On Fri, 13 Jun 2008 03:53:32 -0400, CBFalconer <cbfalconer@yahoo.com> wrote:>CBFalconer wrote: >> Tom�s � h�ilidhe wrote: >> >> ... snip ... >> >>> Can anyone suggest a USB to RS232 adapter that does its job >>> perfectly 100% of the time under Microsoft Windows, i.e. it >>> trully behaves exactly just like any other serial port? >> >> Impossible. USB is not a serial port. > >I'm hearing some objections to my statement above. My point is >that USB is a shared system, and that it queues up traffic for >transmission at intervals. You can't use the adaptor to respond to >an input event in microseconds, as you can with the original port. >What you can do is asynchronous transmission and reception, which >is most people's objective. > >For example I believe that the original X-modem protocol will fail >miserably. That requires responding to a transmission with an ACK >(or NAK) within a very short time. Z-modem will probably work.I also very much doubt that you could use it with an external RS-232/485 converter with data direction control using the RTS line. Doing it properly is very hard even on any 14550 style UART, especially on any multitasking OS. Also implementing Modbus RTU with proper timing is going to be a challenge :-). Paul
Please suggest USB to RS232 adapter that works 100%
Started by ●June 12, 2008
Reply by ●June 13, 20082008-06-13
Reply by ●June 13, 20082008-06-13
Paul Keinanen wrote:> On Fri, 13 Jun 2008 03:53:32 -0400, CBFalconer <cbfalconer@yahoo.com> > wrote: > >> CBFalconer wrote: >>> Tom�s � h�ilidhe wrote: >>> >>> ... snip ... >>> >>>> Can anyone suggest a USB to RS232 adapter that does its job >>>> perfectly 100% of the time under Microsoft Windows, i.e. it >>>> trully behaves exactly just like any other serial port? >>> Impossible. USB is not a serial port. >> I'm hearing some objections to my statement above. My point is >> that USB is a shared system, and that it queues up traffic for >> transmission at intervals. You can't use the adaptor to respond to >> an input event in microseconds, as you can with the original port. >> What you can do is asynchronous transmission and reception, which >> is most people's objective. >> >> For example I believe that the original X-modem protocol will fail >> miserably. That requires responding to a transmission with an ACK >> (or NAK) within a very short time. Z-modem will probably work. > > I also very much doubt that you could use it with an external > RS-232/485 converter with data direction control using the RTS line. > Doing it properly is very hard even on any 14550 style UART, > especially on any multitasking OS. >You can do RTS control of RS-485 drivers, but you have even less accurate timing with USB than with a standard UART. An alternative is to use a feature of the FTDI chips - they can drive a RS-485 direction line directly whenever they are transmitting.> Also implementing Modbus RTU with proper timing is going to be a > challenge :-). > > Paul >
Reply by ●June 13, 20082008-06-13
In article <9bd63d75-3975-47d3-810a-361318b93f1f@ 34g2000hsf.googlegroups.com>, toe@lavabit.com says...> > I've purchased one already made by "Cypress Semiconductor" but it > doesn't work. The VID is 04b4 and the PID is 5500. > > Can anyone suggest a USB to RS232 adapter that does its job perfectly > 100% of the time under Microsoft Windows, i.e. it trully behaves > exactly just like any other serial port? >Keeping in mind the other posts in this thread AND that your mileage may vary; we use, and have never had a SINGLE problem with, the ATEN adapters. It may just be luck, or I just haven't tried the magic combo that blows it up, but those units have been rock solid performers for us. I don't know what chipset the units use and really don't care, because they work. They are a bit pricier than most of the crap out there. Just google or search on amazon: ATEN UC-232A and you will get plenty of info.
Reply by ●June 13, 20082008-06-13
I need an RS232 port for the following two reasons:
* For use with the GT ROM program for re-flashing firmware
* For programming PIC chips
The device that Don suggested looks very attractive but I'd just like
ask one more question:
My laptop has an "express card" slot. Would I be better off
getting an RS232 adapter that goes into the express card slot, or
should I go with the EasySync USB adapter?
Reply by ●June 13, 20082008-06-13
"Tom�s � h�ilidhe" <toe@lavabit.com> wrote in message news:9bd63d75-3975-47d3-810a-361318b93f1f@34g2000hsf.googlegroups.com...> > I've purchased one already made by "Cypress Semiconductor" but it > doesn't work. The VID is 04b4 and the PID is 5500. > > Can anyone suggest a USB to RS232 adapter that does its job perfectly > 100% of the time under Microsoft Windows, i.e. it trully behaves > exactly just like any other serial port?I have had the best results with Keyspan. The p/n on the one I use says USA-19HS. It is the most reliable that I have used. It has a TI USB3410 inside with a MAX3243 that I believe is just the RS232 level translator. Scott
Reply by ●June 13, 20082008-06-13
Tom�s � h�ilidhe wrote:> I need an RS232 port for the following two reasons: > * For use with the GT ROM program for re-flashing firmware > * For programming PIC chips > > The device that Don suggested looks very attractive but I'd just like > ask one more question: > My laptop has an "express card" slot. Would I be better off > getting an RS232 adapter that goes into the express card slot, or > should I go with the EasySync USB adapter?I just did a google, as I wasn't sure if they were readily available, but found plenty, pricey however. $90USD for this one: http://www.usbgear.com/computer_cable_details.cfm?sku=SS-AS1RS&cats=496&catid=1302%2C496%2C585%2C538%2C464%2C468 And I wouldn't know what sort of chip set these or others use. Some people may be aware. Now have a look at mine: http://www.dontronics-shop.com/easysync-premium-gold-usb-rs232-adapter-cable-10cm-cable.html Price includes world wide postage. It won't be the cheapest, but it works when most of the others fail. That is why I handle them. You can speak to the guys that designed the chipset, if you need in depth support. Re-read the guarantee of the ability to return the goods if it doesn't work for your application. Our loss on postage, all you pay is return postage. And re-read the customers feed back. I think there are 18 responses from Feb 2002, to Dec 2006. I simply stopped adding them. Applications that range from Garmin GPS's to Pfaff sewing machines. I doubt if anywhere else on the web, you will find a report such as this in the way of genuine feed back, on a USB to RS-232 converter. Please correct me if I am wrong. Cheers Don... -- Don McKenzie Site Map: http://www.dontronics.com/sitemap E-Mail Contact Page: http://www.dontronics.com/email Intelligent 2.83" AMOLED with touch screen for micros: http://www.dontronics-shop.com/product.php?productid=16699
Reply by ●June 13, 20082008-06-13
On 2008-06-13, Glenn M?ller-Holst <nomail@xx.dk> wrote:> CBFalconer wrote: >> Tom?s ? h?ilidhe wrote: >> ... snip ... >>> Can anyone suggest a USB to RS232 adapter that does its job >>> perfectly 100% of the time under Microsoft Windows, i.e. it >>> trully behaves exactly just like any other serial port? >> >> Impossible. USB is not a serial port.Actually it is if one is being pedanting, and this is Usenet so the pedantic flag is set by default. ;)> He properly means that he wants to have the RS232 tunnelled through USB > and showing itselves as a serial port in Windows.None of the USB->serial adapters (FTDI, Prolific, or any other) will behave "exactly just line any other serial port". The timings and latencies are going to be _way_ different. -- Grant Edwards grante Yow! Bo Derek ruined at my life! visi.com
Reply by ●June 13, 20082008-06-13
On 2008-06-13, Paul Keinanen <keinanen@sci.fi> wrote:> I also very much doubt that you could use it with an external > RS-232/485 converter with data direction control using the RTS > line.Unless the UART handles that itself (decent ones do).> Doing it properly is very hard even on any 14550 style UART, > especially on any multitasking OS. > > Also implementing Modbus RTU with proper timing is going to be a > challenge :-).Ah, I think you misspelled "impossible". -- Grant Edwards grante Yow! I would like to at urinate in an OVULAR, visi.com porcelain pool --
Reply by ●June 13, 20082008-06-13
In article <4852277C.2049C6BA@yahoo.com>, CBFalconer <cbfalconer@yahoo.com> writes:> CBFalconer wrote: >> >> Impossible. USB is not a serial port. > > I'm hearing some objections to my statement above. My point is > that USB is a shared system, and that it queues up traffic for > transmission at intervals. You can't use the adaptor to respond to > an input event in microseconds, as you can with the original port. > What you can do is asynchronous transmission and reception, which > is most people's objective. >I'll give you another (and probably more relevant for this newsgroup) example: the low cost serial port programmers that use the modem and hardware flow control signals to drive a microcontroller's onboard programming capabilities. See (for example) the serial port based AVR programmers. USB latency means that there's no way you are going to be able to run those over a USB to serial adapter, even if the adapter does a 100% accurate implementation of the modem and flow control signals. Simon. -- Simon Clubley, clubley@remove_me.eisner.decus.org-Earth.UFP Microsoft: Bringing you 1980's technology to a 21st century world
Reply by ●June 13, 20082008-06-13
In article <WeKdnav7neUXPs_VnZ2dnUVZ_uudnZ2d@posted.visi>, grante@visi.com says...> On 2008-06-13, Glenn M?ller-Holst <nomail@xx.dk> wrote: > > CBFalconer wrote: > >> Tom?s ? h?ilidhe wrote: > >> ... snip ... > >>> Can anyone suggest a USB to RS232 adapter that does its job > >>> perfectly 100% of the time under Microsoft Windows, i.e. it > >>> trully behaves exactly just like any other serial port? > >> > >> Impossible. USB is not a serial port. > > Actually it is if one is being pedanting, and this is Usenet so > the pedantic flag is set by default. ;)How true. 'U'niverial 'S'erial 'B'us Yep, definitely a serial port. :)> > > He properly means that he wants to have the RS232 tunnelled through USB > > and showing itselves as a serial port in Windows. > > None of the USB->serial adapters (FTDI, Prolific, or any other) > will behave "exactly just line any other serial port". The > timings and latencies are going to be _way_ different.The only BIG problem I have ever had was the fact that most of the adapters we tested had some strange glitches occurring on the outputs at very consistent intervals. Like 50KHz and ~100KHz on two I recall. I presume this was some artifact introduced by the chipset and the polling rate of the USB system/driver. In some instances these spikes were interpreted as start bits and things didn't go well after that. Jim
