Do you still use "RS232" or something else?

Hello All,

although most of our (industrial) clients still use to have computers with a "real" serial port, I observe a small but increasing number struggling with bad USB adapters and asking for other interfaces.

Therefore I'm reconsidering the best suited interface for device configuration and diagnosis.

Do you still use EIA-232? Customers complaining?

What do you consider a suitable "successor"?

  • USB. Can be even cheaper than EIA-232, and AFAIK a HID doesn't require administrator rights for "installation". But we have to supply software to the user (cost, distribution) and there remain some traces on the host system.

  • Ethernet, TCP/IP, HTTP, DHCP or Zeroconf? Every recent computer has Ethernet and a web browser, so the user needs no additinal components besides a patch cord. But if he wants to be connected to a(nother) network, there might arise problems. And the cost of Ethernet connectivity is higher than EIA-232 or USB.

More alternatives?

Oliver

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Oliver Betz, Munich
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Reply to
Oliver Betz
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I am going Ethernet - tcp/ip, VNC (RFB) access to my stuff - this leaves the communication to whatever is at the other side to the pixel/mouse/ keyboard level. Latest thing to be proudly shown:

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(board can be seen at
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) In fact it has an RS232 but it is only for internal purposes (debugging on failed network etc.).

Of course networking - especially of you maintain the entire thing locally and access it over VNC - takes up more resources, but often it is justified, e.g. in this case there is so much DSP-ing to do at peak load that the VNC &tcp load is a small fraction of the overhead.

Dimiter

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Reply to
Didi
[...]

[...]

this uses Ethernet for the _main_ operation. That's different from what I wrote ("device configuration and diagnosis").

Oliver

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Oliver Betz, Munich
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Reply to
Oliver Betz

I have see software distributions on USB FLASH drives, including one that convinced the WindowsPC that it was a CD-ROM with an autorun.ini on it.

No, it's not the cheapest solution, but there are a lot of things that you can do with it. Autorun, Boot from the USB, big file distribution, etc., etc.

RK

Reply to
d_s_klein

Actually it does both. You JTAG program the flash, boot off the "ROM" disk and off you go. Devices ship such that the user can turn on "support" in which case they connect to a listening vnc here etc.

Dimiter

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Reply to
Didi

Hello Oliver,

Yes, definitely.

Sometimes - but when it comes to talking about cost, they all agree to RS-232 again. :-)

There is none. RS-232 is by far the cheapest standard communication you can get, and it works perfectly fine even with the smallest microcontrollers.

Sometimes, USB is an alternative.

We tend to implement RS-232 (sometimes RS-485, sometimes USB - depending on the customers requirements) connectivity for configuration and diagnosis even in current developments. After all, the devices are build in some (smaller or larger) series, while you need the diagnosis tools only once (or a few times). So it makes perfect sense to keep the interface in the series devices as small and cheap as possible.

If people want to access the devices by any other means, there are adapters for every flavour of communication (USB, Ethernet, GSM, ISDN and whatever you like). RS-232 always is the least common denominator.

Ethernet generelly is not an alternative: Far too high power consumption, far too high ressources requirements (resp. wasting), too expensive. I would use Ethernet only if it was needed in the design anyway.

Tilmann

Reply to
Tilmann Reh

Diagnostics should work even if everything else failed to work. As far as diagnostics only, the RS-232 is the best interface; as it requires really nothing from hardware or software to operate.

Ethernet with HTTP server implies "large" system just to support this functionality. Basic Ethernet + UDP + proprietary PC software for configuration is relatively lightweight; but there will be the problems as they will be trying to connect to the device via their network.

If the cost permits, I like USB/RS-232 FTDI solution. It combines the best of USB and RS-232.

Vladimir Vassilevsky DSP and Mixed Signal Design Consultant

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Reply to
Vladimir Vassilevsky

Rarely as often I leave 232 available and have serial-USB bridge chips Silabs/FTDI as well.

Depends on size and complexity of device, large processor with available horsepower then ethernet, less horsepower add either a USB bridge chip or ethernet module.

In basic hardware and cabling terms yes, but also depends on distances require administrator rights for "installation". But we have to supply

Don't even get me on the which OS can be supported or not and which driver on the host and if the driver works well if more than one USB device of same chip family installed (because of something else). Let alone issues of driver versions.

If a larger number of devices, or longer distances in can sometimes be easier to integrate into customers network and no extra cabling.

It all depends on the type of equipemnt, market, where you can diagnose it from, how many, and so many other factors including the customers expectations, or internal de facto standards.

--
Paul Carpenter          | paul@pcserviceselectronics.co.uk
    PC Services
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Reply to
Paul

For the testbench I got a couple of FT232RL breakout boards from Sparkfun, attached wires with test clips to TxD, RxD, and ground. During development I can dump any kind of diagnostic data from any chip with a spare UART into any kind of program running on my desktop or laptop. Very handy.

Mel.

Reply to
Mel

You can buy USB cables with the FT232RL build-in directly from FTDI! USB end plugs into a PC, the other end can be bare wires that go into a breadboard.

Reply to
Jaded Hobo

Hi Oliver

I have embedded my comments.

Unfortunately - yes.

Low-power ethernet supporting IEEE 802.3az (optionally with IEEE

802.3af/at support)

Get the "best" of both worlds - EIA-232 (and RS485 ! ) over USB - using FTDI chips e.g. FT232RL.

Has free drivers for the main platforms:

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Dump "null-modem", 25-pin, 9-pin, 8P8C and 10P10C for EIA-232.

Awkward speed selection and handshaking options (use nothing, xon, xoff og hardware? The different wiring schemes combined with - that e.g. Nortel, HP, Cisco, UPS, Trapeze and Juniper have their own wiring and different plugs!

EIA-232 autonegotiation sucks and does NOT negotiate handshaking features and other (missing, damaged or present) hardware signal wires

- and is even asymmetrical (RTS, CTS) ! - it all eats your time and patience.

EIA-232 transport is only byte oriented - not packet oriented; so it is inefficient when evaluated with todays needs.

EIA-232 is unbalanced and therefore has very low common-mode suppression. The different signals interfere with each other, if the cable is longer than approx. 5 meters.

IrDA?

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Quote: "...Transmission rates fall into various categories: SIR, MIR, FIR, VFIR, UFIR, and Giga-IR...."

Reply to
Glenn

...

...

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combine it with a DHCP-server and client.

If the client can not find an existing DHCP-server - your hardware starts it own (but shut it down if another DHCP-server is detected). Then a mgmt pc will eventually get a ip-configuration.

Reply to
Glenn

Ethernet must have:

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so an awkward crossover cable is not needed.

Reply to
Glenn

I noticed this

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-Simplifies-0001

I've not used these, but they claim

["'The new CP2110 and CP2112 bridge ICs comply with the USB-HID class specification natively supported by most operating systems, thus removing the need to install drivers. This eliminates the risk of incompatible and exhaustive driver updates and obviates the need for customers to provide companion CDs with specialized driver information or to maintain download sites for driver updates"]

Is that enough for ("device configuration and diagnosis"). ? [I see they side-step mention of ones software..]

I also see the new NCT6681D from Nuvoton, (128 pins seems std size)

["NCT6681D is the first IC of Nuvoton`s new product line, or eSIO, which combines a built-in microcontroller and traditional legacy SIO functions. NCT6681D supports a rich set of features and targets the All-in-One PC applications, high-end motherboard applications that need the built-in microcontroller to fulfill the customized features, and any other applications that microcontroller can better execute the performance."]

includes this

["LPC interface, Printer Port, 2 Serial UARTS and KBC "]

So it looks like RS232 is not a complete dead duck just yet ?.

Of course, a vendor has to decide to use this device, and to fit RS232 connectors/level shifters and the latter is most likely the stumbling block....

-jg

Reply to
-jg

Maybe combine ethernet with LVDS-like signaling:

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Quote: "...For example, the static power dissipation in the LVDS load resistor is 1.2 mW, compared to the 90 mW dissipated by the load resistor for an RS-422 signal...."

Reply to
Glenn

October 08, 2008 Gigabit PHY IC Complies With Energy-Efficient Ethernet Guidelines

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PEF-7071
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Quote: "... XWAY-PHY11G is the first IC on the market to implement the Energy Efficient Ethernet (EEE) guidelines, which are based on the upcoming IEEE 802.3az standard. The Infineon PHY reduces its energy use by up to 90 percent (50 mW instead of 500 mW) during periods of idle ..."

Reply to
Glenn

Supplement:

Thanks for all replies.

Since several people voted for USB - UART adapters, usually FTDI FT232 flavour: That's also my preferred solution for people not being long-sighted enough to by a suitable computer with a real comm port.

But I suggest this only as a solution separate from my device (not integrated), because the installation requires Administrator rights, IOW is much more intrusive than I want one of my designs to be.

Oliver

--
Oliver Betz, Muenchen (oliverbetz.de)
Reply to
Oliver Betz

HID is the way I would go if I wanted to offer USB, because it doesn't need driver installation.

And the Silabs is a simple option / alternative to EIA-232. Cost is similar to an EIA-232 driver.

Depending on production volume, it can be cheaper to use a microcontroller with USB and own HID stack.

But although I didn't need to bother the customer with driver installation, I had to supply host software for every operating system my customers use. Currently Win32 seems to be enough, but I had to be prepared to offer the software for Linux and Mac.

With EIA-232, I can tell the customer to use the terminal software he hates least, readily available on every system down to my HP48 calculator or an old Palm pilot.

I also think so. But I keep the USB HID in mind as an option.

Maybe someone even makes a "terminal program" for the CP2110 some day, if not we had to do so.

Oliver

--
Oliver Betz, Muenchen (oliverbetz.de)
Reply to
Oliver Betz

Others have made a fine job of considering the technical issues so I'll restrict myself to the user perspective here.

RS232 runs can be fairly long - 100m easily enough over regular Cat5 cables. USB is a complete non-starter over that kind of distance meaning the equipment and computer need to be located together. That isn't always convenient.

RS232 with a CLI interface does not depend on anything special on the host computer - just a terminal emulator. That means I can use any machine that comes to hand and I don't need to track down and install software first. If it's a twenty year old bit of kit I am not dependant on the manufacturer still being in existence and providing new software for a modern OS. Of course a CLI needs more space than something that simply downloads a new configuration in a fixed binary format but that may be a matter of a kilobyte - probably less than you need to implement USB or a TCP/IP stack before you even think of your application-level processing.

RS232 is still ubiquitious in many applications and there are many methods of handling it. A simple use may be direct connection to a PC but dial in use becomes a possibility for remote access, and at the high end there are the consoles servers from Cyclades and the like for those that have to manage dozens of devices in a robust, organised manner.

As for the quality of USB-serial adapters, if you keep to a couple of simple rules you shouldn't have any issues. First of all, if you use an RS232 port make sure you actually use RS232 - it is a serial interface, not a GPIO port. (Ab)using handshaking pins to do something they were not intended for is always going to be asking for trouble.

The other potential gotcha is with break handling. In my view it is unforgivable that there are adapters that can't send a break signal but they are out there - bear that in mind at the design phase so you never need a break and it simply won't be an issue.

On a purely personal basis I'd much rather see an RS232 port that I know I'm likely to never have issues with, rather than a USB interface that depends on a vendor supplied app that may be useless in five years time. Network configuration is slightly better but that depends on how the initial network config is done (IP address and netmask). A DHCP client depends on a network running DHCP in the first place, and anything that initially sets itself up as DHCP server (like most home routers) can't be connected to a production network until they are configured.

--
Andrew Smallshaw
andrews@sdf.lonestar.org
Reply to
Andrew Smallshaw

ahh, that's seems good. I'm using the CP2102 right now, but it's true that the need to install a driver is quite annoying. I'll check it out :)

Thanks Bye jack

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Yoda of Borg am I! Assimilated shall you be! Futile resistance is, hmm?
Reply to
Jack

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