SPI basics

[flotulopex]

I understand the difference between both asynch- and synchronous transmission and the advantage of the second one.

Does SPI require always 2 way communication setup? I don't see my display sending some data back to the PIC, does it?

What is the RS line for?

Starting to build-up an SPI communication, I'll need to configure the SSP module by firstly switch it ON (SSPCON.5 = 1). Then, according to my display's datasheet, I think the data is transmitted on rising edge but the setting depends on the CKP mode which I don't know what it is about ?!

Next, there seems to be several ways to send the data; either using SHIFTOUT command or via registers (SSPBUF). Which one is the better way of doing?

What about speed. My display works at 400kbits/s (or am I wrong), what will be the "safest" setting?



PS: I'l be on holiday this week...

[Dave]

What is the RS line for?

The RS line on all displays I have seen is used for determining whether the data going to the display is a command for the display or data to be displayed... It should be in the documentation for the display you are using...

Dave Purola,
N8NTA

[Normnet]

Does SPI require always 2 way communication setup? I don't see my display sending some data back to the PIC, does it?

SPI both sends and receives a byte at the same time.
Just send: SSPBUF = $FF (anything) or receive: dummy = SSPBUF if one way.

Is your program working with SHIFTOUT?

Norm

[rsocor01]

Does SPI require always 2 way communication setup? I don't see my display sending some data back to the PIC, does it?

Yes, the display can send some data back to the PIC. I don't know about this particular display, but most GLCD can send data back to the PIC. This data can be anything from a Register value to the RGB value of the pixels that are been displayed in the screen.

However, if you prefer you can hardwire the display for write-only.

Robert