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On 12/06/10 10:05, razvan_ionut_stoian wrote:
> Hi.
>
> Does anybody know how to modify (hardware and software) a typical SPI
> interface (CLK/MOSI/MISO/CS) into a 3-wire SPI (no MOSI line)?
>
> In order to receive a word from the slave, one has to send a dummy command
> from master to slave. Since there is no MOSI line, how can the serialization
> of the received data be possible?
Easy, it's not synchronous. You assert CS, clock a command to the
device, then depending on implementation you signal the device to
transmit (by toggling CS or stopping the clock) or you don't. When the
slave transmits the master keeps clocking till the slave finishes.
Check the chip's datasheet it should give you a detailed protocol
breakdown. If the hardware SPI interface can handle it is a different
question :) Doing it in software on a couple GPIO pins wouldn't be hard
tho.
- --
Jason Stahls
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