Faster alternative for SPI.transfer

Projects Programming
1

Hi,

I am using three SPI chips with Arduino Mega. Right now i am using SPI.transfer to communicate with the chips. It is taking 12-16usecs for transferring two bytes. is there a faster way to do this?

2

It looks like you are running SPI at 1 MHz. See SPI - Arduino Reference and check the data sheets for your devices to see if you can go any faster.

3

Thank you. I will check the devices spec.
Just to be clear: SPI_CLOCK_DIV2 is 8Mhz right. So imy devices should be able to operate at 8Mhz.? Am I correct?

4

Ok that worked. Thank you.

5

Yes, 8 MHz is the fastest you can go.
You can gain a little more speed by using direct control vs SPI.transfer:

SPDR = dataArray[0];  nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop;
SPDR = dataArray[1];  nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop;
SPDR = dataArray[2];  nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop;
SPDR = dataArray[3];  nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop;
SPDR = dataArray[4];  nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop;
SPDR = dataArray[5];  nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop;
SPDR = dataArray[6];  nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop;
SPDR = dataArray[7];  nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop;

Not using for loop saves about 12uS/byte, not waiting for SPI interrupt but just timing it out saves some time too - I have achieved 45 bytes in about 47uS doing this.
(17 clock cycles per transfer I think it works to).
Need some assembler thing at the top of the sketch, I don't recall what it is, have to look at a sketch to see.