USB -> DB9 Converters

[WhoBeDaPlaya]

Need to drive a couple of dinosaur VFDs that only accept serial inputs. I did have them working from a native DB9 port on a decrepid machine, but would like to run them using something a little more modern.

Does anyone have experience with those little USB -> DB9 dongles? Any hassles?

The alternative would be to get an older laptop with serial port to do the job.

 

[imagoon]

Try here:

http://forums.anandtech.com/forumdisplay.php?f=4

 

[Jeff7]

In case I miss this thread if it gets moved...
A fair number of the cheap USB->232 converters use the Prolific chipset, which kind of works. Sometimes. When it feels like it. If it's not blue-screening the PC.


I've used stuff from B&B Electronics numerous times at work, though not specifically their USB->232 converter. Their 2-wire USB-485 converter is quite simple, and probably costs them <$10 in materials, but it also has the nice feature that it works consistently. They've also got lines of industrial-grade converters, complete with a few levels of optical isolation.


Edit: Bleh. Their UC232A uses the Prolific chipset too.


232USB9M - give this one a shot, unless you need the industrial features. This uses an FTDI chip, which is the same that is used in the 485 converter, and it's also used in an adapter board made by Digi/Maxstream. No problems with FTDI.

 

[WhoBeDaPlaya]

Thanks for the info Jeff. I've had many run-ins with that crappy chipset as well and hence why I'm hessitant to use a converter at all.

On the other hand, finding a cheap laptop with both USB 2.0 _and_ a native serial port is a little difficult.

 

[William Gaatjes]

When it comes to USB to RS232 or USB to SPI, I2C or 8 bit databus with r/w and strobe... FTDI seems to be the best choice. For as far as i know, FTDI was one of the first or even the first(I do not know for sure) and has the best driver support. FTDI did all the ground work. Works out of the box with windows or linux. And if drivers are still requested, FTDI has the drivers for you on the website.

This is a usb to rs232 converter from FTDI.
http://nl.farnell.com/ftdi/us232r-1.../dp/1329310?in_merch=true&MER=i-9b10-00001460

Should always work without hassle.
If you really need all the speed, the drivers allow even to customize some low level options such as buffer size polling speed and more.

FTDI website :
http://www.ftdichip.com/Products/Cables/USBRS232.htm

I have this version at home.
When using the D2xx drivers it can be used for a lot more then just as USB to RS232, or TTL level uart.

 

[WhoBeDaPlaya]

Ended up deciding to stick with a more modern laptop and use one of these guys :
http://www.amazon.com/36inch-Serial-...7128389&amp;sr=8-1

~$17 shipped 2nd day via Prime, FTDI chipset. Looks good to me

 

[wirednuts]

i use the cheapest usb to serial adapters they make. $3.50 shipped off ebay or dealextreme... and they use the prolific 2302 chipsets. the key is to get the right drivers. meaning do NOT use whats on prolific's website! horrible experiences! you end up finding drivers for some usb gps puck off globastats website and bam, they work great.

im sure if youre doing high traffic data stuff you would certainly want the ftdi stuff or similar quality, but if youre just trying to flash your router or something i havent had any problems with the cheap adapters, as long as you find proper drivers

 

[allenpan]

reason that the office site driver does not work, b/c those are are counterfit chip, as result of unable to funtion

http://www.eevblog.com/forum/produc...ge;PHPSESSID=14aaf494b95c5430d99cdccedf2c02e9

http://www.eevblog.com/forum/produc...ge;PHPSESSID=14aaf494b95c5430d99cdccedf2c02e9

 

[Modelworks]

The very first thing you should do when interfacing serial to usb is see what the device uses for voltages. It could be 5V, 3V , 15V depending on when it was made, then you can match it up with the proper USB interface. Using a 5V adapter for a 15V serial port will destroy the adapter, most usb laptop serial converters are 5V while the industry standard is composed of up to 15V positive and negative voltages. You really need a level shifter for ones like that. There are a few on the market , most use the sipex chip to handle the interfacing, it does the full voltage ranges.

The FTDI and prolific chipsets are for TTL connections (5V), not the industry standard 15V.

The one I use for all my work is made by JDI, it uses two chips inside, prolific for the usb and sipex for the voltage levels so it does cost more than other usb to serial cables, averages about $20. It is usually sold as the JDI GOLDX, part number is gxmu-1200. Check around ebay though I got 2 for $10 once.

 

[wirednuts]

reason that the office site driver does not work, b/c those are are counterfit chip, as result of unable to funtion

http://www.eevblog.com/forum/produc...ge;PHPSESSID=14aaf494b95c5430d99cdccedf2c02e9

http://www.eevblog.com/forum/produc...ge;PHPSESSID=14aaf494b95c5430d99cdccedf2c02e9

thank you! i should have guessed! i have researched that problem many times and never did i find any mention of fake chips. this clears everything up because ive noticed prolific driver problems for the serial chipset many times over multiple years now.

thanks again. even though it wont be possible to really know what youre getting until you buy it, its good to know that i should probably hang onto driver packages that work. that, or just buy name brand adapter$..... nope not going to happen

 

[William Gaatjes]

The very first thing you should do when interfacing serial to usb is see what the device uses for voltages. It could be 5V, 3V , 15V depending on when it was made, then you can match it up with the proper USB interface. Using a 5V adapter for a 15V serial port will destroy the adapter, most usb laptop serial converters are 5V while the industry standard is composed of up to 15V positive and negative voltages. You really need a level shifter for ones like that. There are a few on the market , most use the sipex chip to handle the interfacing, it does the full voltage ranges.

The FTDI and prolific chipsets are for TTL connections (5V), not the industry standard 15V.

The one I use for all my work is made by JDI, it uses two chips inside, prolific for the usb and sipex for the voltage levels so it does cost more than other usb to serial cables, averages about $20. It is usually sold as the JDI GOLDX, part number is gxmu-1200. Check around ebay though I got 2 for $10 once.

It is indeed true that FTDI converter pcb that i use, uses ttl levels : 5V or 3V3. I should have mentioned that. And that i use a separate level shift converter when interfacing to real RS232 voltage levels. Thank you for making that clear.

But the USB to serial RS232 cable has a normal levelshift converter added that can cope with standard RS232 levels of +/- 15V. For the people interested, these converters usually generate between +/- 5V and +/- 10V voltage levels at the RS232 pins of the DB9 connector. Usually a MAX232 or compatible converter from another manufacturer such as ST (former SGS Thomson).

For more information :
http://www.maxim-ic.com/datasheet/index.mvp/id/1798

.

 

[WhoBeDaPlaya]

Please get a MAX232. I need my RSU shares to increase in value

 

[sm625]

I've used many different kinds of USB to RS232 converters. The most reliable one I have found is: http://www.provantage.com/siig-ju-cb1s12-s3~7SIIU047.htm

The problems with the other cheaper ones were found through extensive testing, most likely any one will work for your application. I have not even encountered the problems myself, and I have run these for at least 100 hours. Right now I am using a TrendNet TU-S9. It is a $5 part and works fine for me.

 

[polarmystery]

Use FTDI. More expensive, but not a piece of shit like the other converters I've used. (the FTDI chip was the only converted which worked when I was programming an embedded device)

 

[Colt45]

I've not had much problem with any of them, lot of cheap prolific and arkmicro ones over the years.

Usually the problems involved aren't the USB<>ttl portion anyway, it's the ttl <>rs232 level shifter part. Some seem to cheap out on cap size, wiring, etc... so it only swings ±5V or so instead of the 10-15V neighbourhood. I Imagine they all use the same chip for this part though. max232 or some variation. So the actual USB side of things is immaterrial unless you're having driver issues, more or less. FTDI's prices are inflated to hell.

tl;dr
Unless you have a longass cable run or your device is designed poorly, a $2 chinese one will work fine, and no guarantees that a expensive one will perform better.

 

[Modelworks]

Please get a MAX232. I need my RSU shares to increase in value

Nope, not going to do it. I am getting a sipex chip

Seriously though, the Max chips are really good and the company is as well, they have always been very helpful anytime I had a problem and they are more than fair when it comes to samples.

 

[alkemyst]

I stick with Trendnet's products. I tried some cheap ebay ones and they usually have the same chipset, however; they fall apart and begin sending errors in daily use.

I am a network engineer so USB to Serial to Console cable is a daily need. Fortunately many new devices are going to a microUSB standard eliminating the console cable need.

The model number I have is TU-S9. These can be had for around $20 on amazon.