Feliciano, you have become the “lucky” owner of another FNIRSI product, congratulations!
to be honest, I wouldn’t waste my time on this.
indman, I respect your opinion, but you should agree that it's not only FNIRSI, as most of "the chinese comrades" cut costs/corners wherever they can. So for most of us, unless we are lucky and get a very old stock, the chances for flashing the OSHW and enjoying all its benefits are more limited as time passes. At least, when rolling the dice, my luck got me an apparently genuine 44pin MCU.
So, I rather invest some time on this unit than putting it aside or thowing it away. But to convert this schematic to the original one it's not feasible, as the changes are too many. Therefore if @madires and you and other readers can please support this new mod, I will appreciate it, and I think it will be of benefit for other "lucky" owners too.
My thoughts on finalizing this miracle of Chinese thought:
1. Remove STC and forget about it!
2. Try to improve the circuit
As I don't want to cut/lay many traces: I haven't spent much time trying to understand the m-firmware code, I don't know whether the communication between PD1<->PD2 is needed (which could be acheived by a resistor). And about pulling PD1 low for reset or menu access, and PD2 high for triggering the boost converter, I don't know whether this can be achieved by another STC substitution circuit, and/or by connecting it differently, and/or by some tweaks on the code. In fact, by reading the power supply part of the similar schematic (which I'm adapting from an m328p TC1 clone), on my unit the press of the button is detected by a low on pin 42, answered with a high on pin 16 to trigger the boosters. Could it be to use the traditional auxiliary PCB, but connecting P1 to Q2c and P3 to Q3b (by an additional resistor) the way to go, ar at least part of it? As I said, I don't know the code, so I can't tell.
3. Check the assignment of the display contacts to the microcontroller, as they may also differ from the standard ones.
I will. In the meantime, I can tell the ISP is the standard one, and gets recognized by my USBasp as an m324pa.