ThomasThe first working code is now on the GitHub develop branch.
The following features work:
- communication through PC.7 (LED display pin 3, segment DP)
- SWIM-programming-without-NRST through PD1 (LED display pin 4, segment C)
- 7-LED display with 1/8 MPX (hack for lower duty-cycle)
- controlling the LM2596 with PC.3 and PB.4
- Vin/Vout voltage measurement with ADC! and ADC@
When testing the code I noticed that the serial connection isn't always working reliably when I use the on-board LM317 power supply. I'll have to test if that's because of the very hacky Chinese-expert LED control without current limiting resistors, the "innovative" economization on the use of capacitors, or because of the rather poorly defined voltage threshold of the likewise Chinese CH340 USB-Serial chip I use for the very very hacky German single wire serial console in combination with all of the above.
I'll update this post as soon as I know the cause of the problem.
EDIT1: I tried an ARK3116 USB serial adapter: much better, very much better. Looking for that 10 years old mobile phone data cable in the basement is time well spent.
Lesson learned: if it works with a CH340 it works with about anything. If it doesn't work this doesn't mean much ;-)
EDIT2: the scope picture of my "multiplexed" serial interface doesn't look good: most likely I'm doing something wrong when changing the GPIO properties during LED MPX (which the CH340 isn't robust enough to handle). This will have to wait a bit, since for the next days I'll be on a business trip.
EDIT3: it's amazing what a small capacitor can do when it's no longer missing :-) I soldered a 100nF ceramics C between pin 2 of the LM317 and the adjacent ground. Now it works nicely.
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Shocking even something as "hackily-designed" as this can be purchased for so cheap... almost as shocking as the fact it'd be on the market in the first place. But, can't complain, what with its being recognizable parts instead of epoxy-blobs! Nice job fixing it up and making it even more useful.
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Thanks!
These guys spend a lot of time copying PCBs and BOMs. They even spend time figuring out how to lower the number of components, but almost always in the wrong places. It wouldn't take long to make this thing more reliable, more performant, more functional, or a combination of this without increasing the total production costs.
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I am a Chinese.All of these broads are made in China Shenzhen. Everyone in China can buy these on taobao(which is the largest online trading platform in China) .The people who designed the broad is not the professional electronic engineer.They are maybe just worker who worked for SMT factory. I think they will be very happy if someone can help them Improve product quality.
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Hi yongfeicao, thanks for your message! I've used taobao to identify some of those generic boards (most boards are also available abroad through AliExpress at sometimes significantly higher price).
It would be fun contributing to the improvement of these cheap boards, and it would be a win for everybody: better product for the end customer, a better margin for the manufacturer (at least initially), and more fun for the hobby electronics community.
The only problem: I wouldn't know how to contact any of the manufacturers, or their electronics design engineers.
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