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SPI extender module for 40 meter

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Knife

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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 ?

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



 

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 doesn´t 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
 

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

Hi,

I just had a look at WS2811.

* it is no SPI
* it doesn´t need a clock

Only dat_in and data_out

--> you should clarify this.

Klaus
 

Please check WS2801.
 

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
 

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).
 

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 can´t decrease wires. Each signal needs a differential twisted pair of wires.

Klaus
 

Last edited:

Hi,

I don´t think a single ended soultion can work reliably.

Klaus
 

KlausST, thank you for suggestion and information.
 

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