RS232 vs USB and Firewire

[yasser_shoukry]

rs-232 vs firewire

I want to ask a simple question :

Is there certain applications the new serial communication standards USB and Firewire can't replace the old RS232 standard ???

 

[Davood Amerion]

yes,
there are hard limitation on cable lenght on USB, and firewire,
as i know maximum cable lenght for USB is 1.5-2 meter
whereas maximum cable lenght for RS232 (with maximum baud rate) is 15 meter.
if its baud rate is low it can be used for upto 100 meter.
RS232, still, used in industires and telecommunications.

 

[xxargs]

I want to ask a simple question :

Is there certain applications the new serial communication standards USB and Firewire can't replace the old RS232 standard ???

Yes


Electrical length i limited in USB and firewire, but also big problem for USB is master and slave relation - slave unit cannot send message or take over master role. and master need poll every slave all time to recive slaves status.

IEE1394/firewire have better thinking for future, and can use TP-cable and optical fiber in future for long way connect.

but none of them can with simple rewiring change role from DCE to DTE or connect host to host, slave to slave etc. for technical guys very importent flexibility for making equipment working together.


In practic working USB/RS232 adapters very bad if you want near realtime communication over RS232 typical fast few bytes question-answer-question-answer-protocol.

Every byte send or recive from (often old) application have uncalculated delay if you try sending via USB/RS232 converter and in many time not working or slowing application to unusable state. but working fine if you using 'old' UART in laptop or RS232/UART via PCMCIA.

for example talking Garmin GPS 12 XL in garmin protocol and want 10 GPS-coordinate per second (in 9600 Baud), its possible with using old UART-RS232 but impossible via USB/RS232 converters depend of extra delays for every transaction in windows/USB-enviroment give only recive 5 coordinats per sec...

Is now hard to find new laptop with working RS232-connectora and is bad situation for technical guys and people needs manage old (and uniq) industrial equipment via RS232 depend of USB/RS232 inteface not working all time or struggling badly witht old software in PC and firmware not possible to adjust communications parameters...

 

[eltonjohn]

Flywire and Usb are more complex buses than rs232 .They are multi slave devices ! So the specs are much diferent I will consider also Ethernet as a comunication posibility if the distance is a problem .There is a lot of cheap resources for it!