usb to serial cable - Page 1
Forum section: electronics / general

author: Rerouter
author_rank: Super Contributor
timestamp: March 22, 2013, 02:03:51 pm
content: hello all, i'm looking for some recommendations on a usb to serial cable for old equipment, we have tried 1-2 cheaper models without much luck with our software, and would like to get some recommendations on some models that are known to work, 2 of the devices require all 8 pins to function as if a physically installed port,why usb over a card is that its for a laptop with no expansion slots, and only 2 usb ports, so for the moment we are stuck.

author: asbokid
author_rank: Regular Contributor
timestamp: March 22, 2013, 02:26:47 pm
content: The USB-RS232 bridge cables from China work fine. Those based on the Prolific PL2303 appear more reliable than the Winchiphead CH341. There is also the SiLabs CP2102 and the FTDI FT232 to choose from. Cables cost as little as 99p (AUD1.44). Worth having a few in stock, if they're a crucial component.cheers, a

author: lgbeno
author_rank: Frequent Contributor
timestamp: April 10, 2013, 03:13:41 am
content: Hands down, ftdi are the best and the drivers are included in windows.http://www.ftdichip.com/Products/Cables.htmYou get what you pay for with these cables always. I can't tell you how frustrating it is to get prolific based ones to work but sounds like you already did...

author: Bored@Work
author_rank: Super Contributor
timestamp: April 10, 2013, 05:21:29 am
content: Didn't you ask that question before?No such adapter can 100% replace a real RS-232 interface. Any device relying on some precise, e.g. bit banged timing will be in trouble, because USB buffers until either a data packet is full or some timer expired, messing up the timing between bytes.Regarding Prolific adapters, they work out of the box - on Linux. No questions asked, just plug and play. On Windows the driver is an incredible PoS to install. You need to wave a dead chicken and sacrify a virgin. (If you can't find a virgin the trick is to uninstall, yes uninstall, the driver software while the adapter is still plugged in. Then reboot with the adapter plugged in. Then use Windows "install from a list" to select a driver. The uninstall while plugged in leaves the driver on Windows, while it undoes some damage the Prolific installer did to Windows.)

author: notsob
author_rank: Frequent Contributor
timestamp: April 10, 2013, 05:40:15 am
content: If you want a general purpose 'lab' unit this has the lot, you can separate the boards if you only want the usb - 5v - 3v3 bit, it uses the silabs chipset and driverhttp://www.ebay.com/itm/CP2102-USB-TTL-RS232-Serial-Port-Converter-Transceiver-/230308271855?pt=US_Parallel_Serial_PS_2_Cables_Adapters&hash=item359f7156ef

author: codeboy2k
author_rank: Super Contributor
timestamp: April 10, 2013, 06:18:42 am
content: Quote from: Bored@Work on April 10, 2013, 05:21:29 amThat's about right, BAW is not exaggerating. I have a Chinese USB->Serial adapter, it's using the Prolific *clone* chip, which is apparently very common to see a clone, not a real Prolific chip. The Prolific drivers have devised a method to detect the clones chips and refuse to work with that chip. You have to uninstall what was automatically installed by Windows and try to find another driver that might work, and try again. Several timesI finally did get it to work and all is fine now, but it's not a simple plug and play on Windows, only because the Prolific driver does what it does with the clones.

author: casper.bang
author_rank: Frequent Contributor
timestamp: April 10, 2013, 06:53:49 am
content: I've been playing both with Prolific and FTDI adapters and my experience is that both are about equally well supported in most Linux kernels by default, also had no trouble on Windows but that may be because I'm using a genuine Prolific chip rather than a clone. The FTDI appears to have better signal output quality (whatever that means in practice), see somescope shots here.

author: peps1
author_rank: Regular Contributor
timestamp: April 10, 2013, 10:42:35 am
content: +1 for FTDI

author: Bored@Work
author_rank: Super Contributor
timestamp: April 10, 2013, 04:11:21 pm
content: The thing is in my collection of about ten Prolific cables there is not as single one that does work out of the box under Windows. Some of these cables should have genuine Prolific chips, they were bought from reputable brands.Because of this and some other observations I don't believe the Prolific claim that it is a clone issue. Prolific changed their story over time.Prolific Windows drivers were always shit. They used to claim their drivers were just samples, and one should get a real driver from a cable's manufacturer. Who of course were just pushing the original prolific drivers. Than Prolific managed to get their driver installation so badly broken that their installation didn't even run. This went on for something like two years, until they came finally around to "fix" the installation. And then they changed the story to this clone thing.As far as I could figure out the issue is they try to replace an existing Windows driver with a version they probably did find in the garbage bin. And this goes wrong. It is totally unnecessary because their drivers do work with the original Windows version. Maybe their developer's PC is broken, hacked, virus infected, and is missing that file or what. Their developer is probably the janitor's son needing some pocket money ...What happens when you uninstall the driver while the cable is still connected is that the uninstaller undoes the damage they did to Windows, while at the same time Windows makes shure the real driver files can't be deleted, because they are in use. You end up with only the needed files still on Windows, but not registered as drivers. If you do select them as driver after a reboot they magically start to work. And all those claims about their drivers having special clone detection features no longer make sense.And this is one of the many reasons why I prefer Linux over all this Windows shit.

author: lgbeno
author_rank: Frequent Contributor
timestamp: April 12, 2013, 05:10:56 pm
content: Quote from: peps1 on April 10, 2013, 10:42:35 am+1000 for ftdi seriously, I loath Prolific.

author: nctnico
author_rank: Super Contributor
timestamp: April 12, 2013, 11:36:25 pm
content: Quote from: lgbeno on April 10, 2013, 03:13:41 amI disagree. I'm having a lot of problems especially when switching from one program to another using the same port. Also switching the power supply on/off on a device connected to an FTDI chip causes the link to break. Silabs' CP2101 behave much better. The problem is that a lot of things seem to work fine until you kick it in the nuts.

author: G7PSK
author_rank: Super Contributor
timestamp: April 13, 2013, 05:08:28 pm
content: If you have a PCMCIA or PCMCIA mini or express slot one of these would be better.http://www.usconverters.com/index.php?main_page=product_info&products_id=251

author: gautamdamodar
author_rank: Contributor
timestamp: April 13, 2013, 05:23:59 pm
content: I have know experience with FTDI based converters but using a Prolific based one. Only RX/TX lines are working and was not able to interface a PIC serial programmer due to handshaking problems.

author: Hardcorefs
author_rank: Regular Contributor
timestamp: April 16, 2013, 12:21:02 pm
content: Stay away from the prolific RS232 products... they are WAY too much trouble.go grabFT232RL Break out board, there are 20 connections plus a 3 level voltage converter.covers absolutely EVERYTHING you would need RS232+ handshaking and user programable I/O.I buy them in lots of 10 and have not had a problem as regards to interfacing or drivers.

author: metalphreak
author_rank: Frequent Contributor
timestamp: April 17, 2013, 03:22:03 am
content: Get one with a genuine prolific chip and you won't have any issues.Getting one with a genuine chip IS the issue. You have to use drivers from 2007 or something silly to get the counterfeit ones to work in windows. I've never had any issues under linux.The SI Labs CP2102 based USB to TTL dongles I've used have always been much more reliable. They also break out pins for DTR DSR RTS CTS SPD SPD' DCD etc. You'll need one with an additional level converter if you're talking proper RS-232.http://www.ebay.com.au/itm/New-CP2102-USB-2-0-to-UART-TTL-6PIN-Connector-Module-Serial-Converter-/390568166974?pt=LH_DefaultDomain_0&hash=item5aefad463e&_uhb=1#ht_3264wt_1401At those prices, why bother with prolificThis might be suitable for RS232:http://www.ebay.com.au/itm/CP2102-USB-TTL-RS232-Serial-Port-Converter-Transceiver-/230308271855

author: jhalar
author_rank: Regular Contributor
timestamp: April 17, 2013, 07:28:34 am
content: I use a FTDI based USB<->RS232 converter from easysync.co.uk and found it to work with a lot of oldcomputer and network equipment so far. Bought mine in Australia through dontronics-shop.comhttp://www.easysync-ltd.com/product/527/es-u-1001-r100.htmlUsed to have lots of trouble with old network equipment serial ports using chinese made converters,the atten model UC-232 being the best of the lot.

author: Hardcorefs
author_rank: Regular Contributor
timestamp: April 17, 2013, 07:30:05 am
content: Yep... just wait until you are working on a project that requires an 'ARM' kernel......, 'Android'then you will see which chips are supported......

author: ptricks
author_rank: Frequent Contributor
timestamp: April 17, 2013, 11:46:34 am
content: Does the device that needs the serial port do anything out of spec like use some of the voltages on the pins for power ?If it does that makes it a lot harder because you need something that can source the -12V and 12V lines and not many usb to serial cables do that.

author: Rerouter
author_rank: Super Contributor
timestamp: April 18, 2013, 02:37:39 am
content: it was more the option of bit banging, which i'm happy to see is an option on FTDI based adaptors,as it turns out most of my problems came from windows xp using an api as opposed to direct port manipulation, however the above info means i can attempt to rewrite the old dos tool or try and find some emulating driver, (any thoughts?)thank you all