Forums

RS232/485 impromptu survey.

Started by Not Really Me September 19, 2005
How popular is that old standby async/sync serial data in new embedded 
designs?
I know there are lots of other technologies coming into play from ethernet 
to wireless, USB, etc., but what percentage of your new designs are using 
RS232 or RS485?

I still see it on almost every project.  If not as an intended interface 
then at least for debugging.

Your comments are appreciated.

Scott
Validated Software 


Not Really Me wrote:
> How popular is that old standby async/sync serial data in new embedded > designs? > I know there are lots of other technologies coming into play from ethernet > to wireless, USB, etc., but what percentage of your new designs are using > RS232 or RS485? > > I still see it on almost every project. If not as an intended interface > then at least for debugging. > > Your comments are appreciated. > > Scott > Validated Software > >
Async serial is never going away. The simplicity of it vs. USB or ethernet is not even a topic worth discussing - too obvious. Many, many micros will have only async on board for the foreseeable future. As for RS232, it has disappeared from most computers - but USB to async adapters are around. This might be a good time to ask which ones work and which ones don't. Believe it or not, there are many USB to async adapters that just don't work!
Not Really Me wrote:
> How popular is that old standby async/sync serial data in new embedded > designs? > I know there are lots of other technologies coming into play from ethernet > to wireless, USB, etc., but what percentage of your new designs are using > RS232 or RS485? > > I still see it on almost every project. If not as an intended interface > then at least for debugging. > > Your comments are appreciated. > > Scott > Validated Software > >
The group I work with has done about 8 controllers over the last 3 years. These all include RS422 async single and/or multi-drop. None of these controllers are sold individually - they are part of a larger machine. The protocols are all passing strings around. These async interfaces are the primary interfaces to these controllers. I can't imagine spending valuable time futzing with USB or some such modern scheme, when there's work to be done.
Not Really Me wrote:
> How popular is that old standby async/sync serial data in new embedded > designs? > I know there are lots of other technologies coming into play from ethernet > to wireless, USB, etc., but what percentage of your new designs are using > RS232 or RS485? > > I still see it on almost every project. If not as an intended interface > then at least for debugging. > > Your comments are appreciated.
When the datarate of my device is sufficiently low, I integrate a serial port, usually selectable between RS232 and RS422. These USB drivers are a pain. Who is going to promise me that in 20 years, any USB device is still functional ? They usually rely on windows drivers and MS comes up with a new concept every couple years. With Serial, and the hardware level translator in place I can be sure that the device is interfaceable in another 20 years. Thanks to TexasInstruments, I found an RS485 driver that does 25MBit over 160m, and another set that does 3MBit over 500m. So even with a medium datarate, my devices can have a serial connection. Yes, a serial to USB is proposed external to the device. Rene -- Ing.Buero R.Tschaggelar - http://www.ibrtses.com & commercial newsgroups - http://www.talkto.net
"Rene Tschaggelar" <none@none.net> wrote in message 
news:432efee3$0$1161$5402220f@news.sunrise.ch...
> Not Really Me wrote: >> How popular is that old standby async/sync serial data in new embedded >> designs? >> I know there are lots of other technologies coming into play from >> ethernet to wireless, USB, etc., but what percentage of your new designs >> are using RS232 or RS485? >> >> I still see it on almost every project. If not as an intended interface >> then at least for debugging. >> >> Your comments are appreciated. > > When the datarate of my device is sufficiently low, I integrate a serial > port, usually selectable between RS232 and RS422. > > These USB drivers are a pain. Who is going to promise me > that in 20 years, any USB device is still functional ? > They usually rely on windows drivers and MS comes up > with a new concept every couple years. With Serial, and the > hardware level translator in place I can be sure that > the device is interfaceable in another 20 years. > > Thanks to TexasInstruments, I found an RS485 driver that does 25MBit over > 160m, and another set that does 3MBit over 500m. So even with a medium > datarate, my devices can have a serial connection. > > Yes, a serial to USB is proposed external to the device. > > Rene > -- > Ing.Buero R.Tschaggelar - http://www.ibrtses.com > & commercial newsgroups - http://www.talkto.net
Thanks for the comments, please identify the TI driver. scott
Not Really Me wrote:
> How popular is that old standby serial data in new embedded designs?
Very popular here! We sell industrial electronic modules that often wind up connected to equipment with serial ports. Using a laptop with a USB port might be nice for doing the setup or for loading a program, but only a small part of it's life is spent doing that. And cheap converters are available for that. -- Gary Peek mailto:mylastname@mycompanyname.com Industrologic, Inc. http://www.industrologic.com Phone: (636) 723-4000 Fax: (636) 724-2288

Not Really Me wrote:
> How popular is that old standby async/sync serial data in new embedded > designs? > I know there are lots of other technologies coming into play from ethernet > to wireless, USB, etc., but what percentage of your new designs are using > RS232 or RS485? > > I still see it on almost every project. If not as an intended interface > then at least for debugging. > > Your comments are appreciated.
Let me put it this way: Sales started asking about USB versions of our software. We use serial cables and RS-232, but some newer laptops don't have serial ports. We increased the available ports on the software from 1-4 to 1-8 and included a 3rd-party USB converter cable in the box. Any product we have that talks to another device uses RS-232. ANY product. -- Magnus McElroy Electrical Engineer (EIT) HABIT Research (250) 381-9425
On Mon, 19 Sep 2005 20:08:31 +0200, Rene Tschaggelar <none@none.net>
wrote:

>Thanks to TexasInstruments, I found an RS485 driver that does 25MBit >over 160m, and another set that does 3MBit over 500m. So even with a >medium datarate, my devices can have a serial connection.
Are these distances and speeds for point to point connections only or are multidrop connections also possible ? Profibus-DP (which is essentially RS-485 with asynch characters) is quite picky at 12 Mbit/s at 100 m. Small series inductances are needed in the main line at each DB-9 T-connector to compensate for the branch capacitance, even if the transceiver is just a few millimeters from the connector in each node. Paul
On Mon, 19 Sep 2005 11:47:16 -0600, "Not Really Me"
<scott@exoXYZtech.com> wrote:

>How popular is that old standby async/sync serial data in new embedded >designs? >I know there are lots of other technologies coming into play from ethernet >to wireless, USB, etc., but what percentage of your new designs are using >RS232 or RS485? > >I still see it on almost every project. If not as an intended interface >then at least for debugging. > >Your comments are appreciated.
In addition to others' comments, you can bit-bang an RS-232 interface on any microcontroller (I couldn't imagine bit-banging USB even on a processor fast enough to do it), no serial port needed (or no EXTRA one needed if the one(s) you have are dedicated to something else). If you're doing on-board interprocessor communication, you don't even need the voltage/level translation (i.e. no MAX232 chip), though most chips have some sync ports that would do better for on-board comm. Even if it's running on a 32.768kHz clock crystal and a watch battery, you can do something like 300 baud in software (I doubt you could power a USB interface with a watch battery, and certainly not for very long). Even if the controller doesn't have a timer, you can do ugly timing loops and at least transmit easily. Receiving isn't as easy as transmitting, but with a timer interrupt you can do full duplex with no problem, up to some max baud rate depending on processor throughput and clock frequency. The next lower-level interface to the real world would be a pushbuton swich and an LED, using the same port hardware as basic no-flow-control RS232 (one output bit, one input bit), but the data rate for this is a lot slower, and a lot of people haven't even heard of Morse code...
>Scott >Validated Software
Ben Bradley wrote:
> In addition to others' comments, you can bit-bang an RS-232 > interface on any microcontroller (I couldn't imagine bit-banging USB > even on a processor fast enough to do it)...
Bit-banged USB on an AVR: http://www.avrfreaks.net/index.php?module=FreaksTools&func=viewItem&item_id=459