2/13/2021: I have successfully flashed APM32F103CB µcontroller being sold by RobotDyn. So it seems there is a reasonably priced replacement for the STM32F103C8, which cannot reasonably relied on to have the 131K flash needed to load OnStep. ver. 4.23. The RobotDyn "Black Pill" STM32F303cc can also be used but is too pricey to include in a $30 kit. It is also generally unavailable for purchase.
I don't see much point in offering the STM32 at $35 again when the fully featured MaxESP3 is available for $40. For the time being I will offer the STM32 with the APM32F103CB for $30 and without the processor for $25. When the current inventory of STM32 parts is exhausted I will have to reevaluate its future as a kit.
12/9/2020: Still working on the STM flashing issue. Drew has had luck using STM-Flash.exe (SourceForge) to upload the Arduino IDE compiled OnStep software to the CKS and APMF103C8 STM32 clones (AVR licensed). Trying to get a handle on using it.
11/24/2020: Done a bit of reorganizing here. In the right panel are quick links to the contents of the site. Hope they help you find what you're looking for. On the orders page is a listing of what's currently available. You can just copy and past the listing to your email with your selections indicated and save some time. In the How To page I've added a MaxESP3 assembly tutorial. I'm going through a few hundred emails to mine questions and answers for the FAQs, so there's nothing there at the moment.
MaxESP3 - $40 Fully featured controller at a great price, moderate skill level.
MiniPCB1 and 2 - $45 Powerful 600MHz µprocessor in compact packages. Easy to assemble and program with Teensyduino.
STM32 - $25.00 Everything to build the BluePill, except the BluePill.
$30 Same, but with a 131K flash STM32 or duplicate.
SHC ESP32 - $25 Features the 1.3" OLED display.
BHC - $10 Includes PCB, Momentary switches and RJ-12.
LV8729 or S109 step motor drivers $6 with Kit order.
PCBs, any of the PCBs for the kits may be ordered individually. $6 shipped in the U.S. $13 elsewhere.
Wemos D1 mini Pro and antenna substitution for D1 mini - $6.50.
HC-05 and BT adapter PCB for MiniPCB2 and STM32 - $9.
EQ-5 type mount motor brackets 2 @ $15. Provide 4mm of adjustment.
Aluminum enclosure for MaxESP3 -$14. Limited stock.
Aluminum enclosure for MiniPBC2 - $10. Limited stock.
ABS enclosure for the MiniPBC1 and BHC - $4
See menu above right for how to place an order.