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Joined: Sat Dec 22, 2012 3:59 pm

3 wire SPI; hardware or bitbang ?

Sat Dec 22, 2012 4:38 pm

Hello everyone.
I would like to interface the Raspi with the CCD sensor from an optical mouse in order to get access to the raw pixel data.
The optical mouse I have available is based on the ADNS-5020-EN (http://www.avagotech.com/pages/en/navig ... s-5020-en/) which can be accessed through a 3 wire SPI bus.

For a first project, I would like to replicate what has already been done with an Arduino on this web page: http://www.bidouille.org/hack/mousecam

I am very new to the Raspberry Pi (received it this week) and I am more of a software (image analysis) than a hardware/low level protocols person.

My main question is, "can the hardware SPI port be used with the 3 wire setup or do I need to bitbang the whole thing on regular GPIO pins ?"
In other words, does the hardware SPI support bidirectional (half duplex) communication on only one of the 2 data lines (MISO or MOSI) ?

I have installed Adafruit's version of Raspbian that ships with SPI ports already available in /dev/ and I have downloaded the wiringPi bindings for python.

Any help/pointers deeply appreciated.


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