Forums

SPI Communications

Started by rickpres22 May 18, 2005
> ... there is a subtle hint that the data in the receive buffer is
used...

OK, I agree, that _is_ mysterious. I have a plan, an SPI loopback.

Perhaps the simplest SPI slave, a single tri-state buffer with /CS,
controlled by a BX-24 pin, can loop MOSI to MISO. We should be able to
see what, and how much of it, goes where. Tom
Tom Becker
--... ...--
GTBecker@GTBe... www.RighTime.com
The RighTime Clock Company, Inc., Cape Coral, Florida USA
+1239 540 5700


--- In basicx@basi..., "Tom Becker" <gtbecker@r...> wrote:
> We should be able to see what, and how much of it, goes where.

I just used a logic analyzer. ;)

Don



> ... I just used a logic analyzer. ;)

Tools is where it's at, man. What have you learned? Tom
Tom Becker
--... ...--
GTBecker@GTBe... www.RighTime.com
The RighTime Clock Company, Inc., Cape Coral, Florida USA
+1239 540 5700


--- In basicx@basi..., "Tom Becker" <gtbecker@r...> wrote:
> > ... I just used a logic analyzer. ;)
> Tools is where it's at, man. What have you learned?

That's how I discovered that the data existing in the read buffer is
written to the SPI device to elicit the return data. Prior to that
experiment, I assumed that zero or other arbitrary data was written to
get the slave to return the desired data.

I described the I/O sequence in this message:
http://groups.yahoo.com/group/basicx/message/18831



> ... the data existing in the read buffer is written to the SPI
device...

I don't see why that doesn't work with the FRAM. I see 255s coming
back. CS is low through the transfer? Tom
Tom Becker
--... ...--
GTBecker@GTBe... www.RighTime.com
The RighTime Clock Company, Inc., Cape Coral, Florida USA
+1239 540 5700