Where to buy cheap USB to Serial Adapter

BillBWann

Member
Can anyone tell me where I can buy a cheap USB to Serial Adapter. I bought some some years ago and they worked well but a couple of them have failed recently and I'm down to my last one.

I tried following the advice from SAborn in #12 of this thread and placed a couple of orders but they have both turned out not to support the break signal.

Hopefully someone has bought one recently that works and they deliver to Australia.

Thanks
 

inglewoodpete

Senior Member
I have used a variety of programming leads. I don't know why you are asking for advice on cheap USB to Serial adapter leads but maybe they fail more often, making them a lot more expensive! What fails? Is it the wiring fails due to yanking the ends too much? Or does the chip fail due to overvoltage damage?

I have a variety of leads from reputable suppliers, including Altronics, Jaycar and Rev-Ed. None have failed in over 10 years of regular use. In my opinion, the best one is the AXE027 (FTDI) from Rev-Ed - its output is at TTL levels.
 

techElder

Well-known member
Bill, since you mention the "break signal", we're assuming you are looking for an adapter to program PICAXEs. I've just always used the AXE027 for my programming interface.
 

Goeytex

Senior Member
The primary specification seems to be "cheap". So source from places like Ebay or AliExpress.

Your Options are generally:

FTDI, PL2303, CP2102 or CH340 based Converters.

FTDI: A geniune FTDI based adapter is top of the line. Howeverv, any FTDI based adapter that costs less than about $10.00 US is most likely a Fake/Counterfeit. Most on Ebay are fakes. This does not necessarily mean they will not work. But by purchasing a known fake you are supporting the theft of intellectual property. This applies to all fake/ counterfeit devices. The fake/knockoffs may or may not support break signaling and may or may not be programmable to invert the data lines as required for Picaxe programming.

Prolific PL2303: Genuine PL2303 based adapters work fine. Some PL2303 based adapters are fakes some are not. May or may not work. Take your chances. For Picaxe programming, I/0 lines need to be inverted unless it has a MAX 232 type chip on board. I have seem more problems on this forum related to PL2302 than any other type, probably because they were fakes.

CP2102
: Genuine CP2102 based Adapters work great. But again many many are fake/counterfeits but most work ok. I/O pins need to be inverted for Picaxe Programming.

CH340/341: Made in China. Unlikely to be counterfeit because these are cheap (inexpensive) to start with. Support break signaling. Seem to work fine. I/O lines need inversion unless MAX232 chip on board. May have to search around for correct driver.

If you can get past the "cheap" specification then get an AXE027 from Rev-Ed.


Good Luck.
 

AllyCat

Senior Member
Hi Bill,

I tried following the advice from SAborn in #12 of this thread and placed a couple of orders but they have both turned out not to support the break signal.
Were the adapters you got described as using the CH340 chip? Is it definitely only the break signal that's not working?

AFAIK, the CH340 chip does support break signalling and drivers are available even for Win10 64 bit. Are you sure the correct driver is installed? Links to the adapters that don't work would be useful, if only so that at least we can avoid recommending them again.

Stan Swan (manuka) is in your part of the world (NZ) and some time ago prepared a "help" guide to identify the good "blue" adapters from the "fakes". But I believe he bought them from China with success (as I have); perhaps we were just lucky.

Particularly with the Chinese New Year now, it's difficult to decide whether to wait for a delivery from China. But if not in a particular hurry, I still would choose one of the more established Chinese sellers on ebay, provided that the description includes "CH340" (or 341) and not "TTL".

Cheers, Alan.
 

BESQUEUT

Senior Member
The primary specification seems to be "cheap". So source from places like Ebay or AliExpress.

Your Options are generally:

FTDI, PL2303, CP2102 or CH340 based Converters.

FTDI: A geniune FTDI based adapter is top of the line. Howeverv, any FTDI based adapter that costs less than about $10.00 US is most likely a Fake/Counterfeit. Most on Ebay are fakes. This does not necessarily mean they will not work. But by purchasing a known fake you are supporting the theft of intellectual property. This applies to all fake/ counterfeit devices. The fake/knockoffs may or may not support break signaling and may or may not be programmable to invert the data lines as required for Picaxe programming.

Prolific PL2303: Genuine PL2303 based adapters work fine. Some PL2303 based adapters are fakes some are not. May or may not work. Take your chances. For Picaxe programming, I/0 lines need to be inverted unless it has a MAX 232 type chip on board. I have seem more problems on this forum related to PL2302 than any other type, probably because they were fakes.

CP2102
: Genuine CP2102 based Adapters work great. But again many many are fake/counterfeits but most work ok. I/O pins need to be inverted for Picaxe Programming.

CH340/341: Made in China. Unlikely to be counterfeit because these are cheap (inexpensive) to start with. Support break signaling. Seem to work fine. I/O lines need inversion unless MAX232 chip on board. May have to search around for correct driver.

If you can get past the "cheap" specification then get an AXE027 from Rev-Ed.


Good Luck.
+ :
Some fake chips work with W 7
but when I try theses with a new computer, W10 says "this is a fake" and refuse loading driver !
 

BillBWann

Member
About 6 months ago, I bought from these two Chinese sellers

http://www.ebay.com.au/itm/400780981792?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT

and

http://www.ebay.com.au/itm/400789845760?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT

When they didn’t work and following SAborn’s advice I placed orders with

http://www.ebay.com.au/itm/262723866610?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT

and

http://www.ebay.com.au/itm/231835202545?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT

Only this last mentioned order has arrived so far but it also doesn’t appear to work. They all work fine for normal serial transfer but of course I want to also be able to program with them.

They all show up in Device Manager as “USB SERIAL CH340 (COM6)” just like the one original cable that does work so I assume that it’s not a driver problem. Contrary to what Goeytex suggests, none of the “blue” cables that I’ve bought have required inversion. As I say, they all work fine for serial transfer. They just don’t program.

Just for the record inglewoodpete, I’m not that destructive with them. I bought 3 initially many years ago. One stopped working a few years back which may have been my fault because I was having hardware problems at the time. I also seem to have misplaced one of my original cables which leaves me with just one working cable and I feel a bit vulnerable so I’d like to have a spare at least.

I will get an AXE027 if I need to but when postage is included, it’s an order of magnitude or more expensive and I’ll have to make up an adapter cable because I use 3 pins and not the stereo plug.
 

erco

Senior Member
Contrary to what Goeytex suggests, none of the “blue” cables that I’ve bought have required inversion. As I say, they all work fine for serial transfer. They just don’t program.
Did you try inverting them to see if they will program? A ten-minute breadboard experiment might answer some questions. Does the Picaxe editor recognize the chip? Which OS?
 

Goeytex

Senior Member
They all show up in Device Manager as “USB SERIAL CH340 (COM6)” just like the one original cable that does work so I assume that it’s not a driver problem. Contrary to what Goeytex suggests, none of the “blue” cables that I’ve bought have required inversion.
I said that inversion was needed "unless there was a MAX232 on board" === >>> The USB to RS232 cables have a Max232 type chip on the adapter board inside the cable.

I have never used CH340 based "Adapter Cables" as I do not like using RS232 voltage levels with a Picaxe. I do use and have a few CH340 USB/TTL "Adapters" where the signals need to be inverted for Picaxe programming.
 

inglewoodpete

Senior Member
I will get an AXE027 if I need to but when postage is included, it’s an order of magnitude or more expensive and I’ll have to make up an adapter cable because I use 3 pins and not the stereo plug.
I'm not sure what you mean by "order of magnitude more expensive" with postage, unless you can buy a reliable cable for A$4 elsewhere. Wiltronics have the AXE027 for A$27.95 plus postage. When faced with a situation like this, I check my parts drawers and upcoming projects and order more stock to diminish the significance of the postage overhead.
 

manuka

Senior Member
Without trying to start a micro shootout,it may be timely to point out that PICAXE family programming hardware has remained unchanged in - gasp- 15+ years.

Wireless has since ENORMOUSLY blossomed of course,with even Espressif's cheap but esteemed WiFi ESP8266 modules now able to handle an "ESP8266 BASIC Interpreter". No wired programming links are required,as a web browser (PC.smartphone or tablet) serves to address the module via it's IP.

Aside from the versatility (& given that device users traditionally hate wires), it's perhaps worth pondering the IoT implications of this wireless approach... Stan.
 

BillBWann

Member
Inglewoodpete. Yes, the ones I bought originally that work and the ones I’ve bought recently that don’t work have all been under $2 each including postage – which is admittedly a ridiculously low price to be paying. Thanks for the advice on Wiltronics. For some reason, I’d forgotten about them as an option and had only considered the UK option.

Stan. Thanks for the advice. I emailed to the site you mentioned but so far haven’t got a reply. They look to me like they may only be interested in large orders like you could make.

Goeytex. All the blue cables that I’ve bought (both the ones that work and the ones that don’t) are all negative polarity TTL voltages – ie they idle at zero and rise to 5 volts for a high bit. I’m sure that the only difference between the ones that work and the ones that don’t is the lack of a break signal. Thanks for the advice on the other converters. I do have some cheap Chinese converters with the opposite polarity and I’ll check them to see if they support the break signal. If they do, then I can add the inverters.

AllyCat. Do you agree with my conclusion that if both the cable that works and the ones that don’t all show up in Device Manager as USB-SERIAL CH340, then it’s not a driver problem that causing the new cables not to work?

I’m still looking for an ebay site that sells “blue” cables that are known to work so if anyone knows one, please let us all know.

Thanks
 

manuka

Senior Member
BillBWann: It's at least 3 years since I bulk purchased & in that time suppliers & internal hardware indeed may have significantly changed. I also bought a swag from Kiwi Trademe outlet "JerryScience", & this reputable firm seems to still be active - see => http://www.trademe.co.nz/computers/cables-adaptors/usb/auction-1249424292.htm

If you really want a few of my spare "bluies" then maybe I could send them TransTasman? In fact my youngest son will be in Melbourne (Monash) from mid Feb., & may even be persuaded to bring a few over ? Stan.
 

MFB

Senior Member
Without trying to start a micro shootout,it may be timely to point out that PICAXE family programming hardware has remained unchanged in - gasp- 15+ years.

Wireless has since ENORMOUSLY blossomed of course,with even Espressif's cheap but esteemed WiFi ESP8266 modules now able to handle an "ESP8266 BASIC Interpreter". No wired programming links are required,as a web browser (PC.smartphone or tablet) serves to address the module via it's IP.

Aside from the versatility (& given that device users traditionally hate wires), it's perhaps worth pondering the IoT implications of this wireless approach... Stan.
Stan

Thanks for the heads-up regarding ESP8266 BASIC. Certainly looks very useful for WiFi based applications, once the initial programming and configuration tasks have been mastered.

Both the PICAXE and Arduino development environments have changed little over the past years, but then if it isn’t broke why fix it?
 

BESQUEUT

Senior Member
Without trying to start a micro shootout,it may be timely to point out that PICAXE family programming hardware has remained unchanged in - gasp- 15+ years.

Wireless has since ENORMOUSLY blossomed of course,with even Espressif's cheap but esteemed WiFi ESP8266 modules now able to handle an "ESP8266 BASIC Interpreter". No wired programming links are required,as a web browser (PC.smartphone or tablet) serves to address the module via it's IP.

Aside from the versatility (& given that device users traditionally hate wires), it's perhaps worth pondering the IoT implications of this wireless approach... Stan.
+1...............................
 

marks

Senior Member
Hi BillBWann,
I guess today we are spoilt by choices, nearly all new devices are TTL serial.

What many dont realise is once we connect a project with a USB device,
the negative supply rail is now connected to the mains earth. not always desireable.

The ch340g is one of the later products
supports break signalling
drivers load by themselves for w10 and w7 when connected to the internet.

currently playing with a 401 20m2 shield ( WHEN I GET A CHANCE)
the small add on board is used for optoisolation and converts TTL serial to Normal serial for programming.
Remove and move the shield jumpers to the right you can also use the axe027 through the socket as normal.

The ch340G is less than $2 delivered lol.
http://www.ebay.com/itm/CH340G-RS232-Upgrade-to-USB-TTL-Auto-Converter-Adapter-STC-Brush-Module-Golden-/201656306805?hash=item2ef3a70c75:g:AWYAAOSwxg5XxGqM
I must get another to try this, the G version can also be inverted (for Normal serial) just by making pin 15 high
pin 16 is Vcc so its just a matter of shorting these pins switch it on and off and i suspect
the tx and rx should then be lit .
 

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erco

Senior Member
I must get another to try this, the G version can also be inverted (for Normal serial) just by making pin 15 high
pin 16 is Vcc so its just a matter of shorting these pins switch it on and off and i suspect
the tx and rx should then be lit .
That's awesome news, must try that when I get a minute. If it works, you just saved a lot of inverter ICs. 74HC14 lives matter!
 

AllyCat

Senior Member
Hi Bill,

AllyCat. Do you agree with my conclusion that if both the cable that works and the ones that don’t all show up in Device Manager as USB-SERIAL CH340, then it’s not a driver problem that causing the new cables not to work?
Not necessarily (but I'm no expert on drivers). It was the "updated" drivers from FTDI that caused what it considered to be "fake" devices to no longer work.

Like you (and stan) it's some years since I bought any of the "blue" adapters, but I did fnd that they stll work on Win10-64 bit, even though a lot of the sellers say that they don't (probably to be safe rather than sorry). What I'm reasonably confident about is that any adapter sold with a sub-D 9 pin connector will be the correct signal polarity for PICaxe, however may well use only TTL levels, and there is no guarantee that it will support break signalling.

Until now, I/we were reasonably confident that any adapter using the CH340 chip would support break signalling. What may have happened is that there is now a "new" CH340 chip on the market which no longer supports break signalling. Maybe another manufacturer is making "fake" chips, or CH340 has become a "generic" chip, but somebody has made a mistake (in the break signalling functionality). Generic semiconductor chips are very common (probably started with 74 series TTL and 741 opamps, etc) and some product manufacturers will use only generics (to ensure second source availability).

Some of the adapters I bought that worked well, didn't even meet all of stan's criteria (e.g, they had blue thumbscrews and COB) but the latest "blue" adapters that you linked do appear to be a slightly darker blue. The "Gold" adapters described by marks now apppear to be the best option, but maybe not quite as rugged as ones with a 9-pin sub D. I did order one a few months ago, but didn't get around to fully testing it; I think maybe I had a problem finding a driver for XP, but must look again.

Cheers, Alan.
 

SAborn

Senior Member
There is a new CH340G chip on the market and all adapters i have tested with this chip dont work with picaxe, not because they dont support the break signal, but due to the signal data being inverted.

I am waiting on some RS232 boards to test out as add on's to correct the data inversion, as the RS232 boards are around Au$1.00 or less than it might prove to be a easy/cheap solution to convert any adapter.
Will report back once i get to test the add on RS232 boards out.
 

BillBWann

Member
Marks. I’ve ordered a couple of your suggested CH340G’s. They sound like they are just what I need. The connection to ground shouldn’t be a problem for me as I use a laptop but good information to know.

SAborn. I’m not sure what you are saying. Are you disagreeing with what marks said in #19? He seems to be saying that the data can be easily inverted (by shorting out pins 15 & 16) so I don’t see the need for the RS232 inversion.

Manuka. Thanks for your generous offer to persuade your son to bring over some cables. Even though we do go to Melbourne from time to time, I won’t ask you to inconvenience him at this stage as the solution offered by marks looks promising. Your offer is another example of your incredible generosity to this forum over so many years. Like so many others, I’m ever grateful for your introductory articles in Silicon Chip way back in 2003 which brought me to this forum and the many insights you’ve given us ever since.
 

erco

Senior Member
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SAborn

Senior Member
BillBWann ,

Yes i do disagree with Marks, I too got excited when i read the data sheet thinking the same as Marks, but got disappointed when i tested the board, then read the data sheet more carefully and found ... this...

Auxiliary pins: IR#, R232, CKO and ACT#. (Note: only R232 is present on CH340G) When
R232 signal is asserted the RXD signal is inverted. R232 is latched during Power-On Reset.
Its not the RXD line causing the problem its the TXD line that has the wrong idle level, if you use the Led test in PE the output for the TXD line of the CH340G chip is backwards why i suggest using an inverter of some sort, the board Marks suggests along with a RS232 board like Erco has posted a link to should solve the problem.
As i stated this is yet untested until my RS232 boards arrive, although i see no reason why the boards wont work as an inverter.
For the sake of a few minutes on ebay and the cost of $1.00 i suggest ordering a RS232 board for backup plan B.
 

marks

Senior Member
Hi BillBWann,
yes it seems ,I misinterpreted what the rs enable pin does
I decided to try and have a go at modify or bricking my board lol.
it appears as also SAborn has discovered only the rx is inverted.
And the TX is still required to be inverted as before
one solution is to add a BS250 transistor .I have just tested this and seems to work quite well.
I might try later to squeeze this into a stereo plug just to seen if it can be easily done.

and yess before someone tells on me I drew the 10k on the wrong side also ,so the example becomes a shield 401 now
 

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BillBWann

Member
Well, it’s not quite as simple as first thought but there are 3 alternatives that look like they’ll work or I could just simply use a hex inverter.

Thanks everyone for your contribution and if you do happen to come upon a cheap source of those “blue” cables that really work, do let us all know.
 
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