Concerning the PETI Development Kit

Last Updated: 2022-01-16 15:00:00 -0600

Members of the #PETI channel on the Arcana Labs Discord Server may have already known this, but late last year I developed a plan to sell a small number of PETI Development Kits early. The plan was to have my prototype of the Rear Expansion Board milled, then either assemble or package them as kits together with the necessary components, TI Launchpad for MSP430FR5994, and other accessory boards. The idea was that if I sold the small number of extras I would have from that particular PCBWay order, it would help defray costs going into the last little streth of development.

The unanticipated flaw in this plan was a test escape in my validation of each of the circuits that went into the rear board, one that relies, as all good test escapes do, on arcana - admittedly rather minor arcana. You see, I created the hardware equivalent of a bug in the power management hardware, which limited the ability of the Development Kit as currently designed. The shortest explanation: in its current form, it can only use its own display when using alkaline batteries, and even then, it would require alkaline batteries above about 50% of their capacity. This is due to the way batteries work, the influence battery chemistry has on output voltage (the output voltage of NiCAD and NiMH rechargable batteries is almost a quarter volt lower than, say, Carbon Zinc), and, most importantly, the absence of input voltage regulation.

You see, if I had specified a boost converter or similar step-up regulator IC in the design, I could fairly trivially have boosted the output of any two AA batteries above what was needed for the LCD to operate. I might have paid a penalty in device longevity along the way (per set of batteries, of course), but at least it would have worked with any battery type.

I’m still looking at ways to solve this particular problem. I’ve identified a few ICs I find interesting enough to experiment with. The larger problem isn’t fixing this very-much-long-since-solved issue in electronics design; it’s the replacing of the boards. The REB has already gone through two revisions, at some expense. To order a third set of boards is out of the question, especially considering there is still some actual equipment that I don’t have for the lab which would have helped avoid cases like this. What’s more, at least for testing and development, this mostly isn’t a blocker for the development through version 1.0 of the firmware, with the exception of one feature surrounding power management.

So, in order to save my sanity, I’ve decided to do the following:

  • Offer the current remaining 4 Revision B development kits for sale. They haven’t been fully costed yet, but they’ll be available for direct purchase from me via Paypal Goods and Services. I’ll set up a post detailing things in full when I’m done.
  • Redesigning the Development Kit - and wider availability for Purchase - will happen very late in the PETI development cycle, and co-incide with the release of the Standalone version of the device and v 1.0.0 of the firmware. Probably, sometime in late 2022 or early 2023.
  • Proceed with the development of all outstanding firmware functions and the cleaning up of technical debt until such time as redesigning the back boards and ordering fresh ones is either feasible or required to progress.

The good news is, this in no way sets back PETI development and I should be able to press on ahead here without any real delay.

PETI is a major project intended to design and construct a virtual pet from Open Source Hardware and Software, and to encourage others to modify and tinker with similar projects. If you would like to support the development of this, or any of the other projects I’m working on for Arcana Labs, and you wanted to show your support financially, your best avenue is via my Github Sponsors account or by making a one-time donation to Arcana Labs via or through other avenues detailed here. Github Sponsors also get access to a special patrons-only section of the Arcana Labs Discord Server, where we talk about the ongoing super-secret project.