SPI for MCP23S17

[Franck26]

Hello everybody,

Did someone have already used the GPIO MCP23S17?

I'm trying to set the SPI SFR of a pic 24HJ to communicate with this GPIO but I have some problem to understand the MCP23S17 datasheet.
I can't determine the SCK idle state, when the input have to be sample, etc...

It would be helpful if someone have already set the SPI register of a pic (doesn't matter which pic) to use this component.

Thanks for your help.

Franck.

[PCM programmer]

Download the MCP23S17 data sheet:
http://ww1.microchip.com/downloads/en/DeviceDoc/21952b.pdf
Look at Figure 2-5, on page 32. Look at the line where it says
"SCK" on the left side. It tells you the two SPI modes that are
supported by the chip. The modes are given in binary notation.
You can then use the MODE parameter in the #use spi() statement
to specify the spi mode.

[Franck26]

Thanks for your reply,
I've already downloaded the datasheet (and the AN), but I haven't understand what means MODE 1,1 and MODE 0,0...
And I haven't find anything about it in the datasheet. Is it a general term to specify the SPI?

About the #use spi(), I would like to keep the software compatible with oher compiler, so I prefer to work directly with the SFR.

Can you tell me more about MODE ?

Thanks,
Franck.

[PCM programmer]

There are four SPI modes, based on the clock to data timing relationship
and the clock idle state. See this page for an explanation:
http://elm-chan.org/docs/spi_e.html

See my post near the end of this thread. It shows how to specify the
SPI mode with the CCS setup_spi() function.
http://www.ccsinfo.com/forum/viewtopic.php?t=33255

[Franck26]

Thanks for the explanation.

I've tried the defined shown on your post (http://www.ccsinfo.com/forum/viewtopic.php?t=33255):

[PCM programmer]

I don't have the PCD compiler, so I can't really help. I only have PCB,
PCM, and PCH.

[Franck26]

OK, that's fine,
Can you just tell me if SPI_XMIT_L_TO_H is a parameter to control the polarity of the clock pin or of the data pin?

Thanks,
Franck.

[PCM programmer]

In a 16F or 18F PIC, the SPI_XMIT_L_TO_H parameter sets
the CKE bit = 1. Here is the definition of the CKE bit for those PICs:

[Franck26]

OK, Thanks,
I have the CKE bit too in the 24H SFR.
I will try that this week.

Franck.