RS-232 - still alive and well

[NiHaoMike]

Who else expected a young Chinese girl to not only know what it is but also why it's good to have?

[DiTBho]

Just looked at the title, yes, I have recently Japanese laptop and found the RS-232 is still alive and well, but that girl on Youtube ...

[T3sl4co1l]

Well, I expected her to?

She's been around for, let's see, 2015 at least, don't remember how many years before that?  Her appearance is unconventional, I suppose you might say, but she's got lots of electronics/programming/hacker/maker experience.

I haven't followed her career much, but she's definitely out there doing real projects.

Tim

[SiliconWizard]

Yeah, she sure is showing a lot of boobs, but she's doing real stuff and has become pretty knowledgeable. So, hey, why not.

As to RS232, I haven't used that in over 15 years or so.
If I ever have to occasionally connect to a machine through RS232, I'll just buy a USB-RS232 adapter. But hey.

[Siwastaja]

I use classic asynchronous serial (UART) a lot but not RS232 signalling unless I have to due to choices made by others. RS232 isn't that robust in the end, so either logic level for simplicity and least part count, or some differential solution like RS422/485 or CAN. The latter can be had at the same complexity (a transceiver chip) as RS232.

[DiTBho]

My Japanese laptop also adds a Canbus @ 1Mbps port with a funny 4 pins connector.
My Japanese graphic calculator has a 3 wires serial-ling, which is actually a true LVTTL serial line @ 115200bps.

Will Canbus replace RS232? Who knows 

[NiHaoMike]

She's been around for, let's see, 2015 at least, don't remember how many years before that?  Her appearance is unconventional, I suppose you might say, but she's got lots of electronics/programming/hacker/maker experience.

I expected her to know what it is, but not to have a device that used it. Most modern devices that have a serial port for configuration use a logic level UART connector or integrate a USB UART chip.

Will Canbus replace RS232? Who knows 

Only if CAN interfaces become as common on microcontrollers as UARTs are now. I would say there's a better chance of USB OTG replacing UART, but UART has the simplicity that others don't.

Other potential alternatives would be I2C and SPI. I2C is a bit more complex with addressing while SPI is the fastest but also the highest pin count. What used to be an advantage over UART was no need for a precise clock, but many microcontrollers nowadays have internal oscillators good enough for UARTs.

[Siwastaja]

Will Canbus replace RS232? Who knows 

For general purpose maintenance/debug/low cost device port - no. CAN stays where it is useful, and those maintenance ports partially stay in RS232, partially transfer to logic level serial, and partially transfer to more complex alternatives such as Ethernet, bluetooth, other wireless, or custom ports.

[DiTBho]

Only if CAN interfaces become as common on microcontrollers as UARTs are now. I would say there's a better chance of USB OTG replacing UART, but UART has the simplicity that others don't.

There are a lot of Freescale MPUs that come with an embedded CAN, also there are a some good and cheap SPI-CAN chip. So, it seems possible.

Other potential alternatives would be I2C and SPI

Both my Japanese PDA and laptop come with I2c and SPI. The laptop also has CAN, "RS232-4W"(1), I2C and SPI; however, I2C and SPI are only used internally(2), there is a little connector under the plastic, you can somehow access it, but you cannot connect a cable longer than 20cm, and that's the point! CAN and RS232 can be used with long cables! Even longer than 1m.



(1) "RS232-4W" means { 3.3V, TX, RX, GND }, it's sometimes routed to a RJ12/4pin (usually with routers)
(2) there are several SPI channels, one connects the boot flash, that contains u-boot.
I2C and I2S are used to connect the touchscreen chip, and the sound chip, but there is a fourth channel not used, routed to a small connector.

[DiTBho]

For general purpose maintenance/debug/low cost device port

With Linux I haven't yet understood if it's classified as "network" device, or "char" device 

[PKTKS]

Have a half dozen  devices still using RS232 and COM ports

Got some COB type dongles and still wondering if I will buy one of these multi serial PCI COM port adapters to have full RS232 still ready...

Either not having the RS232 signaling levels the protocol is still required by some gizmos..

Paul

[rfclown]

I'm working on new designs for military gear and RS232 is still required.

[Siwastaja]

For general purpose maintenance/debug/low cost device port

With Linux I haven't yet understood if it's classified as "network" device, or "char" device 

CAN is pretty specific and can't easily replace "byte stream" devices. CAN is absolutely great for certain tasks which naturally fit with the CAN's ideology - publish structured data with identifiers, no "command"-"reply" interactions - but forcing something like a byte stream through CAN is horrible use of CAN.

CAN can not (  ) be used as a byte stream, because a hardware-delimited CAN packet is a structured piece of data with specific fields with specific meanings, all important. All CAN implementations I have seen, including socketcan, Kvaser API and PCAN API (it sucks not to have unified API on Windows), implement such structured data; for example, socketcan exposes a CAN packet as a C struct.

In linux, as a network device, you are still limited to reading a CAN packet in a byte array using read(), but AFAIK you can be sure to get a full packet (sizeof (struct can_frame)) at once, i.e., short count should not happen. Typical pattern is

Code: [Select]

struct can_frame frame;
nbytes = read(cansoc, &frame, sizeof(struct can_frame));
if(nbytes != sizeof(struct can_frame))
{
    // unsupported failure mode, never seen this happen,
    // maybe someone can confirm if this is _guaranteed_ to never happen?
}


Worst part of CAN is that it is ungooglable due to the stupid name choice. What next, how about "is" protocol? "l" would be pretty good as well (that's a lower case L in case you didn't already notice, just for confusion.)

[peter-h]

RS232, 422, 485 will live on, because

- the chip costs peanuts (MAX232 sort of thing)
- the software overhead is ~zero (CAN USB ETH are all massive, and complicated for customers to use except in very narrow cases)
- anybody can use it, straight away

Interfacing serial comms, and making USB-serial converters, etc, is my day job and has been for 30 years. Much less demand these days, for sure, but that's because things tend to get integrated more, and as companies lose people with real skills (retirement) they install turnkey systems which naturally use closed architectures (for customer entrapment).

How much surgery has that girl had done??

[NiHaoMike]

One thing I find lacking with both USB to serial adapters as well as "proper" UARTs on PCs is the lack of standardized support for 9 bit mode, something most microcontrollers support. That provides a good way to implement out of band framing for data values that are a multiple of 8 bits, for example binary data.

Both my Japanese PDA and laptop come with I2c and SPI. The laptop also has CAN, "RS232-4W"(1), I2C and SPI; however, I2C and SPI are only used internally(2), there is a little connector under the plastic, you can somehow access it, but you cannot connect a cable longer than 20cm, and that's the point! CAN and RS232 can be used with long cables! Even longer than 1m.

Almost every PC has I2C exposed on an external port, that's part of VGA and DVI/HDMI. It is, however, rather low bitrate. Displayport switched to its own serial protocol to work better with stuff like touchscreens.

Worst part of CAN is that it is ungooglable due to the stupid name choice. What next, how about "is" protocol? "l" would be pretty good as well (that's a lower case L in case you didn't already notice, just for confusion.)

Searching "can bus" seems to work at least on Duck Duck Go. It has been a long time since I last used Google for web searching, I suppose if it's even more garbage than it was back then, it's time to switch to something else.

How much surgery has that girl had done??

She identifies as a cyborg ("part robot") so quite a bit. Funny thing is, back when I was in elementary school, I had a hard time finding friends (because I read so much about science and technology) so I wished for a robot to be my friend, a wish that kind of came true. I think her unusual appearance is to try to set herself apart from other models in technology like Xyla Foxlin and Sarah Petkus.

[nctnico]

RS232, 422, 485 will live on, because

- the chip costs peanuts (MAX232 sort of thing)
- the software overhead is ~zero (CAN USB ETH are all massive, and complicated for customers to use except in very narrow cases)
- anybody can use it, straight away

You forget reliability. Last year I did a relatively large project which consists of several sub-units. The communication between them uses RS232. The unit itself has a USB port which identifies/works as a serial port.

How much surgery has that girl had done??

Way too much if you ask me   

[james_s]

Way too much if you ask me   

I have a hard time taking someone seriously that tries that hard to get attention, it's a gimmick IMO, it reeks of desperation and it's distracting. She looks like she'd be working in an adult entertainment venue, not an engineering lab.

[NiHaoMike]

You forget reliability. Last year I did a relatively large project which consists of several sub-units. The communication between them uses RS232. The unit itself has a USB port which identifies/works as a serial port.

Actual RS-232 or just a logic level UART? Those terms are often used interchangeably when RS-232 refers to the +-12V signal levels that operate with a UART at the core.

On reliability, it's not really true of half duplex RS-485. Most UARTs don't implement CSMA/CD in hardware so it's up to you to do it in software. It's especially problematic if the system doesn't have real time capability. (Some better USB to RS-485 adapters use a microcontroller instead of a standard USB UART for that reason.)

She looks like she'd be working in an adult entertainment venue, not an engineering lab.

I don't think she'll be a particularly great dancer with such a high center of gravity.

[nctnico]

You forget reliability. Last year I did a relatively large project which consists of several sub-units. The communication between them uses RS232. The unit itself has a USB port which identifies/works as a serial port.

Actual RS-232 or just a logic level UART? Those terms are often used interchangeably when RS-232 refers to the +-12V signal levels that operate with a UART at the core.

I mean the +/-12V levels. There shouldn't be much confusion about that though 

[peter-h]

Most products which are "boxed" and with RS232, have a swing of at least -5V to +5V. You can get that with a MAX3232, which runs from +3.3V.

There may be some which swing -3.3V to +3.3V but I haven't seen that.

The 0 to +3.3V or 0 to +5V cases tend to be board-level products e.g. development boards.

Indeed, RS232 is "reliable" because there is no chance of DHCP not working or any of the thousand other things which break the more advanced methods. Same for RS422 or RS485 which are equally cheap to implement.

[Raj]

I highly doubt that it's the S£xy cyborg that's the brain behind her videos. People have speculated that it's her engineer husband.
I just want someone unbiased, to meet her in person and test her knowledge out.

Kasyan TV used to have a male voiceover, until it became popular. Now a female voices the channels video.


Side note:
While typing this, I realized that windows has F-ed up my keyboard settings and when I type "#", or shift 3, it prints "£" symbol.

[NiHaoMike]

I highly doubt that it's the S£xy cyborg that's the brain behind her videos. People have speculated that it's her engineer husband.

There is no husband, she's a lesbian. Also, a lot of smart Asians are also very good looking. (Look up Kitty Yeung and Xyla Foxlin for more examples in engineering.)

[DiTBho]

Found a couple of sonar sensors. They offer RS422 as communication link.
Nice. I can wire a 5m cable without any problem 

[PKTKS]

Most products which are "boxed" and with RS232, have a swing of at least -5V to +5V. You can get that with a MAX3232, which runs from +3.3V.

There may be some which swing -3.3V to +3.3V but I haven't seen that.

The 0 to +3.3V or 0 to +5V cases tend to be board-level products e.g. development boards.

Indeed, RS232 is "reliable" because there is no chance of DHCP not working or any of the thousand other things which break the more advanced methods. Same for RS422 or RS485 which are equally cheap to implement.

Industry grade products are RS232 and GPIB ready ..
and LXI  counts as a feature...

No serious industry device lacks RS232 as of  today..
https://www.kikusui.co.jp/en/product/selection.php?Category=DC%20Power%20Supplies

It may vanish someday..  but not now..

Paul

[nctnico]

You won't find RS232 on most modern test gear. USB and ethernet are standard nowadays (where USB typically mimics a serial port even if it is called USB TMC).

[PKTKS]

You won't find RS232 on most modern test gear. USB and ethernet are standard nowadays (where USB typically mimics a serial port even if it is called USB TMC).

Well I have placed a proper URL reference for that reason...

Depending on the "level" we a are talking... ..
serious industry grade devices can not suppress RS232 (yet)

and.. I just REFUSE to GROUND my bench test gear with these USB dongles wide spread among everything...


I know WINTEL invested insane amounts of money to have the property of USB and HDMI dongles.. and chips and specs..  and they will not let go to the bitter end..

But is just pathetic that dongle thing.

I have now a bunch of  DONGLE for THE DONGLES and new DONGLE version.

They are piling up against each other..

nahhh I will not ground my bench devices that way...   

Paul

[nctnico]

RS232 is ground referenced just like USB so that doesn't make any difference. RS232 is also relatively slow compared to USB.

[PKTKS]

RS232 is ground referenced just like USB so that doesn't make any difference. RS232 is also relatively slow compared to USB.

They are quite different...

RS232 has no HUB and when made for "industry grade" device attach...
they are safer.

They were already made for that...  industry COM ports.

Not USB.
USB a gadget gizmo device.

Paul

[DiTBho]

The first time I used a serial, the chip was referenced as "ACIA" and there was an external baudrate generator because the chip was unable to generate its own baud clock. The maximal value was 9600bps, it was the time of BBS and early internet through a serial dial-up modem coupled with a phone, but the common bit per second was 1200, sometimes 2400.

In the 1990s, 9600 bps was considered "turbo"

Years later, ADSL-modems were able to go up to 115200bps. USRobotics was one of the first modem able to reach 1Mbps, even if the ADSL part of the modem was unable to follow the signal on the phone line with a decent fail rate, and what's the sense of going faster if more than half of the bits are wrong?!?

[DiTBho]

gadget

don't mention it ... USB3-things are really shocking with certain SoC chips.

With H3 SoC (2016) you have "combined HDCs", with three controllers OHCI, EHCI, XHCI all multiplexed to the same physical pins, so you also have to program the PHY (and this also implies a bus to communicate with the PHY).

OHCI does not even work good, so why is there?!? And with EHCI and XHCI you also have to specify if the PHY and the HDC are set to operate as

• host
• device
• OTG (<------ this needs an extra pin in the PHY to select{host, device} on demand)
• gadget (<------ this USB3's stuff, and it's used as a wild way to encapsulate Ethernet over usb)

While my old Ath5 SoC (2005) has a simpler USB HDC that only operates as host, and it only supports EHCI, and the PHY is directly connected to the HDC.

[nctnico]

RS232 is ground referenced just like USB so that doesn't make any difference. RS232 is also relatively slow compared to USB.

They are quite different...

RS232 has no HUB and when made for "industry grade" device attach...
they are safer.

Doesn't matter. Besides that equipment should be grounded through the mains ground or an external ground strap bolted onto the device. Not through a detachable interface whether it is RS232 or USB.

[PKTKS]

I do not ground my instruments (EARTH ground).

ALL MY BENCH IS ISOLATED USING DEDICATED TRAFOS.

That includes my computer bench (workstations and NAS)

One thing is connect 2 devices  - PC and instrument - via RS232.

Another thing .. is connecting a plethora of small USB gizmos and HUBs..
and each using a different set of interfaces and power requirements..

Having USB on my bench is a nightmare.. 
I have crafted an ISOLATED HUB just to host these most important ones...

Still I am not ok when putting them.. even being ISOLATED (isolated powered HUB)
They put a COMMON GROUND among devices..

Hard to predict safely

Paul

[DiTBho]

The perfect isolated UART is ... IrDA, or the optical link used in some multimeters.

[PKTKS]

The perfect isolated UART is ... IrDA, or the optical link used in some multimeters.

Fro DMMs is ok  when they have both usually I got them both

For my Uni_Ts :
UNIT-UT-D02 RS232
UNIT-UT-D04 USB


But USB SCOPES gizmos and func.gens and other stuff ...
hardly will have opto isolated ready cables..

My BENCH IS FULLY ISOLATED SETUP - nothing connects EARTH.

EARTH connection was banned decades ago

DMMs are floating devices.. but grounding USB gizmos adhoc is a hazard

Paul

[DiTBho]

and what about Ethernet connection with isolated transformers?
RIGOL sells DSO and function generators with Ethernet. Not expensive, and it offers good bandwidth.