need help for parallel connection of rs485

Status
Not open for further replies.
D

dsanthosh67

Member level 4
Joined
Jul 25, 2014
Messages
69
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,296
Location
INDIA
Activity points
1,886
Hi all,

Actually i am working with ADM2587E rs485 communication its works fine with single master and slave,but i am not able to connect multiple slave with single master.kindly help me for the connection,when i workout with this a junk value will received at the time of transmit a data....

Regards,
Santhoshkumar
 

RS-485 communication depends on only one peer activating Tx enable (signal DE) at a time. How is this achieved in your slave design?

It may be necessary to have pull-up/pull-down resistors for a proper bus idle state ("mark") when it's not driven by any side.
 

Totally i worked with 3 boards connected parallel,By default Tx enable pin(DE) is High and the Rx enable pin(RE) is low in all the boards.Then what's the solution...
 

I guess from your description that you are using the full duplex configuration as described in figure 42 of the ADM2587E datasheet (otherwise a single slave would work neither with permanently enabled transceivers).

The solution is to enable only one slave transmitter at a time and leave it disabled by default. Some UARTs are providing a transmit enable signal in hardware automatically (may need to be inverted). Otherwise the transmitter can be controlled by software or a hardware timer.
 

ya you are right when i work with single master and slave it works fine,more then one slave only the problem arise, i am trying to solve the issue by your way, Thanks for reply..
 

Status
Not open for further replies.

Similar threads

Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…