which USB to TTL converter

There are various USB-TTL converters on the marketplace with different chips - CH340, PL2303, CP2102.

Which one is the better choice?

I don’t have the answer, but it probably should include which OS you are working with. What seems to be a non-issue with Windows can be an issue with Mac’s but not with Linux etc. (I too am curious about which is the better choice - at least for the Windows version of things (Win7/64)).

FT232R - No go, not if you’re buying a few modules online. Many of the modules online use counterfeit parts, and the latest drivers that FTDI has pushed out via windows update will not work with counterfeit chips (and a while ago, they put out a batch of drivers which actually bricked the fakes, so they didn’t detect anymore - this bricked a chip which I had built into a piece of equipment, assuming it was legit, and cost me about 4 hours of work). Since counterfeit chips and real ones can’t be identified when buying online, and since getting a refund out of a lot of these electronics vendors on ebay (at least the overseas ones) is futile, I recommend never buying an FT232R online.

I think one of the other ones (maybe the PL2303? ) has a problem with getting the drivers, because of a problem with counterfeit chips which led the manufacturer to stop supporting them.

I use the CH340G’s - they’re cheaper than dirt, so cheap they’re not worth counterfeiting, and they come in a SOIC-16 package that’s easy to work with, so you can solder on a flying lead to get the DTR pin so you can use the 99-cent-shipped ones to program Arduinii, or make your own board based on them without that much pain. I use a mix of my own-made CH340G adapters (on a custom PCB - I made one that breaks out all the pins) and 99-cent cheapo ones from china. However, apparently making them work on MacOS is tricky :-/

Very good information.

I see an adapter with the CH340 on eBay that has 6 pins -- they are GND, RXD, TXD, 3.3V, VCC, 5V http://i.ebayimg.com/images/g/Gd4AAOSwzgRW1Pap/s-l1600.jpg. Does that look right to you?

Just FYI, I bought this FT232RL , actually several and they work fine. Windows 10.

Whatever you get, if you want the Arduino auto-reset to work for uploading, get an adapter that brings out the DTR signal. For some reason, Chinese makers of the CG340G adapters have not really caught on to that. You would think since Chinese makers are producing Pro Minis by the thousands they would make a CH340G adapter that just plugs onto the end of a Pro Mini. I have seen posts on the forum where people discuss hacking theirs to bring out the DTR pin.

aarg: Just FYI, I bought this FT232RL , actually several and they work fine. Windows 10.

Good find. Ugh that I only have one USB to mini-USB cable.

dmjlambert: Whatever you get, if you want the Arduino auto-reset to work for uploading, get an adapter that brings out the DTR signal. For some reason, Chinese makers of the CG340G adapters have not really caught on to that. You would think since Chinese makers are producing Pro Minis by the thousands they would make a CH340G adapter that just plugs onto the end of a Pro Mini. I have seen posts on the forum where people discuss hacking theirs to bring out the DTR pin.

Excellent information. Most of the ones on eBay don't have the DTR pin. :roll_eyes:

ieee488: Excellent information. Most of the ones on eBay don't have the DTR pin. :roll_eyes:

All the ones that are for Arduino follow the Micro pinout so it can be connected straight across without wires. Of course, those all have DTR.

I use these, I buy 10-20 at a time. Mini USB http://www.tinyosshop.com/index.php?route=product/product&product_id=186&filter_name=ftdi%20 Micro USB http://www.tinyosshop.com/index.php?route=product/product&product_id=600

I have one of those TinySine adapters, it is very nice. It plugs directly into the Pro Mini. I have not used it with the latest Windows driver to test if it is counterfeit.

anyone of those will work fine. they are very simple devices. always see people whining about how evil the company who make the FT232R is, but it’s their right to update their driver to protect their work. if you got one of those, be smarter and get the older driver instead, and you will be fine. CH340G is a very capable chip, but again, there are people complaining about its low cost, no reset line, and driver problem, but it’s quite the opposite. A single Ch340G chip is slightly more expensive than the whole usb-ttl converter. how ridiculous is that? they don’t include the reset line because it doesn’t work on some boards. and most functions of the Ch340G are unused anyway. An USB to TTL converter really only needs Tx, Rx and gnd pin.

short answer, get an USBasp with ttl supported.

The CH340G chip has the DTR line, the modules often don't break it out though.

I don't know where you're buying your CH340G IC's, but you should find a new source. I paid 25 cents a pop for mine on aliexpress. afaik, the cheap serial adapters bottom out at about a buck.

arduinomagbit: they don't include the reset line because it doesn't work on some boards. and most functions of the Ch340G are unused anyway.

No, they don't support the DTR line because whoever designed them has no idea at all what he/ she is doing; simple as that, none other.

Some actually brought out the chip Reset line ("RST") instead (and the other useful lines on the side of the module), which was completely stupid, but vividly illustrates the point. They seem to have disappeared from eBay now, as apparently someone woke up to the horrible blunder, and redesigned it - but bizarrely simply swapped the Reset pin - which is 100% useless - for the DTR. :astonished: |500x499

aarg: All the ones that are for Arduino follow the Micro pinout so it can be connected straight across without wires. Of course, those all have DTR.

I needed to modify my search on eBay to get the right ones to show up.

Find the CH340 to be the best as well. But indeed, almost non have the DTR line broken out. Also the pin order is a bit weird and there is a 3V3 / 5V jumper om most but if you place the jumper there is no place to grab the voltage... So I just remove the header except the 3 pins for the jumper. Solder wires to the TX RX and GND locations, grab the middle pin of the voltage selection as a switchable Vcc (but you can't really load the 3v3) and solder a wire directly to the DTR pin. On the other end a header that is in the right order and it's superb. I even like a small cable between the module and the Arduino instead of the direct attachment. Bit more flexible.

septillion: Also the pin order is a bit weird and there is a 3V3 / 5V jumper on most but if you place the jumper there is no place to grab the voltage.

Well, the pin order is whatever it is - it is not by any means intended to replicate the FTDI.

The purpose of the "VCC" pin on these CH340 adapters is most curious. To what does it actually connect? There is no point in it going back to the CH340 as it already has the 5 V and 3 V pins. As far as I can determine looking at the adapters I have here (but I am reluctant to remove the transparent heatshrink), it merely connects to the pilot LED. Perhaps you connect the jumper to the terminal you do not need to use. :grinning: