SPI pins set in stone?

Projects General Guidance
1

Do the MOSI MISO and SCK pins have to be 11, 12 and 13 ?

I have always used them as such, but I connect a chip better in a project if I use 12, 3 and 4.

We define the latch , clock and data pins and set them as outputs, so is there a choice?

I think I went into it once but I am confused and sleep deprived :slight_smile:

2

Yes, those pins are set in stone, if you want to use the hardware SPI peripheral.

You can always "bit bang" an SPI protocol using digitalWrite() functions (or lower-level writes to PORTx registers) to any pins that you want, but this will be much slower, of course.

--
The Rugged Circuits Yellowjacket: 802.11 WiFi module with ATmega328P microcontroller, only 1.6" x 1.2", bootloader

3

Thanks RuggedCircuits

I thought so, but when I hooked it up with the other pins, it works but very unstable and flickers the LED display, unless I put my finger across the output pins , then its fine !

I was going to waste a bit of time on it, but as soon as I connected the scope ground to the -ve supply, the display went off anyway, so 5 minutes connecting three jumpers looks the logical way to go !

4

That's an odd problem. Did you roll your own function or use ShiftOut?

5

There's also fat16lib's software SPI, he's got it running pretty fast.
I go with hardware pins on anything I do.