands.
The Virtue of Procrastination
When I updated my MicroPA50 amplifier, I learned that a little patience pays off, and that sometimes the next firmware release fixes the bugs you were planning to solder away.
But with the uSDX+ clone, I learned a different lesson: if you break your golden workbench rule and try to fix something that isn't broken, you better be ready to dig through thousands of lines of open-source math to find your way back out!
My portable field stack—the Elecraft KX-3, the MicroPA50, and the newly recalibrated uSDX+—is officially stable, accurate, and ready for action. But the next time I get the urge to touch a perfectly smooth piece of gear? I am leaving the USBasp in the drawer, turning off the soldering iron, and going out for a walk instead.
