[ARM] How to handle if more than two slaves sends their data to master at the same time?

[santukatke]

Greetings,

I am trying to communicate four ARM controllers by using modbus protocol.Everything is working properly but when two or more slaves sends their data to the master then only one slave's data is receiving at master.

Thanx in advance.

 

[paulfjujo]

 when two or more slaves sends their data to the master

so, they are not realy slaves !
A slave must give a response WHEN the master requier some datas.
The master send a modbus request wich contains a slave adresse, and wait the response within a timeout delay..
except when send a broadcast adress ..for all slaves.

 

[hobbyckts]

You need to address the slave devices one by one and then need to read the data

 

[Gorgon]

The MODBUS protocol normally has only 1 master, and the rest is slaves. The master asks each slave in sequence, and the slave asked, reply with whatever status or info asked for.

The master ask every slave active in the net, in an everlasting sequence.

The slave will always answer an enquiry!

 

[santukatke]

Thanks for reply,

These posts are really useful for me.