Have you had good or bad experiences with SPI(CLK,Data,Enable) bus for increasing port outputs.
What set up did you have for your experience:
- bus on same board as micro?
- bus fed by 3 wire cable to seperate board from micro?
I'm using a 3 wire bus with latches to create 56 outputs on a seperate print with a cable of ~1.2 meters.
Problem is that sometimes outputs are are spontanously flashing which should not happen.
i implemented a spi interface in software on both sides
between a 51 micro and an early pic .. and is was very reliable !
the reason of this approach was to use the pic as a power manager
and as a watchodog for the 51 . We couldn't afford the 51 to crash and damage other machinery .. This approach was great !
I forgot to say the reasons why i chose this approach
1) the protocol does't require special circuitry . is easy to implement in
software .
2)also several devices can be addressed .
3) is more inmune to noise .. specially in industrial enviroments
I have used SPI comunication in many aplications( port expander MAX8301, A/D converters, FLASH,E2PROM,RTC..) and as far I'm concerned it's wery reliable at least for me.