to start from scratch

A

Thread Starter

arun

I am working on a project and it involves a communication link. there is a master and there are 4-5 slaves to be controlled. the slaves are motor drives. since the drives (slaves) themselves are intelligent the master just needs to start and stop the slaves to simply share the load between the slaves. the master also needs to have a Log of the details of the slaves (running time etc..)that has to be periodically shifted to a computer. the physical layer has to be a rs 485 interface.

Can some one please suggest me if I should use the modbus protocol for a simple sequence like this?? and if so where should i start? because I simply am starting from the scratch and am practically at point ZERO now.

thanks and regards
Arun
 
H

H.-J. Oertel

When you are starting from scratch, why restrict communication to RS485 physical layer? Decentralized intelligent drives are ideally controlled with CAN (CANopen or DeviceNet as higher layer) networks.
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with best regards / mit freundlichen Grüßen

Heinz-Jürgen Oertel
+==================================================================| Heinz-Jürgen Oertel port GmbH http://www.port.de
 
F

Friedrich Haase

Moin arun,
moin all,

CAN uses the physical layer somewhat different from most other RS485 field busses. You will need special CAN controller chips or CAN controller boards for every node.

Why not keep it simple - use good old MODBUS?

Best regards
Friedrich Haase

Ing.-Büro Dr. Friedrich Haase
Consulting - Automatisierungstechnik
email [email protected]
WEB http://www.61131.com
 
H

Heinz-Juergen Oertel

> CAN uses the physical layer somewhat different from most other RS485
> field busses. <

Correct, because CAN is not RS485, the physical layer is defined in ISO-11898-1
http://www.can-cia.org/can/
http://www.can-wiki.info/CanFaq

> You will need special CAN controller chips or CAN
> controller boards for every node. <

You need of course an transceiver chip, but where is the difference anyway if is beginning from scratch, he can choose. You can find many microcontrollers with integrated CAN, there si in the most cases no need for 'special CAN controller chips' And I suggested CAN mainly not because of the physical layer, but because of the advantages the data link layer provides for the software engineer. It dramatically simplifies software for distributed control.
Thats what CAN was intended for.

with best regards / mit freundlichen Grüßen

Heinz-Jürgen Oertel
http://www.port.de
 
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