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RS-485 Addressing

dtuckerdtucker Posts: 7
in AMX Technical Discussion
How do you address an individual device on an RS-485 bus? By default, data is broadcast, but I need to target a particular device.

Any help would be greatly appreciated.

Thank,

David

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    Joe HebertJoe Hebert Posts: 2,159
    dtucker wrote: »
    How do you address an individual device on an RS-485 bus? By default, data is broadcast, but I need to target a particular device.
    What device are you referring to?
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    Joe HebertJoe Hebert Posts: 2,159
    As a follow up, there is no one size fits all answer.
    The address will be embedded in the data packet.
    Where it?s placed and how the packet is formatted depends on the protocol of the device in question.
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    veraviewveraview Posts: 44
    It will all depend on the string that you have to send to the device. For example, if there are three devices on the bus you will have to know how to address it using that particular manufacturers' protocol:

    Turn display number one on:
    SEND_STRING dvDisplay485, 'display1 on'

    Turn display number two on:
    SEND_STRING dvDisplay485, 'display2 on'

    Notice that in each example, you are sending a command to the same device, dvDisplay485, but it is up to the individual display on the bus to listen for a command sent directly to it.
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    dtuckerdtucker Posts: 7
    I see. I was under the impression that the RS-485 protocol itself provided the mechanism for addressing. I guess it just provides the mechanism for signal distribution (daisy chaining, basically) so that higher level protocols can utilize addressing.

    I know what to do, now. Thanks again.
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