Trying to make my own UNO clone, quick wiring question

[wilykat]

I wanted to use OSHPark's After Dark option to get black UNO board with copper traces under clear mask.  However the official schematic uses 8u2 or 16u2 in a very tiny package that aren't made for hand soldering.  I found a clone schematic that used FTL232 but I wanted to change that to CH340 instead.  Genuine FTL232 comes close to $5 a pop from reputible sources in single quantity, and I'd like to avoid clones.  FTDI bricked clones at one time in the past and I'd rather not risk getting my clone bricked by cheap clone.  CH340 are a cheap subtitute but uses smaller 16 pin package rather than FTDI's 28 pin package so I'd have to rewire the schematic for CH340.  Does anyone have a detail on which pin needs to be connected in detail?

[larryd]

Many here add an FTDI header then use an FTDI adapter (~$3-4) to communicated with the Arduino controller chip.

This way you only need one USB FTDI adapter for all your boards.

[WattsThat]

Schematic buried in here:

https://www.terraelectronica.ru/pdf/show?pdf_file=%2Fz%2FDatasheet%2FU%2FUNO_R3%28CH340G%29.pdf

[larryd]

Schematic buried in here:

https://www.terraelectronica.ru/pdf/show?pdf_file=%2Fz%2FDatasheet%2FU%2FUNO_R3%28CH340G%29.pdf

That's a Russian web site

[6v6gt]

If you want to use a CH340, look for an Arduino Nano clone schematic which uses these chips.
E.g. http://actrl.cz/blog/index.php/2016/arduino-nano-ch340-schematics-and-details/
has one, but look for others as well, and note the comments about tx and Rx pins if you use the actrl.cz design.
The chief differences between a Nano and Uno are in the power handling and the pin13 led.

[Paul__B]

Why would you want to replicate something so inconvenient a form factor as a UNO?

The FTDI "bricking" scam is a good indication not to use any FTDI chips, original or clone!  Solves the problem. 

[larryd]

"The FTDI "bricking" scam is a good indication not to use any FTDI chips, original or clone!  Solves the problem.  "

That has been rectified years ago. 

[wilykat]

UNO form factor may be "inconvenient" but a lot of shield is designed to fit UNO (and MEGA), I would need a Nano to UNO adapter to use the shield so might as well go straight to "inconvenient" UNO form factor. EDIT Nano can only have TQFP which would require desoldering to replace if I blow it. UNO can have 38 PDIP socket for quick chip swap. And onboard 5v regulator from external power source.

Pin 9, 10, 11, 12, 14, and 15 on CH340g seems to be unused in the 2 schematics above (one has 4 pin header connected to 9-12).  For external serial connection maybe? Most of the clones I've seen with CH340g chip don't have 4 pin header so I'll skip them.

I did notice 2 differences in the schematics.  The one 6v6gt posted has RX LED coming from TX pin on CH340 to RX pin on ATmega, and TX LED on RX pin to TX pin.  But other schematic has RX and TX LED reversed.  I don't think it really matters, both usually flashes too fast to tell which line has activity anyway.

Nonetheless I got the schematic and board finished.  I've sent the board to a cheap PCB fab for a prototype test to see if I missed anything.  If there's no error I will send it to OSHPark for the After Dark special: Black background with shiny copper trace under clear mask.  I've seen clones in many color (except all yellow or purple?) and black with clear mask would be a cool looking board.

[CrossRoads]

'328P is 28-pin DIP.

Do you have a source for CH340G chips? I am not aware of anyone selling them.

FT232 are good and solid, and do not fail with the regularity that folks seems to blow up the 16U2 on Uno/Mega boards. You don't hear of them going bad on Nano boards.

Yes, FT232 are $4.50 still (haven't seen that price come done in 9 years), price drops in bulk (10, 50, 100).
I won't design in any chip that I can't buy from a reputable US supplier, and CD340G doesn't fit that category.

As noted, the issue with the driver not working on fake chips was resolved years ago now.
I buy modules from tinyosshop.com and mouser.com and have not had issues.
I don't put bare FT232 chips on boards, we find the pins are too tight for consistent hand placement.

[6v6gt]

. . .
Do you have a source for CH340G chips? I am not aware of anyone selling them.
. . .

https://lcsc.com/search?q=ch340

I guess there are others too.

[wilykat]

Plenty of places to buy CH340G, and there aren't any issue with cloned CH340G being bricked like FDTI chips were: https://hackaday.com/2014/10/22/watch-that-windows-update-ftdi-drivers-are-killing-fake-chips/  Even though it's supposedly fixed, there's nothing to prevent FDTI from pushing a driver update that bricks counterfeit chips.  Genuine chip won't get bricked but $4.50 per chip means 2 less taco from Taco Bell for me.

CH340G is still cheaper, under $1 per single.  Yes, the driver needs to be manually installed on Macs and Windows but I haven't run into any issues.

'328P does come in both 28 pin DIP and 32 pin TQFP (and even smaller VFQFN).  Arduino UNO SMD officially has one: https://www.arduino.cc/en/Main/ArduinoBoardUnoSMD and the smaller '328P are commonly used in small boards  like Nano. But as I mentioned above, if I blow the chip I'd have to desolder it. There are socket for TQFP 32 but it's huge, much taller than the pin headers which would prevent shields from fitting, and the cheapest is around $15 for one thus a TQFP socket for UNO board isn't practical.

The 28 pin PDIP version of 328P can use a 10 cents socket for quick chip swap.

[CrossRoads]

I don't see a US distributor listed there, so lcsc.com is a no go for me.
I'm talking Digikey, Mouser, Avnet, Arrow, places like that.


Mouser has a limited qty of 340E, getting them sporadically from Sparkfun.com

https://www.mouser.com/ProductDetail/SparkFun/COM-16278?qs=vHuUswq2%252BsxPUC6%252Btb1UGQ%3D%3D
https://www.sparkfun.com/products/16278

CH340E vs cH340G - what's different?

[wilykat]

CH340E vs cH340G - what's different?

https://www.electronics-lab.com/ch340e-new-small-serial-usb-chip/

WCH, a Chinese integrated circuits manufacturer, has just released a new serial to USB chip called CH340E. Unlike other CH340 chips, it doesn't require an external crystal and also needs less PCB space and BOM.CH340 is a 3x3mm tiny chip comes in MSOP10 package and has 10 pins. Although it is smaller than other alternatives, it is a little more expensive than them. But considering other components and PCB size needed, the total cost of the BOM may be lower.According to Electrodragon, it needs only two external parts to build a full function circuit. They also tested it with up to 150,000 baud rate to flash an ESP8266 chip. Most features and technical specifications are the some for CH340 family including CH340E, so the same drivers will work with it.

Smaller, no external crystal.  However E's pin spacing is 0.5mm while G's pin spacing is 1.27mm so it's quite a bit narrower and harder to hand solder.  It's probably more for solder paste and reflow oven than hand soldering.

At a glance, it'd be almost easy to switch to CH340E:

RTS# and CTS# can be ignored when connecting on Arduino compatible board.  However there is no DTR# for reset (may require manual reset before uploading) and I have no idea what TNOW is.

[CrossRoads]

"E's pin spacing is 0.5mm"

That's Mega pin spacing.  Difficult.