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RS485/RS422/RS232 vs. ModBus/CanBus/LinBus

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can bus vs rs485

I just discovered RS485/RS422 and might do some design with those. However, with all the new Buses around, is it a smart move?

Is the popularity of RS485/RS422 on the way down? Any marketing information on the number of devices with such interface?



ASIC
 

rs232 vs rs485

I think that the progressively cheaper hardware allows us to use more sophisticated communications with a low cost.
Sometimes the environment imposes the standard.
After a development for automotive I use CANbus in industrial applications.
 

can vs rs485

RS422/485 is almost non-existant. Very few devices use it and the ones that do are older legacy systems. Most developers are opting for ethernet now.

jelydonut
 

modbus vs rs232

to jelydonut:


I can see many devices from companies like as advatech that support RS485,but they do not provide them with CAN,
 

rs232 vs can

there are no limit to rs485 speed , Maxim Max485 work at 2.5Mbps, my opinion is that Canbus is the effect of globalization, the electric layer is similar to rs485, only difference is the protocol. in rs485 i make multimaster without problem, i can control conflict on the bus,I'm free to implement my protocol in anytype of microcontroller and I'm free to make application in any PC language
jelydonut said the few company use it, but is false, the industrial world is full of the rs485 devices.
The CanBus ig Germany concept, and I speak for experience (my wife is germany), the germany's mind can make complicate the simple!!!
 

Re: can vs rs485

jelydonut said:
RS422/485 is almost non-existant. Very few devices use it and the ones that do are older legacy systems. Most developers are opting for ethernet now.

jelydonut
Click to expand...


It is not like that RS232, RS422, RS 485 is still being used in embedded system/products or microcontroller based system. It is also used for downloading the software as a media to download the software.
but yes still ethernet is prefferd one in higher end application and system. and market is trying to replace it. For lower end/ simple non complicated system it is still being preffered to use RS232 or RS485.
 

Re: modbus vs rs232

7rots51 said:
to jelydonut:


I can see many devices from companies like as advatech that support RS485,but they do not provide them with CAN,
Click to expand...

jelydonut is exactly right.

Originally, data transmission on the plant floor was done by proprietary twisted pair serial communications protocols (like RS-232 and RS-485) which were deterministic by nature, since they were half-duplex. There was a defined amount of time to wait for any response after sending any message from the master. The timing was very predictable (hence deterministic) but it was very slow.

Industrial data network was Modbuse which hencing the name MODiconBUS. Modbus, being half-duplex, is highly deterministic, but being serial, is quite slow, with data transmission rates as rates as slow as 300 baud (typically 2.4Kbaud).

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Good Luck!
 

Distance affects pF/ft of cable as well as twists/ft and diameter. Std cable as I recall is 12~15pF/ft and low loss cable is 6pF/ft.
There are other factors but RS485 is still used in remote Lightning controllers in both half (HDX) and full duplex (FDX).
RS-485 can be used in 2 (HDX) or 4(FDX) wire modes and protected up to +-15kV and some up to 16Mbps (FDX) or 30Mbps (HDX)

Screen shot 2012-07-29 at 6.15.29 AM.pngScreen shot 2012-07-29 at 6.27.43 AM.png
Canbus has some minor improvements for multipoint speed connections.. to improve cost and performance. at signal layer. but uses CSMA/BA for contention priority control and 0~8bytes words and can have error control at chip level.
Screen shot 2012-07-29 at 6.21.06 AM.png Screen shot 2012-07-29 at 6.22.25 AM.png
 
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