Help need in interfacing RS485.........

[sanddune008]

Hi All,

How to interface PIC to RS485? Is it possible to connect the MAX RS485 to the UART.....if so how do i proceed with? Do i need to introduce some protocols. As i am new to this.

Basically i am trying to send command bytes over distances greater than 100mtrs with speed not an issue. With multiple end devices connect to it receives the command at the same time.

Any other solution is a welcome.......

Thanks in advance

 

[blueroomelectronics]

RS422 is very east to use for long distance point to point. It's full duplex so just hook tx to one pair and rx to another pair.

 

[sanddune008]

Thanks Bill for your time

RS422 is very east to use for long distance point to point.

I am connecting multiple slaves and ensure all the slaves receive the command.
basically sending the command in one direction/

It's full duplex so just hook tx to one pair and rx to another pair.

So all i need to do is hook the Tx and Rx of the uart to the MAX422.


Thanks in advance

 

[blueroomelectronics]

RS422 can support 10 listeners. RS485 usually 32 or more. Do the remotes talk back or only receive?

 

[sanddune008]

RS422 can support 10 listeners. RS485 usually 32 or more. Do the remotes talk back or only receive?

remotes(slaves) will only receive.

Basically i am designing a hub with i/p's(max of 4 inputs) from actuators and slaves connected to the hub(output). When an acutator input is received process it and sent a common command to all the salves connected to the ouput....based on the command each slave will do the necessary.

how do i interface the RS485 to the PIC UART?

Is there any other solution?

Thank in advance

 

[sanddune008]

Quote:
Originally Posted by blueroomelectronics View Post
RS422 can support 10 listeners. RS485 usually 32 or more. Do the remotes talk back or only receive?
remotes(slaves) will only receive.

Basically i am designing a hub with i/p's(max of 4 inputs) from actuators and slaves connected to the hub(output). When an acutator input is received process it and sent a common command to all the salves connected to the ouput....based on the command each slave will do the necessary.

how do i interface the RS485 to the PIC UART?

Is there any other solution?

Thank in advance

 

[blueroomelectronics]

Since it's unidirectional you can simply use a RS485 IC and set its direction to transmit on the master and receive on all the slaves.

 

[sanddune008]

Hi,

yes its unidirectional.

Somehow the UART interface to MAX485 IC doesn't seem to work.

Master sends hello which is to be received by the slave. I see lot of noise between the nodes.

Attached is my schematics....

Can some one please verify my schematics.

Thanks in advance

 

[sanddune008]

Meanwhile i started of with testing the ckt with 2 nodes and the Rx enable and
Tx enable hardwired.

I am using a CAT5 cable(twisted pair of white and orange) of length 2feet.I guess its characteristic impendence to be 100ohm.

can someone please verify my schematics.............

Thanks in advance

 

[sanddune008]

Meanwhile i started of with testing the ckt with 2 nodes and the Rx enable and
Tx enable hardwired.

I am using a CAT5 cable(twisted pair of white and orange) of length 2feet.I guess its characteristic impendence to be 100ohm.

can someone please verify my schematics.............

Thanks in advance

 

[blueroomelectronics]

Connect DE & RE together on each MAX485.

 

[sanddune008]

Thanks
Connected DE and RE pins together....Issue doesn't seem to resolve...

LCD displays junk data....I see signal at RO pin is irregular in shape.

What could be the probable reason for this?

Thanks