we now have a control board with a rs485 port, and now we want to implement the modbus/RTU protocol. should we add any hardware such as IC, timer in our board? or we just can implement modbus/RTU by programming?

 

Add a hardware such as ADAM-4520 that is change signal from RS232 to RS485.

 

my hardware have a rs485 port already, which a microcontroller connect to rs485 directly, but I don't know should I add any extra hardware to meet the modbus/rtu requirement such as a 'modbus controller' or timer etc.

 

Hardware wise you need:
- a UART

- RS485 line drivers

- The ability to switch on and off the RS485 transmitter by software or automatically by hardware. Very important.

- A time base for time-out control and silence interval control. This time base can be provided by a timer interrupt or the operating system (if you are using one).

If you are interested in a stack implementation you can have a look
at: "http://www.focus-sw.com/fieldtalk.html":http://www.focus-sw.com/fieldtalk.html

Henrik Maier::
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FOCUS Software Engineering
Brisbane, Australia
http://www.focus-sw.com
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