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  1. #1
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    SPI extender module for 40 meter

    Hello all,

    I need to design a extender circuit for SPI signal which is 1 MHz clock signal. I designed a circuit with SN65C1167 and it works over 40 meter but we need to add one cable more because it works with RS485. I'm looking for SPI extender which already need 3 cable which are CLK, DATA and GND.

    I saw some circuits as you can see links. Two designs are working with WS2811 series and CLK is 400 kHz and 800 kHz. One of that design uses opto and a IC. I try to use 6N137S opto and level shifter circuit at attached but level shifter doesn't charge cable. I'm thinking to use line driver after opto. Could you have any idea for this problem or do you know what that IC ?

    http://www.led-studien.de/repeater-fuer-ws2801-pixel/




    •   Alt18th May 2017, 08:52

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  2. #2
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    Re: SPI extender module for 40 meter

    Hi,

    not clear what you need.

    If you use RS485 signals then the solution should be like this:
    * SCK TTL level --> RS485 transmitter IC --> 40 m twisted pair --> RS485 receiver IC --> SCK TTL levels
    * CS TTL level --> RS485 transmitter IC --> 40 m twisted pair --> RS485 receiver IC --> CS TTL levels
    * MOSI TTL level --> RS485 transmitter IC --> 40 m twisted pair --> RS485 receiver IC --> MOSI TTL levels
    * one GND connection
    * MISO TTL level <-- RS485 receiver IC <-- 40 m twisted pair <-- RS485 transmitter IC <-- MISO TTL levels

    maybe you could use an ethernet cable (4 pairs)

    CS is slow and doesnīt need to be run over RS485. You may run it single ended and GND on the remaining wire.
    This is no perfect solution...
    Maybe you could use cable shield for (additional) GND connection.


    Klaus



  3. #3
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    Re: SPI extender module for 40 meter

    I need only DATA and CLK for transmission, no need to data back. This is lighting luminarie which is working like WS2811 protocol.



  4. #4
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    Re: SPI extender module for 40 meter

    Hi,

    I just had a look at WS2811.

    * it is no SPI
    * it doesnīt need a clock

    Only dat_in and data_out

    --> you should clarify this.

    Klaus



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    Re: SPI extender module for 40 meter

    Please check WS2801.



    •   Alt18th May 2017, 12:37

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  6. #6
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    Re: SPI extender module for 40 meter

    Hi,

    Please check WS2801.
    thank you to keep us busy.

    It would be more motivating if you give the informations rather than let us find out..

    ***
    It still is no SPI.

    It is just a synchronous serial interface.

    And the solution is similar than already given in post #2, just replace the signal names:
    * CKO CMOS level --> RS485 transmitter IC --> 40 m twisted pair --> RS485 receiver IC --> CKI CMOS level
    * SDO CMOS level --> RS485 transmitter IC --> 40 m twisted pair --> RS485 receiver IC --> SDI CMOS level

    Klaus



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    Re: SPI extender module for 40 meter

    Quote Originally Posted by KlausST View Post
    Hi,


    thank you to keep us busy.

    It would be more motivating if you give the informations rather than let us find out..

    ***
    It still is no SPI.

    It is just a synchronous serial interface.

    And the solution is similar than already given in post #2, just replace the signal names:
    * CKO CMOS level --> RS485 transmitter IC --> 40 m twisted pair --> RS485 receiver IC --> CKI CMOS level
    * SDO CMOS level --> RS485 transmitter IC --> 40 m twisted pair --> RS485 receiver IC --> SDI CMOS level

    Klaus
    Thank you for information but I also designed RS485 solution. I need to decrease 4 cable (CKI A and B, SDI A and B) to 3 cable (CKI, SDI and GND).



  8. #8
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    Re: SPI extender module for 40 meter

    Hi,

    please give all informations at once. Not every post a new information.

    Why now "A" and "B"?
    * Are this for two end devices?
    * or are this the differential lines of one RS485 signal?

    If RS485: then you canīt decrease wires. Each signal needs a differential twisted pair of wires.

    Klaus



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    Re: SPI extender module for 40 meter

    Those are the differential lines of one RS485 signal. I already did I'm looking for different solution or suggestions. As you can see link below, it says 200 meter communication length and I think it is not differential solution. Could it possible ?

    http://myneopixel.com/dc5-12v-spi-am...12b_p0935.html
    Last edited by Knife; 18th May 2017 at 16:43.



    •   Alt18th May 2017, 16:24

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  10. #10
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    Re: SPI extender module for 40 meter

    Hi,

    I donīt think a single ended soultion can work reliably.

    Klaus



  11. #11
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    Re: SPI extender module for 40 meter

    KlausST, thank you for suggestion and information.



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