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Input Devices IT

Will the Serial Console Ever Die? 460

simpz writes "Will the serial port as a console connection ever be displaced — especially for devices such as switches, routers, SAN boxes, etc.? In one sense it's a simple connection. But it is the only current port that, in order to use, you need to know about wiring / baud rates / parity, etc. It has non-standard pinouts. And it is becoming too slow to upload firmware to dead devices, as the firmware updates get larger. Also, the serial port is rapidly disappearing from new laptops — which is where you often really need it, in data centers. Centronics, PS/2, and current loop are mostly defunct. Is there any sign on the horizon of a USB console connection?"
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Will the Serial Console Ever Die?

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  • I use one just fine with an old WACOM 12" tablet under linux, so while the port may be dead, we can still use serial software and hardware. There's no reason you can't use two $15 converters plus a null modem to run that old DOS-based serial telecom program (ah, telix ... thanks for the memories).
    • by Anonymous Coward on Saturday February 27, 2010 @10:53PM (#31301908)

      Also there are single chip rs232 to USB solutions available for a few dollars. They are used in lots of things these days. They are great for when the device your making only needs a simple serial port connection to a pc or other device. Arduino uses one on their boards. I cant really think of any other examples at the moment. But I dont see serial console dying anytime soon, its still really useful to have around.

    • by transporter_ii ( 986545 ) on Saturday February 27, 2010 @10:57PM (#31301936) Homepage

      I would like to point out that, while converters work just fine for almost everything, they do not work for everything. I've personally ran into equipment that would not read with a serial to USB converter. I've worked a little in SCADA, and you just about had to special order a laptop with a real serial port on it, or you just couldn't read all the equipment in the field.

      But if you know what you are wanting to use with a converter works, then they usually work just fine.

      • It depends on the serial-to-usb converter chip used. Some don't do a good job of replicating all the characteristics of the port. Best advice is try different types until you find one that works. The newer ones do a good job - the older ones were really hit-and-miss (mostly miss) affairs.
      • Re: (Score:3, Interesting)

        by Zerth ( 26112 )

        Yarg, I've got some industrial machinery that uses serial and I've yet to find a converter that has timing exactly like a real serial port. Know any with very exact timing(not bloody likely with USB)?

        Fortunately, most of our newer machinery runs on straight cat5.

        • Re: (Score:3, Interesting)

          by ScrewMaster ( 602015 ) *

          Yarg, I've got some industrial machinery that uses serial and I've yet to find a converter that has timing exactly like a real serial port. Know any with very exact timing(not bloody likely with USB)?

          Fortunately, most of our newer machinery runs on straight cat5.

          I'd guess you're running Modbus, or something similar.

        • A microcontroller intermediary would probably be the best way to go: PC -> usb ->usb2serial -> microcontroller -> serial -> machinery A bunch of PICs come with two built-in UARTs, and can be coded to do exact timing on the side where it matters.
      • by popeye44 ( 929152 ) on Sunday February 28, 2010 @12:09AM (#31302448)
        I work in an environment where we use Serial connections on Sprinkler controllers to Intersection battery backup and even traffic counters. We have multiple devices in which the usb to serial does not work. "multiple brands" Fortunately since most of our guys doing this type of work are outside daily in all weather. We started buying toughbooks around 6 years ago. As they are mil-spec they require that port. Imagine my surprise when I got a newer model HP 6730b and it had a serial port but no hdmi/displayport etc? It's the first serial on a brand name corporate laptop I've seen in a long while."However we are limited to which mfg's we can buy from most of the time" Serial needs to go. It's the fault of the obscure hardware mfg's that keep it around. Instead of designing something around USB.
      • The main issue is delay. USB is a complex standard, it requires more processing power on both sides to run, and it's not truly great for realtime applications.

        Certain simple electronic devices are just meant to be serial. Most PICs have built-in RS232/RS485 support while only few have USB support (and the very few are way more expensive.

        I was wondering the same thing the other day. Actually, the only thing that is dying is parallel output.

        Think about it:

        LPT got replaced by USB
        PCI (Which is parallel) got replaced by PCI express (serial)
        IDE/PATA got replaced by SATA
        Parallel SCSI got replaced by Serial SCSI

        But regarding serial devices, wether it's USB or the simpler and slower RS232, they are here to stay. They are cheaper, simpler to implement, and more effective. Computers will have UART chips as long as 3D routers, PIC recorders, home-made electronics, and other similar devices have RS232 ports.

        I believe we'll see RS232 for at least another decade.

        • Re: (Score:3, Funny)

          by Forge ( 2456 )
          According to some otherwise good SciFi (Stargate comes to mind) even alien devices use Serial.
    • Re: (Score:3, Informative)

      by dumb_jedi ( 955432 )
      Well, as a Electrial Engineer who designs equipment that have a serial console, I think I give you several reasons that the serial console will be round for some years yet.

      First, legacy. Most professional routers have come with a serial management console since ever. So anyone who's been trained to manage these devices use serial consoles for that. Of course, by being an IP equipment, you can manage them by accessing the same console using telnet, and you can upgrade their firmware using that console too.
  • ... about a decade ago.

    • by Anonymous Coward on Saturday February 27, 2010 @11:14PM (#31302060)

      Screw that. I do programming for embedded systems and serial is absolutely essential. Even the simplest bootloader supports standard serial. Hell, you can write an implementation of rs232 in an fpga in about 20 minutes. Its ubiquitous because requires no real software to make it work...and when you have barely any software working on a system, that uart can be the difference between hours and weeks of debugging.

      • Re: (Score:3, Interesting)

        by X0563511 ( 793323 )

        My phone (Palm Pre) can even pull bootloader code over USB, so even if the boot flash gets hosed, it can recover via USB.

        Serial shouldn't be needed outside of microprocessor development these days... that it is is sad.

        Sure, a board may cost $0.50 more to manufacture... yea, stop penny-fraction-pinching you bastards!

        • by Darinbob ( 1142669 ) on Sunday February 28, 2010 @02:39AM (#31303378)
          Serial is essential! It's cheap, simple, lots of hardware support it, and there's minimal firmware support needed for it. If you've got 8K RAM and runs at 1MHz, you don't want to waste it on a bloated USB driver. Serial port works from an interrupt context, so you'll be able to use it many times where USB can not work (say your OS is busted and you need to debug it).

          Serial port isn't used because we're Luddites, but because it works.

          Now if things had standardized on external I2C or SPI ports, that could work. But USB is just bloatware in comparison.
      • by Miamicanes ( 730264 ) on Sunday February 28, 2010 @12:25AM (#31302564)

        ^^^ Amen. For anyone into embedded electronics (including robots), real honest-to-god non-USB-bridged serial ports are pretty much the only port left on a modern PC (or at least a decent thirdparty motherboard in the form of an IDC header) that neither Windows nor Java can fuck up.

      • Re: (Score:3, Informative)

        by Anonymous Coward

        I've been developing for the Atmel ATSAM3U chip, which uses the ARM Cortex-M3 core. Its development board has serial ports, but I can reprogram the chip entirely, from full eraase, with just the built-in USB port.

        When erased, the chip boots off an internal ROM. That ROM, if yo have a 12 MHz crystal hooked up, will activate the USB 2.0 Device port and make it look like a serial dongle. You talk to the thing via /dev/ttyUSB0 and download the program top flash through it. As a final step, you run a couple

    • by Jhon ( 241832 ) on Saturday February 27, 2010 @11:48PM (#31302260) Homepage Journal

      I can't speak to switch access, but the serial port is paramount in the medical instrumentation field. Virtually all interfaces are serial. Need to hook up a CBC machine? Cobas? Vitek? Serial!

      Most machine shops -- their equipment is serial. Sending cut information to the lathe? Serial.

      • by Bester ( 27412 ) on Sunday February 28, 2010 @02:19AM (#31303262)
        Funny, I just walked around my ICU and everything is connected via ethernet. Monitors (philips), ventilators (dragers) and of course the computers (windows). Even the dialysis (prismaflex) machines hook via ethernet.

        The ultrasound has an ethernet cable attached as do the image intensifiers. The biochem lab also works over TCP.

        Certainly nothing major in the hospital that I work in uses serial connections.

        Maybe the older equipment used to use serial but given the amount of data shuttled around I don't think it would be feasible so use serial. Of course I can only draw experience from where I work, other hospitals may be different.

  • What do you mean 'serial ports are rapidly disappearing..' They're all but gone, aren't they?! :-/

    • Re:Serial Ports.. (Score:4, Informative)

      by unr3a1 ( 1264666 ) on Saturday February 27, 2010 @10:47PM (#31301852)

      He means on desktops, laptops, servers, and shit like that. Other than cisco routers and switches, you can't really fine hardware that has a serial port on it. But all routers and switches are still manufactured with serial...

      • Re: (Score:2, Informative)

        by Anonymous Coward

        "Other than cisco routers and switches, you can't really fine hardware that has a serial port on it."

        Every piece of DC-worthy gear I've touched has had serial.

        Of course, most stuff either comes with serial *and* ethernet, or allows one to hop in via serial and set up a web-based interface, but serial is always there.

      • Re:Serial Ports.. (Score:5, Insightful)

        by Anonymous Coward on Sunday February 28, 2010 @12:33AM (#31302616)

        Other than cisco routers and switches

        Are you serious? The only examples anyone on Slashdot can find seem to be routers and switches? The reasons RS232 isn't going away is because an awful lot of industrial automation equipment (large and small-scale) still uses it. Why? Because a) all of the existing industrial automation equipment uses it, so new equipment is designed to be compatible with existing interface and control systems, b) it has proven itself to be incredibly reliable over the years, c) it's cheap (in terms of money, but also in terms of the amount of supporting hardware required). Also, while it may not be fast enough to transfer huge firmware images or run high-bandwidth stuff like video over, it's fast enough for what it's used for. If a firmware update takes 5min to do on a $100,000 piece of factory equipment, so what? The company probably spent a month planning for the upgrade, and will spend a week testing it after the update to make sure it still meets performance and safety requirements before re-deploying it anyways. There are billions of dollars invested in RS-232 by some highly conservative companies that don't change things on a whim, when a complication arising from an unnecessary change could cause 5-figure-per-minute damages or loss of life.

        Why is RS-232 still around? Because it ain't broke, and it don't need fixin'!

    • Re:Serial Ports.. (Score:4, Informative)

      by interiot ( 50685 ) on Saturday February 27, 2010 @10:55PM (#31301928) Homepage

      When it comes to managing important network switches, no, they aren't gone.

      When an important switch fails for some reason, how do you contact it to see if it's recoverable remotely? (i.e. when your network admin has to manage switches that are located at remote satellite offices)

      Out-of-band management addresses this limitation by employing a management channel that is physically isolated from the data channel. []

      • Re:Serial Ports.. (Score:4, Interesting)

        by zappepcs ( 820751 ) on Saturday February 27, 2010 @11:53PM (#31302302) Journal

        An awesome point that can't be overstated. Well, probably not anyway. There are modems, converters, terminal servers and several other ways to use a serial port on important hardware. Out of band management is one of the best reasons for ever using it. The dial up modem as fall back to access servers has not been replaced yet. I imagine that there are a few reading these posts that know serial backup saved their bacon more than once.

    • by deniable ( 76198 )
      "the serial port is rapidly disappearing from new laptops" in full, and yes, they've been gone from most laptops for years now. We have to salvage old gear if we need to talk to a serial port. USB -> Serial mostly works, but not always.
  • Web Interface (Score:2, Informative)

    by DarkTitan_X ( 905442 )
    Most of the newer switches, routers, multiplexers and any other device with a serial port for a terminal interface I've had the pleasure of configuring had a web interface. I'd say that's the direction manufacturers are headed and is the next logical step.
    • Re: (Score:3, Insightful)

      by hedwards ( 940851 )
      I might be missing something, but that's not an adequate substitution. The point of a serial console is for when something goes wrong and for some reason the configuration is broken. In situations like that a web interface doesn't do you a damned bit of good because you can't access the box directly via the internet. Watchdog hardware or remote reboot hardware can get the box back up, but without a good serial console you're not likely to be able to fix the problem without being there.

      With a serial conso
      • Re: (Score:3, Insightful)

        by Idiomatick ( 976696 )
        Directly link through a cat5 port?
        • Re: (Score:3, Insightful)

          by Anonymous Coward

          You might want to understand the amount of things that have to be running correctly to even have a working TCPIP stack to make it unpractical as a debugging tool.
          For a serial port, you could be talking to it in less than 10 line of non-interrupt C code in a pre-boot environment if you have to.

    • Re:Web Interface (Score:4, Informative)

      by jonwil ( 467024 ) on Saturday February 27, 2010 @11:13PM (#31302048)

      As someone who has worked with Cisco routers running IOS, I can tell you that there are plenty of situations where a console cable (which plugs into a serial port) is essential.

      • Re: (Score:3, Insightful)

        by BitZtream ( 692029 )

        You should also point out that no serious network administrator has a web server enabled on his/her routers and switches.

        That crap is fine at your home where it doesn't really matter if something gets exploited, but no self respecting router/switch flunky on the planet leaves the web server running longer than it takes to get a console hooked up, login, enable, and turn off the damn webserver.

        Then you go setup the device if you don't have a auto-config system setup.

    • by deniable ( 76198 )
      Web interfaces are all well and good unless you're having to configure IP on the device. Fallback to DHCP is good, unless you have a device that somebody's configured wrong and needs to be corrected.
  • Simplicity (Score:5, Insightful)

    by ak_hepcat ( 468765 ) <leif@[ ] ['den' in gap]> on Saturday February 27, 2010 @10:48PM (#31301856) Homepage Journal

    It calls out to you.

    The great thing about a serial console is that it doesn't take long to figure it out. And you only need 3 wires to get there.
    Another nice thing about it is that it's point-to-point, so you don't have to worry about your signals getting lost.

    Heck, you can create a serial interface from discrete components if you're really into fun.

    So use your serial console for what it's intended to be used for: emergencies and initial configurations.

    • Re:Simplicity (Score:5, Informative)

      by darronb ( 217897 ) on Saturday February 27, 2010 @11:13PM (#31302056)

      Simplicity really is the key.

      Just a few days ago I hacked together a 9600 baud serial output in like an hour to help me debug an embedded microcontroller design using only a single IO pin and a crude spin-delay based bit-bang function. It worked great, and I found the trouble.

      There's no way you could add something like USB nearly as easily. FTDI makes some great chips / cables, but at the microcontroller it's still TTL-level serial IO.

      Plenty of microcontrollers have lots of extra serial IO ports. Many are adding USB ports as well, but it takes an absolutely stupid amount of firmware to make USB work.

      There are several microcontrollers I can do USB for, since I've done it before. However, it takes weeks of work to implement USB the first time on any new microcontroller. It's usually really prone to bugs, too. USB is just too complex for the simple dumb pipes that most embedded developers need. On top of that... most of the time the micro vendor's USB firmware examples just barely work, and aren't designed very well so they're very hard to modularize and include in another design.

      • Re: (Score:3, Insightful)

        by Eskarel ( 565631 )

        The problem is though that it's only simple if you have an actual serial port on both ends.

        The serial port is all but gone on laptops and not exactly common on desktops or workstations. That isn't going to change any more than lpt ports are destined for a comeback.

        Yes adaptors exist but the drivers for them aren't by any means standard and I know that most of them don't work under windows in 64 bit. Add to that the fact that putting an incredibly complex software driver(which is what it is) to implement a "

    • Re: (Score:2, Insightful)

      Another feature is software simplicity. This may not be an issue for the laptop, but it is an issue for the embedded system. Or it can be during development.

      USB is a complex protocol which requires a fair amount of code and data structures to support. A serial port on the other hand requires less than a page of code (in it's most simple form). The result is that when a system crashes, a serial port has a much better chance of being operational than a USB interface. Many systems with serial ports are de

  • It just works (Score:5, Insightful)

    by mtmra70 ( 964928 ) on Saturday February 27, 2010 @10:49PM (#31301870)
    I upload firmware and program various devices at work via USB or TCP/IP - and it is great because the connections are fast. However, when something goes very wrong with the devices, the RS232 port always works. Also, being able to get serial data just by listening to a couple pins is far easier than trying to deal with USB connections/drivers you have no clue about.

    When it comes down to it, serial works, its easy and it's a life saver.
    • Re: (Score:2, Interesting)

      by emt377 ( 610337 )
      A lot of boards these days are populated with FTDI FT232 chips or comparable. [] Usually using a separate 'console' USB port separate from the host/device ports provided in addition. Pretty much every desktop system comes with FT232 drivers, so all that's needed is a cable, or possibly an INF file or similar if they use a nonstandard MID/PID. Eventually we'll probably see these on-chip on SoC devices that already have USB support. But RS232E is quite practical
    • Re:It just works (Score:4, Insightful)

      by 0100010001010011 ( 652467 ) on Saturday February 27, 2010 @11:15PM (#31302076)

      My SheevaPlug [] has a mini-USB connector on it. It's near impossible to brick. I even did a dd /dev/zero to the entire flash memory and was still able to get to the JTAG interface with a USB cable to my MacBookPro.

      "Serial" shouldn't go away, but the massive plug should.

  • The latest-generation Cisco devices are switching to USB for console communications. So it's starting to happen...

  • No. (Score:5, Funny)

    by Dr. Evil ( 3501 ) on Saturday February 27, 2010 @10:52PM (#31301890)

    It will never die. It will be around forever. Technicians, thousands of years from now will have to interface with wireless psychic rs232 adapters so as to configure their Cisco hyperdrives.

  • UARTs are cheap... (Score:2, Informative)

    by Anonymous Coward

    As an embedded device engineer, I love good old UARTs. They are very small cores to add to an FPGA design, simple to write a driver for, and fast enough for most simple debug applications.

    Trying that with a USB core is not an easy prospect. And they arent *that* slow. The free UARTlite IP core from Xilinx can run up to 921,600.. plenty fast for most things embedded...

  • As long as (Score:5, Interesting)

    by phantomfive ( 622387 ) on Saturday February 27, 2010 @10:52PM (#31301902) Journal
    It will exist as long as it is useful. Right now, people are still finding it useful, therefore it still exists. You still see ISA ports around sometimes.
  • RS232 port utility (Score:5, Informative)

    by Announcer ( 816755 ) on Saturday February 27, 2010 @10:55PM (#31301922) Homepage

    I work for a small electronics manufacturing company, []
    and we make a number of devices that use the serial port. In recent years, we had to start including USB-serial adapters with every device for the very reason mentioned: Many newer computers simply do not have RS232 ports anymore.

    The RS232 port is a very convenient way to connect with a number of peripheral devices that don't need much bandwidth. In most cases, 9600 BPS is plenty. You also have the "handshake" lines which can be used to toggle an external device on or off. We use it to drive an LED and an opto-isolator to key a ham radio transmitter, among other things.

    As long as there are low-bandwidth, human-interface devices, there will still be SOME use and purpose for the RS232 port.

    • Re: (Score:3, Interesting)

      by usul294 ( 1163169 )
      right on, two recent projects I've done, one my senior design project, and my first professional job had me using RS-232 to connect a laptop to an embedded system. If the host machine only needs to see a single floating point number a couple times a second, RS-232 is plenty fast enough, and is much less time consuming from a design standpoint than say a TCP/IP connection.
  • Easy to design in (Score:5, Informative)

    by jimmyswimmy ( 749153 ) on Saturday February 27, 2010 @10:58PM (#31301946)
    I still design lots of equipment with serial interfaces inside. It is much easier to connect to a low-end microcontroller which may barely have even a single UART. And even for a higher-end processor, it's so much easier to build the interface. Developing a USB interface requires a pretty detailed understanding of USB - selecting endpoints, which transfer protocol to use, etc - so there's a big software investment and often a significant additional hardware investment to implement a USB interface. Serial is often damn close to free, so easy that it's a no-brainer to put in. And for ethernet devices like switches I can't imagine why anyone would want to bother with a USB interface when you already have 8/16/48 copies of an ethernet interface available, just plop down yet another copy of the ethernet PHY design and make that your console interface.

    Point is - serial's EASY to give you, so you're gonna keep getting it for a while.
  • by CajunArson ( 465943 ) on Saturday February 27, 2010 @10:58PM (#31301948) Journal

    I actually posted an Ask-Slashdot [] about running a headless Linux Box that didn't have any serial ports... my question was about what happened in the 5% of cases where I couldn't SSH to the box (like if a kernel upgrade goes south). The basic answer was that I still needed a serial terminal. Oh, I know that USB can be used as a substitute, but the problem was that USB required a booted & functional kernel with a working USB stack to emulate the serial line. I recently saw a similar discussion in comments about how bad the old-school serial terminal code that is still in the Linux kernel is. Many people incorrectly thought the poster was saying that Linux shouldn't have a command line interface, which was completely wrong. The poster instead raised the (excellent) point that complicated and buggy software emulating long-obsolete device interfaces may not be good for the Kernel (CLI is NOT the same as a terminal interface).

    Are there damn good reasons why RS-232 serial ports should be dropped from modern hardware? Hell yes, not the least of which is a 3-15 volt swing signalling protocol is an invitation to fry the low-voltage electronics on modern systems. However, the CONCEPT of having a box that does not require any type of graphics, or even a working network interface, is still very useful. So... what are the better technologies to accomplish the same goal without having to rely on antiquated hardware implementations?

  • As previously stated - there are exceptions, such as using USB - granted, all this is doing is putting the USB-to-Serial converter *inside* the piece of hardware - as your PC/laptop is treating it as such - and giving you "serial" access to the device.

    As for the "greater" question, as will Ethernet/Network/Web interfaces ever surpass it - I will contend, the answer is no - or not any time vaugley soon.

    I used to own a company that made NAS appliances - back many many years ago. When you had a "plug-and-p

  • No (Score:5, Informative)

    by dindi ( 78034 ) on Saturday February 27, 2010 @11:05PM (#31301992)

    Serial is cheap, simple, works really well, and you can hook up 15+ year old equipment to it with no problem.

    Is it slow? Not really, but firmware updates should be through TFTP or HTTP by now anyways for larger files.

    Complicated wiring? RX-TX TX-RX, common ground.

    Also RS-232 has many brothers and sisters like:
    RS-422 (a high-speed system similar to RS-232 but with differential signaling)
    RS-423 (a high-speed system similar to RS-422 but with unbalanced signaling)
    RS-449 (a functional and mechanical interface that used RS-422 and RS-423 signals - it never caught on like RS-232 and was withdrawn by the EIA)
    RS-485 (a descendant of RS-422 that can be used as a bus in multidrop configurations)

    On the USB console: yeah, you can have a USB console. Most like there will be a FTDI chip, which will make your USB into a serial connection. Want an example? Arduino.....

    By the way, the post is kinda mis-worded.... USB is a serial bus, so a USB console is technically a SERIAL console :)

    • by AK Marc ( 707885 )
      RS-485 (a descendant of RS-422 that can be used as a bus in multidrop configurations)

      I never heard of it being used as that, but it's always used when the distance is long. I've even deployed 232 to 485 to 232 setups to get RS-232 gear separated but 100+ feet to work. But usually, it's ODU gear with an RS-485 port because they expect to be installed a long distance from any controlling device. Then it's just a single indoor adapter to plug it into a PC. Where's my serial port on my PC that's selectabl
    • Re: (Score:3, Informative)

      Unfortunately, every untrained technician and their ill-trained supervisor gets these wrong. The flow control lines are not there for laughs: mis-handled, they lead to many unfortunate adventures, at the worst moments. I've had to deal with the errors when someone thought the way you did, failed to connect the flow control to anything, and wound up with jammed serial lines.

      The standard is published many places, such as []. Even your "three wire desc

  • by ss_teven ( 569013 ) on Saturday February 27, 2010 @11:19PM (#31302096)
    I work in the offshore survey industry (oil/gas industry), and 95% of products to date still come with serial ports. They are critical for our purposes, and onboard com ports are a must for timing critical jobs such as multibeam bathymetric surveys.

    Current project im working on we are using Moxa multiport serial boards w/ 32 serial ports on this pc with around 25 currently inuse for IO. (Historically used Digi boards but they were awful for timing (relatively!), 30ms delay compared to the near 0ms on the Moxa units.)

    Simple to use, easily available, and cheap. Almost all the devices I work with use standard parity/stop bits etc, just varying baud rates, which is easy enough to remember.
  • Too late! (Score:5, Funny)

    by macraig ( 621737 ) <> on Saturday February 27, 2010 @11:20PM (#31302100)

    I attended its funeral yesterday. It was an open-casket ceremony, and people just couldn't seem to resist fingering the deceased. Sadly it didn't respond.

  • USB console (Score:3, Informative)

    by tftp ( 111690 ) on Saturday February 27, 2010 @11:23PM (#31302120) Homepage

    Is there any sign on the horizon of a USB console connection?

    There is no standard USB device class for serial adapters. There is communications device class, but it is huge and doesn't really help. So FTDI and Cygnal and others have to write their own drivers for tens of OSes and architectures. If you walk up to a device with a laptop and a USB cable, chances are that your laptop doesn't have a proper driver. To make things worse, many USB-Serial adapters have to use their own VID/PID/REV identifiers, and that makes it even harder to recognize the device. Class-compliant devices would "just work" like a USB drive does, or a mouse.

    There is also no standard API in OSes to talk to *modern* serial devices. USB serial devices are emulated into a virtual COM port.

  • by Foredecker ( 161844 ) * on Saturday February 27, 2010 @11:27PM (#31302142) Homepage Journal

    I understand what you are saying: RS232 ports suck for any number of reasons.

    But there are a few why it is still often used.

    First, it has been ubiquitous for 20 to 30 years. When I started my first development job in 1982 - everything talked to everything else via RS-232. Back then 9600 baud was considered fast. At 8 bits per character with no parity and one stop bit, 9600 baud could paint a screen with characters in one second. Yes, we thought that was fast. Things got better as baud rates improved - but RS-232 remained everywhere - it was the one constant universal interface. Even though it is incredible antiqued, it is still in many PCs.

    Second, RS-232 (and its many cousins like RS-422) are very, very easy to use in software. The simplest I/O can be done in a few lines of code. Its easy to put RS-232 code right in firmware. This makes it easy to write bootstrapers, boot consoles, debug consoles etc.

    USB would be a poor choice for a replacement. The reason is that it isnt peer to peer - it is a master/slave architecture. There is always one master -usually a PC, and one or more slaves (keyboards, mice, printers, scanners, cable modems, disk drives, storage keys, cameras etc).

    It requires a special cable to make to client USB devices talk to each other. This cable has a small do-dad that looks like a master to both ends. This works ok, but it requires special knowledge of this USB end point to work correctly. Note, Windows began to support this in Vista for migration. Its called Windows Easy Transfer/a>.. There is a version for XP too ( []downloadable/a>). It actually works very well, but the cables were not cheap. Note that the cables really are not cables - but a dual-headed master USB controller with two ports - it just looks like a cable with a lump in the middle - [] Belkin sells one for $40 [].

    LLike a few other posters have said - USB is much more complex to use in software than simple RS-232. Ive written code for it and I find it more complex than Ethernet at the MAC level.

    I think Ethernet is the real replacement. A little TFT or Telnet server / client is really trivial to write. This can (and often has been done) in firmware. For example, most (all?) home Ethernet and wireless routers dont have a serial port. Their management is over Ethernet - works great.


  • they need to use SD card / usb keys for firmware / base / fallback config. just put in a small eprom with a base boot code that can reed a usb key to upload the firmware. The SAM system is build like this and is a lot easier to update then burning new eprom for full code updates.

  • by SharpFang ( 651121 ) on Saturday February 27, 2010 @11:44PM (#31302238) Homepage Journal

    RS232 is easy to program. If it's a switch without OS or some other embedded device, RS232 is the easiest and fastest way.
    Sure on the PC side there are the problems of baud, parity and so on. Thing is on the device side you can get a working bidi buffered transmission within 30 lines of assembler (100-200 if you have no UART and need to push each bit yourself). Writing equivalent of "hello world" over USB becomes kilobytes. And if you go into a web interface, you quickly lose enthusiasm as you realize on top of CGI you need to write the web server, the TCP stack, the IP stack, and if you're unlucky, the Ethernet protocol stack (in VHDL) as well.

    On top of that, a thousand things can go wrong in writing USB or Ethernet or whatever. RS232 is rugged, fault-proof, it works from moment zero. You will be able to communicate with bootloader which has no idea what ethernet is, you will be able to diagnose faults when 90% of essential peripherials are fried, and if the cable goes loose, just move it around a bit and the connection will be back, no timeouts, no disconnects, no "intelligence" to get in your way.

    And if you open various devices that use USB instead of serial, you will find a neat little FDDI, Profilic or such chip connected to the USB interface. The devices really connect over RS232. They just have the "RS232 over USB dongle" built in.

  • by rcpitt ( 711863 ) on Saturday February 27, 2010 @11:49PM (#31302272) Homepage Journal
    Telus - local ILEC - is installing ~$100k worth of hardware in all the local SAC boxes to allow them to run TV over the local loop at 15Mbps.

    Guess what every SAC box has strapped to the back of the equipment rack - a US Robotics full-size (about 12"x7"x1") Courier modem!

    Damned if I know where they're getting them from - but there they are...

    • Re: (Score:3, Funny)

      by Anonymous Coward

      We buy those all the time for OOB redundancy. 56k US Robotics modems run about $300 now though. Pretty funny as I used to have boxes of the old 28.8 and 33.6 ones from when I shutdown a modem bank that I recycled. Now I get to put in purchase orders for 10 modems at a total of 3k. Always makes me laugh.

  • If you exclude the TxD and RxD (and Ground) lines, there are still 6 others, which are trivial to interface to. YOu get 4 inputs and 2 outputs, to which you can connect switches and LEDs directly. Then use setserial/statserial to control/monitor the logic levels. This is actually quite useful sometimes.

  • The great thing about a serial port is it's simplicity from a programming standpoint. Since console access is needed for diagnostics (that is, something is already wrong), the less it depends on, the better.

    Most of the problems can be fixed by having vendors not all use different and OH-SO-SPECIAL pinouts for the serial connection and a dirt cheap USB Serial port for the laptop.

  • I can't recall the last time I saw a serial port that wouldn't accept 9600 8-N-1. Not in a couple of decades.

  • by narnian ( 9597 ) on Saturday February 27, 2010 @11:57PM (#31302338)

    With the increasing complexity of network devices - switches, routers, load-balancers, firewalls, the expectancy of a functional terminal console puts a good design constraint on system developers. If they have to provide the ability within a 80x24 terminal funtionality to configure, operate and maintain a such a device it is a good thing. A good management is useful in providing an overview of the configuration and helps provide linkage to the management of components.

    A serial terminal console is good because:-

    * It enforces the designer to limit the presentation of management information to the 80x24 screen (possibly using pages), and often with a 9600bps data rate. My view is if they can't do it properly in a console they have not though well enough about management. Too often GUIs for management tend to hide important configuration parameters away.
    * A terminal console allows easy copy-and-paste and script munging of configurations to ensure consistent deployment. GUIs don't allow such duplication of configurations very well.
    * It allows simple out of band management through the use of a terminal server connecting multiple consoles. Such a simple management connection provides am always available management window in a network down situation. (Assuming this is deployed properly). You can also manage the risk well if management can ONLY be done by serial (preventing the management network inadvertently being connected to a production network.
    * While standarardisation of the physical port (male or female DB9 or RJ45) and host type (DTE or DCE) and even hardware handshaking is right royal pain. At least it is usual possible to determine it after a minimum number of tries. But essential it is pretty straightforward to implement.
    * While a USB connection sounds good, I would only prefer it if it was guaranteed to be a zero driver installation.

  • You young whippersnapers and your newfangled serial consoles.

    Back when men were men, this is what a manly console looked like; []

  • by fuzzyfuzzyfungus ( 1223518 ) on Sunday February 28, 2010 @12:54AM (#31302734) Journal
    Outside of Real Serious Stuff(if your job involves oil rigs, SCADA, legacy devices that Google has never heard of this probably means you), I strongly suspect that "serial" in the sense of "DE-9 or DB-25 connector that won't freak out when exposed to the full +/- 12(or even a touch more in some cases) volts that serial used when men were men and cable runs were long" is not so long for this world, outside of a few legacy niches.

    On the other hand, "serial" in the sense of "a few pins carrying something that looks like rs-232 at whatever voltage this device's logic runs at" or "device has a USB connector; but that just means that they slapped an FTDI or Prolific chip on a serial design" will be more or less immortal. Even in high volume consumer devices, where it isn't supposed to be user accessible, you can generally find a logic-level serial connection somewhere, though it may not be labeled or have any sort of connector soldered in. It costs almost nothing and can save you from having to JTAG your way out of (most) of your mistakes. When designed to be accessible, it is ideal for dealing with initial configuration for devices that communicate primarily over ethernet.
  • RS232 is fee-free (Score:5, Interesting)

    by Andrew Sterian ( 182 ) <> on Sunday February 28, 2010 @01:18AM (#31302930) Homepage

    From a device manufacturer's point of view, RS232 is free to implement. No special drivers are required on the host.

    Now, for USB, you have to either pony up $2000 PER YEAR to the USB implementers forum to get your own VID/PID and distribute a driver to your customers (and deal with the resulting customer service issues) or add a chip from FTDI (or similar) and piggyback on their VID/PID but then ask your customers to download and install a generic driver that does not specifically identify your hardware.

    Gimme RS232 any day.

  • It's okay (Score:4, Insightful)

    by jones_supa ( 887896 ) on Sunday February 28, 2010 @02:11AM (#31303228)
    Not all hardware has to be thrown into garbage just because it's old.
  • by mirix ( 1649853 ) on Sunday February 28, 2010 @02:15AM (#31303246)

    This machine has 11 UARTs on it, 4 of them are RS-422, the rest are normal 232.

    I've got a couple 232 lines to other puters in this room, and a router.
    RS-422 goes down to the basement, and controls the machines down there, ethernet or not.
    There is a getty running on one, in case I get too drunk and smash the monitor.

    I use the remainder for connecting to my microcontroller projects and programmers, etc.
    You can run it on *ancient* hardware, with no resources. It's incredibly useful for debugging microcontroller programs.
    Things that only have 128bytes of RAM, and a few k of program rom...

    You can hook it up to a 40 year old TTY and it will work.
    You can haul a dumb terminal out from a cave and it will work.
    You can short every pin of the serial port together, leave it there for a decade, come back, and the bloody thing will still work.

    I'm a rather miserable programmer, and serial is a bloody cakewalk to interface to. USB, on the other hand, isn't quite as simple.
    And it's a *standard*. Man I love things that are standardized.

  • by Comen ( 321331 ) on Sunday February 28, 2010 @09:03AM (#31304888)

    I think the DB-9 connector is a little big for what its doing though, I mean even a DB-15 monitor type connector is duplo size for 15 pins.
    Maybe I just like Cisco to much, but it would be nice to have everyone just use the Cisco RJ-45 spec for serial connections, I hate when other router/switch vendors use RJ45 but the pins-outs are totally different so you have to find that special DB9 to RJ45 adapter for that 1 piece of gear, instead of using 1 of the Cisco adapters that you have laying everywhere.
    Even if on the back of laptops they used RJ45 for serial and marked they would keep it around longer? the DB9 connector seems to big realistate wise to me I guess.
    Then you could just use a regular RJ45 cable to connect between the 2, no need for some non-standard cable.

    Also for those of you that use console servers allot, I still think the older Cisco access servers that many use for console servers now a days are better than any of the Linux server type solutions I have tried. The Cisco access devices supports telnet to each port, a real routing table that supports multiple gateways via static or even routing protocols like OSPF etc... also Tacacs+ auth if you need that.

    • Re: (Score:3, Interesting)

      by adolf ( 21054 )

      That's nothing.

      I used to have an 8-port BocaBoard (on a 486 PC which I stubbornly configured to have 14 working serial ports, just because).

      It used 10-pin connectors (RJ-48?). At the time, Ebay didn't exist, and the tooling to put the connectors on was rather expensive, and 10-conductor flat lead was hard to find. You'd think, though, with 8 pin cabling being common, and RS-232 only ever really needing three, five, or seven pins (8 with RING), that they'd have included the most useful lines toward the mid

interlard - vt., to intersperse; diversify -- Webster's New World Dictionary Of The American Language