can i use I/o Port pins of a processor as four SPI pins? i

Hi all,
I want to do an experiment . i want to use processor I/0 pins as SPI pins namely MOSI,MISO,CLK , SS . can i use it ? if not why ? if yes any additional changes i have to make?
warm regards,
Ravi Kulkarni.

Are you asking if you can integrate this functionality into the kernel, or are you just wanting to write your own SPI interface using these general purpose I/O pins?

Running GPIO pins as an SPI interface is easier from the master side, because you control the clock rate. It is a matter of making sure all of the relevant pins transition at the same time (ideally they will all be on the same port), or at least in the right order. But it won't be fast. From the slave side, you would need to rely on interrupts triggered from the clock pin, and you may not be able to respond to the interrupt in time (within the SPI clock cycle).

Originally Posted by neonsignal Are you asking if you can integrate this functionality into the kernel, or are you just wanting to write your own SPI interface using these general purpose I/O pins? Running GPIO pins as an SPI interface is easier from the master side, because you control the clock rate. It is a matter of making sure all of the relevant pins transition at the same time (ideally they will all be on the same port), or at least in the right order. But it won't be fast. From the slave side, you would need to rely on interrupts triggered from the clock pin, and you may not be able to respond to the interrupt in time (within the SPI clock cycle).

I want to use this functionality from kernel. set up a module and transfer a data. there is a driver called /driver/spi/spi_bitbang.c
this driver helps to make use four gpio pins as spi pins. how to write a kernel module which helps me to use this particular driver?. and btw there is no SPI slave support in linux kernel. so i av to use spi masterr only. can anyone please guide me on this ?
warm regards,
Ravi Kulkarni.

Perhaps worth at looking how other people have made use of it, for example, this AT91 driver. Hope that is helpful.