Re: [vcf-midatlantic] portable terminal preferences
I'm curious what everyone else uses to connect to their various machines. Straw poll? Thoughts?
1) use a device with a REAL RS-232 UART. Not a USB/serial dongle. http://www.retrotechnology.com/memship/mship_usb.html Here's a somewhat busy note about using a FTDI-brand TTL-to-USB dongle, on a 8-bit microcomputer to a USB based modern computer. It references some other information too. But the problem I want to call out in general, is the "layers of character flow control" section of the document. The problem in brief, is that a USB serial dongle has its own buffers and hardware and software handshaking. It is a microcontroller after all. It's only vaguely controlled by the modern computer with the USB driver, which may or may not have user-means to operate. Most people use these dongles with old "terminal emulators" that think THEY have a buffer and some handshaking control of a UART. The USB driver arbitrates some of that, but not always well. It's all too busy, and generally means a slower sustained baud rate to avoid loss of characters. And for long runs of characters (like XMODEM) you get losses anyway. I think trying to run an 8-bit micro at 19.2K baud at length, is asking for trouble. But people get obsessed about high baud-rates. And certainly it's no fun, to transfer a file and find errors, even with XMODEM and other protocols. So - find a computer with a real, live, UART buried in it. They still exist. And in fact, that GPD MicroPC suggested, *has* (apparently) a RS-232 port. Too fancy for me, any 1990's laptop will do. Some of them still work well. Even some post 2000 laptops and desktops have serial ports. Use those, available from any industrial dumpster. Regards, Herb Johnson -- Herbert R. Johnson, New Jersey in the USA http://www.retrotechnology.com OR .net preserve, recover, restore 1970's computing email: hjohnson AT retrotechnology DOT com or try later herbjohnson AT comcast DOT net
following Sent from Yahoo Mail for iPhone On Sunday, January 3, 2021, 6:57 PM, Herb Johnson via vcf-midatlantic <vcf-midatlantic@lists.vcfed.org> wrote:
I'm curious what everyone else uses to connect to their various machines. Straw poll? Thoughts?
1) use a device with a REAL RS-232 UART. Not a USB/serial dongle. http://www.retrotechnology.com/memship/mship_usb.html Here's a somewhat busy note about using a FTDI-brand TTL-to-USB dongle, on a 8-bit microcomputer to a USB based modern computer. It references some other information too. But the problem I want to call out in general, is the "layers of character flow control" section of the document. The problem in brief, is that a USB serial dongle has its own buffers and hardware and software handshaking. It is a microcontroller after all. It's only vaguely controlled by the modern computer with the USB driver, which may or may not have user-means to operate. Most people use these dongles with old "terminal emulators" that think THEY have a buffer and some handshaking control of a UART. The USB driver arbitrates some of that, but not always well. It's all too busy, and generally means a slower sustained baud rate to avoid loss of characters. And for long runs of characters (like XMODEM) you get losses anyway. I think trying to run an 8-bit micro at 19.2K baud at length, is asking for trouble. But people get obsessed about high baud-rates. And certainly it's no fun, to transfer a file and find errors, even with XMODEM and other protocols. So - find a computer with a real, live, UART buried in it. They still exist. And in fact, that GPD MicroPC suggested, *has* (apparently) a RS-232 port. Too fancy for me, any 1990's laptop will do. Some of them still work well. Even some post 2000 laptops and desktops have serial ports. Use those, available from any industrial dumpster. Regards, Herb Johnson -- Herbert R. Johnson, New Jersey in the USA http://www.retrotechnology.com OR .net preserve, recover, restore 1970's computing email: hjohnson AT retrotechnology DOT com or try later herbjohnson AT comcast DOT net
Thanks for comments about USB dongles, RS-232 voltage/current levels and other war stories. I've added summary comments to my mentioned Web page as "watch out's". One can either use some vintage portable solutions, or some sets of modern devices built for purpose. An assisted laptop or portable handheld seems to be a simpler route than assembling keyboard, screen, controller and interface. A combination, as Bill Degnan suggested, is optimal. - regards, Herb -- Herbert R. Johnson, New Jersey in the USA http://www.retrotechnology.com OR .net preserve, recover, restore 1970's computing email: hjohnson AT retrotechnology DOT com or try later herbjohnson AT comcast DOT net
I could not find the content ... what is the url? Bill On Sat, Jan 9, 2021, 3:44 PM Herb Johnson via vcf-midatlantic < vcf-midatlantic@lists.vcfed.org> wrote:
Thanks for comments about USB dongles, RS-232 voltage/current levels and other war stories. I've added summary comments to my mentioned Web page as "watch out's". One can either use some vintage portable solutions, or some sets of modern devices built for purpose. An assisted laptop or portable handheld seems to be a simpler route than assembling keyboard, screen, controller and interface. A combination, as Bill Degnan suggested, is optimal. - regards, Herb
-- Herbert R. Johnson, New Jersey in the USA http://www.retrotechnology.com OR .net preserve, recover, restore 1970's computing email: hjohnson AT retrotechnology DOT com or try later herbjohnson AT comcast DOT net
I believe he's referring to the Membership Card Page: http://www.retrotechnology.com/memship/mship_usb.html On Sat, Jan 9, 2021 at 5:41 PM Bill Degnan via vcf-midatlantic < vcf-midatlantic@lists.vcfed.org> wrote:
I could not find the content ... what is the url? Bill
On Sat, Jan 9, 2021, 3:44 PM Herb Johnson via vcf-midatlantic < vcf-midatlantic@lists.vcfed.org> wrote:
Thanks for comments about USB dongles, RS-232 voltage/current levels and other war stories. I've added summary comments to my mentioned Web page as "watch out's". One can either use some vintage portable solutions, or some sets of modern devices built for purpose. An assisted laptop or portable handheld seems to be a simpler route than assembling keyboard, screen, controller and interface. A combination, as Bill Degnan suggested, is optimal. - regards, Herb
-- Herbert R. Johnson, New Jersey in the USA http://www.retrotechnology.com OR .net preserve, recover, restore 1970's computing email: hjohnson AT retrotechnology DOT com or try later herbjohnson AT comcast DOT net
As for having a dedicated terminal device… I have lusted after DEC’s handheld service terminal forever. It’s not super practical but it’s really cool. Same for something like a TRS-80 Model 100 or HP 200LX. Instead, if I don't want to carry around a VT-100/320/420, then I’ve got a pile of older laptops to choose from. Bringing us to USB-to-RS232 dongles, on which I’ll have to disagree, or at least say that your mileage may vary considerably. If you find one that works fine for you, it really opens up your options. The only problems I’ve ever had with USB-to-RS232 dongles has been dodgy drivers for the knock-off Prolific chips. Actual PL-23** dongles have always worked fine for me up to 115200 baud. (On many generations of Mac, using either ZTerm, minicom, or GNU screen, and the same on various Linuxes.) An increasing number of modern network & datacenter equipment even comes with USB “console” ports onboard. Just plug in a micro-USB cable to your laptop, and there’s a Prolific or FTDI on the other end ready to go. I can run these at 57600 to 115200 all day without trouble. These also are lovely in that if the USB cable fits, it’ll just work. No chasing down serial cable pinout mysteries. Now, interfacing to a vintage machine - it’s entirely possible the not-quite-in-spec voltage levels from a USB dongle could cause issues. I know I’ve seen this happen once, but it’s been too long to remember the specifics. If you’re doing some long-running data transfer with XMODEM and don’t have the luxury of any kind of error detection, well… I guess use what works best for you. OTOH, a generic $10 Prolific USB dongle worked just fine on my SYM-1 at its maximum speed (4800?). — Jameel Akari
On Jan 3, 2021, at 6:57 PM, Herb Johnson via vcf-midatlantic <vcf-midatlantic@lists.vcfed.org> wrote:
I'm curious what everyone else uses to connect to their various machines. Straw poll? Thoughts?
1) use a device with a REAL RS-232 UART. Not a USB/serial dongle.
http://www.retrotechnology.com/memship/mship_usb.html
Here's a somewhat busy note about using a FTDI-brand TTL-to-USB dongle, on a 8-bit microcomputer to a USB based modern computer. It references some other information too. But the problem I want to call out in general, is the "layers of character flow control" section of the document.
The problem in brief, is that a USB serial dongle has its own buffers and hardware and software handshaking. It is a microcontroller after all. It's only vaguely controlled by the modern computer with the USB driver, which may or may not have user-means to operate. Most people use these dongles with old "terminal emulators" that think THEY have a buffer and some handshaking control of a UART. The USB driver arbitrates some of that, but not always well.
It's all too busy, and generally means a slower sustained baud rate to avoid loss of characters. And for long runs of characters (like XMODEM) you get losses anyway. I think trying to run an 8-bit micro at 19.2K baud at length, is asking for trouble. But people get obsessed about high baud-rates. And certainly it's no fun, to transfer a file and find errors, even with XMODEM and other protocols.
So - find a computer with a real, live, UART buried in it. They still exist. And in fact, that GPD MicroPC suggested, *has* (apparently) a RS-232 port. Too fancy for me, any 1990's laptop will do. Some of them still work well. Even some post 2000 laptops and desktops have serial ports. Use those, available from any industrial dumpster.
Regards, Herb Johnson
-- Herbert R. Johnson, New Jersey in the USA http://www.retrotechnology.com OR .net preserve, recover, restore 1970's computing email: hjohnson AT retrotechnology DOT com or try later herbjohnson AT comcast DOT net
On 1/3/21 10:01 PM, Jameel Akari via vcf-midatlantic wrote:
Bringing us to USB-to-RS232 dongles, on which I’ll have to disagree, or at least say that your mileage may vary considerably. If you find one that works fine for you, it really opens up your options.
I have to agree with Herb on this one. I have friends who work on Railroad equipment that needs RS232C (supports +/- 25V). We've seen a lot of equipment that doesn't work well with USB adapters because they can't source the current. I do think the good PL-xxxx RS232C dongle work but the lesser ones fail miserable. If you drop a line driver in between it then works. On the issue of USB 1.1 (whose packet can handle 8 bytes) and serially connected devices: my friends and I have seen a problem with hand shaking skid (signal wait and sender skids to a stop). We've seen where changing the inter-character delays can help with this. Also the new line delays. That doesn't mean it can't work but you've got to know that there is a problem and were to look. I use a cheap ch340 USB TTl dongle and I have to cut a line at a time to paste to the device (115k). As far as a portable device, I use a chromebook as my serial terminal. -- Linux Home Automation Neil Cherry ncherry@linuxha.com http://www.linuxha.com/ Main site http://linuxha.blogspot.com/ My HA Blog Author of: Linux Smart Homes For Dummies
On Sun, Jan 3, 2021 at 10:43 PM Neil Cherry via vcf-midatlantic <vcf-midatlantic@lists.vcfed.org> wrote:
On 1/3/21 10:01 PM, Jameel Akari via vcf-midatlantic wrote:
Bringing us to USB-to-RS232 dongles, on which I’ll have to disagree, or at least say that your mileage may vary considerably. If you find one that works fine for you, it really opens up your options.
I have to agree with Herb on this one. I have friends who work on Railroad equipment that needs RS232C (supports +/- 25V). We've seen a lot of equipment that doesn't work well with USB adapters because they can't source the current. I do think the good PL-xxxx RS232C dongle work but the lesser ones fail miserable. If you drop a line driver in between it then works.
I agree as well... about 10 years ago, I had the occasion to try to bring a Bridgeport Series II CNC to life. Inside the Bridgeport was a real DEC LSI11 CPU board mixed in with all the Bridgeport boards. I was handed a sketchy hand-build Tyco-round-to-DE-9 cable and told "we can't figure out why the CNC won't talk". After I built my own cable, it still wouldn't talk to my laptop. I did some digging and I forget exactly what symptom pointed to the USB serial dongle we were all using with our laptops, but something did. I pulled out a desktop machine, plugged in the DE-9 cable I had made, fired up minicom and was able to push G-code to the CNC and move this massive CNC around. In the end, it was voltages... the mid-70s EIA circuit in the Bridgeport would not talk to any serial dongle, but worked fine with an ordinary "real" serial port (75188 drivers, IIRC) on a modern machine. Additional to this, I find myself sometimes needing to talk to very slow devices (below 300 bps, which is often the slowest divisor in the USB serial dongles). I do have gear at 45.45bps and 75bps and 110 bps. *Some* USB serial dongles have tools that let you overwrite entries in the factory divisor tables (600bps is frequently chosen because that speed has very little practical use with real devices). I have not done any such hacking, but I do know it's possible. What does work is real UARTs. Even the UARTs in AVR microcontrollers support all the old standards including 5-bit words and 2 stop bits. Sometimes there's divisor underflow for really slow devices, but you can clock the MCU at 4MHz and reach those slower speeds. If all you want to do is talk to stuff made since the 80s with 9600N1, most of this doesn't apply. If you want to talk to devices made in the 60s and 70s, you really want a "real" serial port. I've kind of wanted to take an old laptop (with a real DE-9 serial port and a UART) and replace the BIOS code with a dedicated firmware implementation of a VT100, but I've never wanted it badly enough to make one. I did gather the elements for one of Vince Briel's Propellor-based dumb terminals, but that only gets you the CPU. You still have to haul around (or borrow) an LCD at the destination site. -ethan
Whatever has been proven to work reliably is what use. If I want the convenience of a modern laptop and usb2serial adapter it's because I need to use the computer behind it too to send files or generate a log. I usually set up my super-reliable vt220 or something similar first, to make sure the settings and target computer are functioning. Then I swap in the laptop with usb2serial cable that is known to work with the model of laptop. Bill On Sun, Jan 3, 2021, 10:01 PM Jameel Akari via vcf-midatlantic < vcf-midatlantic@lists.vcfed.org> wrote:
As for having a dedicated terminal device… I have lusted after DEC’s handheld service terminal forever. It’s not super practical but it’s really cool. Same for something like a TRS-80 Model 100 or HP 200LX.
The only problems I’ve ever had with USB-to-RS232 dongles has been dodgy drivers for the knock-off Prolific chips. Actual PL-23** dongles have always worked fine for me up to 115200 baud. (On many generations of Mac, using either ZTerm, minicom, or GNU screen, and the same on various Linuxes.)
participants (7)
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Bill Degnan -
Ethan Dicks -
Herb Johnson -
Jameel Akari -
laurakid -
Neil Cherry -
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