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Rs485

e-newbiee-newbie Posts: 3
edited 2011-05-24 09:14 in BASIC Stamp
Hi guys,

I am a beginner with Basic stamp and I'm trying to retrieve data from a device using RS485.

On the front panel of the device there are three clamps (RX, TX and RTS) indicating the RS485 port. I need to know how to connect these terminals to the BS2.

I suppose that RX and TX could be connected to, for example P0 and P1, and RTS as ground to Vss.
But I'm not sure. Do I need some resistors for P0 and P1 ?
Please, could you help me with an electronics diagram ?

I wanto to go further the basic examples but I need some guidance. Sorry for my bad english.

Thanks in advance

Regards

Paul

Comments

  • schillschill Posts: 741
    edited 2011-05-24 07:33
    I can't offer too much help, but it does not sound like the device is using RS485. RX, TX, and RTS sound more like RS232 or TTL-level serial. Do you have any more information about the device you want to connect to?
  • e-newbiee-newbie Posts: 3
    edited 2011-05-24 07:44
    There is the label "RS485" above the clamps.

    The device is a solar inverter and the generated data are logs about the produced power. Here, http://it.power-one.com/sites/power-one.com/files/pvi-10.0-12.5-outd-en_13042010.pdf, you can find more info about the inverter.

    Thanks
  • Mike GreenMike Green Posts: 23,101
    edited 2011-05-24 07:51
    The link you provided gives no information about the "RS485" connections. You will have to do some research to find a manual or other more detailed information. The labels ("RX", "TX", and "RTS") make no sense in the context of RS485 and, if you don't know what you're doing, you can damage part of the inverter or your Stamp or whatever you're using for interfacing.
  • e-newbiee-newbie Posts: 3
    edited 2011-05-24 08:16
    You can see an image of the clamps on the image on the left on the second page of this document: http://www.tmrservizi.it/files/arsenio/inverter/powerone.pdf

    Thanks
  • Mike GreenMike Green Posts: 23,101
    edited 2011-05-24 09:14
    +T/R and -T/R are the signal lines for the RS485 signal. RTN is probably the "return" or ground line for the circuit.

    You will need some kind of RS485 receiver IC as shown in this Nuts and Volts Column from Parallax's website. In your case, you're only using the MAX483 for receiving, so you'll only use DATA_IN and TX_RX will be permanently connected to ground. You would use SERIN to actually receive the data.
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