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SPI interface

Hi, I'm a newbie so excuse the dumb question. Trying to implement an SPI interface between one master and multiple slaves. One of the slaves is on an external board and i've only got 3 pins available for connection to Master board(Its a PCB and i'm adding this slave). Now, the SPI interface requires 4-wires(I need the Slave Select) if the slave is "transmit only" can i leave the SDI pin unconnected (Datasheet doesn't say much)??

P.S:Devices are pics.

Thanks

Reply to
gman052002
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You could do it with some special software....... Assume devices 1,2 and 3 are served by SlaveSelect. The 4th device can "listen" to all commands over SPI and you can give it a software address of 4 so it will only respond to its own address.

Reply to
martin.shoebridge

You can tie it to Vdd or Vss, preferably through a resistor.

My condolences. Be sure to study all the errata documentation carefully.

Best regards, Spehro Pefhany

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Reply to
Spehro Pefhany

I would think not, because if your "transmit only" is sending all of the time, it would step on the transmissions from all of your other slaves, unless you've worked out some kind of protocol to get around that. And if it's not free-running, how do you tell it when to send?

And, along with Spehro, I send my condolences. ;-)

Good Luck! Rich

Reply to
Rich Grise

if they are all pics you can probably use the SPI pins as general IO anyway and devise your own interface.

I recently knocked together a circuit to program a SPI PLL device from just

1 wire conected to a rs232 (well and ground as well of course) using 3 cmos schmitt triggers wired as delays and 'diode or' diferent length pulses would generate data, clock and latch.

writing ~,p,@ would generate 0,1,latch.

colin =^.^=

Reply to
colin

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