Hi everyone!
This update was actually drafted in July, but in the rush of things I never hit “send.” So, here it is now — a belated but still important look into firmware, packaging, compliance testing, and a few surprises along the way. Since then, a lot has happened, so expect another update in the days to come.
Firmware Solid Enough to Ship
With release getting closer, I’ve been focused on putting the finishing touches on a stable first firmware version, the version that will be flashed on units before they head out into the world.
I rewrote the accelerometer-based inactivity and freefall detection to make it much more reliable. No more false positives when you wipe the tip a bit too aggressively in the metal sponge. I have to say, the LIS2DH accelerometer isn’t the most intuitive chip to configure but, once set up correctly, it’s surprisingly capable.
I also overhauled the power negotiation logic. The firmware now only requests what’s needed (yes, that should have been the case earlier), it handles edge cases more gracefully, and plays nicely with multiport chargers when new devices are plugged in. The new structure also makes it easy to add VINDPM support later, useful for the rare users powering the pen directly from a variable or unknown DC source.
One of the trickiest things has been working out a reliable way to store device info and user preferences. Until now, everything was stored in EEPROM in the MessagePack format, which is compact and flexible. But that strategy alone is vulnerable to corruption if power is lost mid-write. So, I’ve been designing a more robust approach to mitigate this.
I’ve also got heaps of small quality-of-life improvements in the pipeline. These will be rolled out post-release and I look forward to shaping them based on your feedback, as the firmware will be released on GitHub the day the units ship.
Packaging Format Change
From the start, I wanted the packaging to not be just a piece of disposable cardboard, but something you could keep and reuse to store and conveniently carry the product. That meant making it as compact as possible.
For compliance, the product must ship with a certain number of printed safety and usage instructions (even if the full manual is also provided online). However, when I explored printing a leaflet small enough to fit in the original packaging, I quickly learned that most printing companies either don’t support such small formats or only do so at a significantly higher cost. This left me with three options:
- Absorb the extra cost of a custom small-format print run, which I was reluctant to do especially since the upgraded cables had already pushed the budget — for good reason;
- Add an outer box to accommodate a standard-sized leaflet, which doesn’t really make sense environmentally;
- Slightly increase the size of the packaging to fit a standard A6 leaflet.
I chose the third option. At around 15x11x3 cm, the new packaging is wider, but also thinner. There are some potential benefits to this change for later down the road. For the upcoming year, distribution of the Solder Ninja Pen is handled by Crowd Supply and the very efficient logistics of their parent company, Mouser. But when that period ends, and I get to dive into the fun of selling and shipping units myself, as packages under 3 cm thick may qualify as regular mail in many countries, the size change opens up the door to potentially more affordable shipping for users who value money over time. Also, the upcoming Solder Ninja Tweezers should fit neatly in this same packaging format, and we love consistency.
Some More EMC Testing
As part of the compliance process, I’ve completed radiated and conducted emissions testing on the device. Radiated emissions refer to electromagnetic noise emitted through the air, while conducted emissions are unwanted signals that travel back through the power lines. Both can interfere with other devices if not properly controlled.
I had previously performed radiated measurements in a TEM cell, and just last week completed conducted emissions testing using my in-house setup. The results came out clean: all measured frequencies were below the applicable limits. These tests help ensure the product behaves properly in real-world environments.
Cable Trouble But Nothing Wasted
The initial batch of custom silicone USB Type-C cables came back with a mechanical defect: the sheath wasn’t properly anchored at either end, which can cause it to detach under repeated bending or if pulled.
This came as a surprise, as this manufacturer seems otherwise reliable. They didn’t offer a detailed explanation (my guess is that silicone-jacketed cables aren’t a very common request and some manufacturing specifics may have been overlooked). Mistakes happen and what matters is how they’re handled.
To their credit, they responded quickly and offered to remake the entire batch free of charge, covering everything except shipping. I also took the opportunity to switch to matte silicone, as the glossy finish on the first batch tended to attract dust. The replacement batch is expected to arrive this week.
Since they didn’t request the original batch back, I now have nearly 500 cables that are still suitable for static use. With the aim of reducing waste, I’m making them available at no markup, along with a clear usage disclaimer.
Protecting the Thermocouple Circuit
As mentioned in the previous update, I had become aware of a potential issue: if the tip is removed while heating is active, the voltage intended for the heater can momentarily short to the thermocouple signal, potentially over-stressing the analog front-end IC.
I’ve added a small protection circuit that clamps these transients, which will be included in the final PCB design. However, since I won’t have time to perform extensive endurance testing, I may still add a firmware warning as an extra precaution.
What’s Next?
As I hinted at in the intro, things have moved faster than the pace at which I’ve been able to publish updates. I’ve wrapped up the test jig (which honestly deserves an update of its own), received all the production parts, and started assembly. That means the last major hurdles are behind us. I’ll dive deeper into both the arrival of parts and the test bench in upcoming updates. The next big step will be shipping units to Mouser for final distribution. Once they receive them, it usually takes a short time for processing before backers begin receiving their pens. Based on the current timeline, deliveries to backers are expected around early November.
Regards,
Nicolas
