SPI Commands Operating Speed

[gunayburak]

Thanks Henrik I'll give it a try ..

[Art]

You’ll get data in & out of the master faster than PBP if you express both the read and write routines in a verbose fashion such as below write routine.
It might need delays between pin writes that could be as short as @nop commands, and the routine is also a candidate for RWM error without adding
a shadow register for port latching (mind you, PBP SHIFTOUT command is probably no different). It’s probably faster again if the chip has hardware SPI.

byte data_out'

WriteSPI:
    ‘ bit 7
    SPICLOCK = 0’
    SPIOUT = 0’
    SPICLOCK = 0’
    SPIOUT = data_out.bit7’
    SPICLOCK = 1’
    ‘ bit 6
    SPICLOCK = 0’
    SPIOUT = 0’
    SPICLOCK = 0’
    SPIOUT = data_out.bit6’
    SPICLOCK = 1’

    ‘ and so on for the rest of the bits…
	
RETURN

[HenrikOlsson]

I just tried SHIFTOUT with 64MHz oscillator and the clock frequency is 300kHz. At the same speed the MSSP module would be able to spit out data Fosc/4 but then your code wouldn't be able to keep up with feeding the module so it won't be a sustained 16MHz bitrate.

/Henrik.

[gunayburak]

Thanks for all the answers ..

I measured the SCK frequency 333 khz at 64 mhz so I wish pbp had a modification parameter for it (since we can't use all the pins for hardware SPI purpose)
Well , Maybe ART's suggestion may work .. as a subroutine .. Why not .. I'll try .. It shall be faster after all ..

Thanks once more to both of you

[Art]

It’s doesn’t “might” work, I play MP3s by using hardware SPI to read from SD card, and the above routine to write to the MP3 decoder.
Mind you, there are a few varieties of SPI you might have to experiment with (see the configuration of any pic with hardware SPI).