CH340C USB Serial Adapter 3-Wire Breadboard Test

[@Noname-hc4hc]

The chip has builtin 3v3 voltage regulator which is used internally if powered by 5v. Then V3 pin works as _output_ of that regulator. And If the pin is not used externally then attaching a small decoupling capacitor to it makes sense. To note: builtin regulator is not very powerful, maybe 20-30 milliamps of extra load, no more.

[@keithmaddox1469]

Nicely done. I have the same chip but haven't tried it out yet. I've used the FTDI chips in the past but these are nice and cheap and I've never had to install a driver as I've had to for the past for the FTDI. I think the drivers for both brands are delivered with the OS these days. These WCH USB chips are used all over the place now, but I don't recall ever seeing one with flow control ever being used. It'll be fun seeing you try these flow control lines out.

[@JohnsBasement]

I hope to see that flow control is tight enough for old UARTs with a 3 character FIFO. 😬

[@YoutubeBorkedMyOldHandle_why]

Decoupling capacitors seem to be poorly understood, (until recently even by me.) I just watched a video which gives a great explanation. According to this guy (and his scope), this is much more about inductance than capacitance. In a nutshell, he says you should pick the 'physically smallest' capacitor, and place it as close as possible to your IC pins. i.e. given the choice between an 0805, an 0402 (or heaven forbid ... a thru hole), you should pick the 0402, because smaller packages have less inductance, and are also easier to place close to the pins. As for the value, it doesn't make as much difference, but you may as well pick the highest 'practical' value in the small package size. e.g. a 1uF or 10uF will show a 'slight' improvement over a 100nF. Another huge consideration, is the rise and fall times on signals. Very sharp edges, will produce more noise due to inductive effects, which is particularly important with microcontroller pins. Ergo, while Sparkfun might be criticized for ignoring the datasheet, the more important issue is the size of the capacitors they used, and where they were placed on their board. Check out the youtube video by "Robert Feranec" called: "What Decoupling Capacitor Value To Use And Where To Place Them | Eric Bogatin"

[@PebblesChan]

You can forego having decoupling capacitors by using a well designed PCB PDN (Power Distribution Network). Robert’s a nice guy & has a good channel but take heed to the experts such as Dr Eric, Lee Ritchey, Dr Bruce Archambeault & Henry Ott for matters pertaining to signal integrity and EMC. Their books are excellent references. “Ground is a place where potatoes and carrots thrive!”. Rick Hartley & Suzy Webb are excellent practitioners of the associated PCB design.

[@ivolol]

DTR and RTS can often be used as part of an auto-reset during/after programming. e.g see sparkfun's esp32 thing schematic.

[@PebblesChan]

The simplest interconnect using many of the RS232 signals is to connect a DTE to a DCE device. e.g. Computer/Terminal to Modem. This configuration uses a straight through cable. The challenge is that with this configuration requires 2 modems and a line/line simulator to connect 2 computers/teminals together thus we have a plethora of different Null Modem cable configuations to omit the modems and line simulator. This is because ancillary signals such are often under software control with variances to their behaviour. Also be weary of the reaction time of systems to the handshake signals. Some are very slow to react and if not handled correctly will result in data overruns.

[@JohnsBasement]

Indeed! The lack of full duplex flow control in hardware is the cause of many a headache!!!

[@Otakunopodcast]

Heh, when I was looking for a chip to make a USB to RS232 adapter for my Z80 Retro board, I also looked at the CH340 chip, because it was actually available/in stock and is pretty cheap. But I decided against it, because the datasheet drove me nuts! Even though I'm pretty used to "Chinglish" from all the various badly translated manuals I've been exposed to over the years, this datasheet still threw me for a loop. I ended up going with the Silicon Labs CP2102N USB to UART chip, combined with the MAX3232 to convert the UART voltage levels to the RS232 levels that the Z80 Retro expects on the console port. A bit more costly than the CH340, and also slightly more difficult to solder (the CP2102N is a QFN and the MAX3232 is a SOIC with a pretty small lead pitch) but it was still very doable, even with my Neanderthal-level soldering skills, and the board I made works quite well, and both the CP2102N and MAX3232 have much more readable (dare I say "pleasant") datasheets.

[@microhobbyist]

I just used the MCP2221A on my Z80 retro homebrew, and it works flawlessly. You even have I²C on it.

[@JohnsBasement]

Sounds good! What bit rate do you normally run at? Any data overrun issues?

[@microhobbyist]

@@JohnsBasement I've been running it at 115200 without any issues for a while now. I'm going to double that rate when I receive my new board soon. However, I have a feeling I may be pushing the limits somewhat. But who knows. I'll keep you posted on the results.

[@jimtekkit]

I saw that the AgonLight2 is using a CH430T as the onboard USB to UART converter on that board. Olimex have the schematics on their website. It's a pretty cool SBC, definitely check it out if you haven't yet. They're running an eZ80 with 512K external SRAM and an ESP32 for I/O. I've got one on order.

[@JohnsBasement]

Be sure to read the datasheet on the EZ80 first. It is a cool chip. But depending on the sort of MMU your application needs, the Z180 should also be considered.

[@vanhetgoor]

I like RS-232 because it is robust and it is logical, furthermore it is vintage, computers used to exchange data in the old days.

[@JohnsBasement]

And it makes WAY more sense than exporting a graphic image of a bios config screen. Oh brother. 😒

[@andymouse]

Nice....cheers.

[@harveyellis6758]

Somewhat a waste of time watching someone jumping randomly around a datasheet and laughing.

[@JohnsBasement]

Eventually, youtube will add chapter markers so you can jump over what ever you get bored with.

[@YoutubeBorkedMyOldHandle_why]

What's even more boring, is spending 5 hours trying to debug a failed circuit, because you missed reading an important detail.

[@jimtekkit]

Don't put pressure on creators to deliver short videos. If a long video is required in order to cover all the important little details (and add some welcome personality), then so be it.

[@jackrubin]

That's not laughing - that's the cackle of hard-earned experience. It's a gift to be appreciated!

[@Andy-lf4di]

Try `dmesg -w` next time!