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RS 232 communication on propellor — Parallax Forums

RS 232 communication on propellor

faizzzfaizzz Posts: 7
edited 2009-12-05 14:45 in Propeller 1
Hi

i intend to connect three RS 232 links to my propellor for an application im developing. Could anyone please assist me regarding the possible circuitry and the programming involved. How many pins do i need to allocate on the propellor. Would using just two pins for RX and TX suffice?

Regards

faizzz

Comments

  • Dr_AculaDr_Acula Posts: 5,484
    edited 2009-12-04 13:16
    Two pins (per port) are fine. Handshaking lines DTS etc are not needed when you have high speed links with buffers (which the propeller code examples all have).

    You can use a max232 and put 1k resistors in series between it and the prop. These are because the max232 is run on 5V. The resistors go on pins 9 and 12 of the max232.

    OR you can use a max3232 which runs on 3V, doesn't need those resistors (but is a bit harder to get and costs a little more).

    Each max232 will give you two serial ports. Three serial ports will need a couple of max232 chips.

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    www.smarthome.viviti.com/propeller
  • LeonLeon Posts: 7,620
    edited 2009-12-04 13:19
    Use a MAX3232 for the interface.

    Unless you need flow control, you only need two pins for each link.

    UART software is in the Object Exchange.

    Leon

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    Amateur radio callsign: G1HSM
  • dMajodMajo Posts: 855
    edited 2009-12-04 18:56
    Dr_Acula said...
    Two pins (per port) are fine. Handshaking lines DTS etc are not needed when you have high speed links with buffers (which the propeller code examples all have).

    You can use a max232 and put 1k resistors in series between it and the prop. These are because the max232 is run on 5V. The resistors go on pins 9 and 12 of the max232.

    OR you can use a max3232 which runs on 3V, doesn't need those resistors (but is a bit harder to get and costs a little more).

    Each max232 will give you two serial ports. Three serial ports will need a couple of max232 chips.

    Or you can use a MAX3387E. It runs on 3V and one IC (thus one set of capacitors, one time pcb area) is enough for all three serial ports.

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  • Dr_AculaDr_Acula Posts: 5,484
    edited 2009-12-04 22:14
    And I should have mentioned there is a nifty object in the Obex that can run 4 serial ports on one cog. So the coding is pretty much all done and the hardware could be just one extra chip.

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    www.smarthome.viviti.com/propeller
  • faizzzfaizzz Posts: 7
    edited 2009-12-05 13:15
    thanks alot DR Acula, i found the object and wow!
    btw, one more thing i wanted to ask:
    would it be better in your view to use the prop plug and convert USB to RS 232, to connect to the computer for code transfer, or interfacing an RS232 to have a simple RS232 transfer?

    Regards

    And thank you once again! [noparse]:)[/noparse]
  • LeonLeon Posts: 7,620
    edited 2009-12-05 14:45
    If you are just transferring data to/from the PC, it makes sense to do it via the Prop Plug. Especially as serial ports on PCs are an endangered species.

    Leon

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    Amateur radio callsign: G1HSM
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