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MSP430 SPI(USI) in half duplex mode

Ayus
Intellectual 825 points 

Hello,

I am a new to SPI protocol.
We are using MSP430G2452 and there is some shortage in the I/O pins for our application. 
We wonder whether we could save pins with the SPI (USI) port.

As the SPI is a full duplex(transmit and receive simultaneously), 
and our communication is always only one-direct(half duplex)
is it possible to use only SCLK and SDO pins to communicate and 
use SDI pins for other purpose.
Is this kind of usage allowed in MSP430?

Regards.
  • 0
    Guru 227245 points

    Ayus said:
    is it possible to use only SCLK and SDO pins to communicate and use SDI pins for other purpose.

    Yes. If the SDI pin isn't selected, the USI will read '1' when clocking the bits in - same as if the pin were used, but no slave connected. The USI doesn't care whether there is someone out there. It just puts bits out and pulls bits in. Whereever they may go to or come from.

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