I've been trawling and sent myself to sleep reading datasheets but someone here may know this already.
I want a simple method of polling 32 digital inputs using a single 8 bit port. - (simple and rubust is key!
)So... use 4 x 74HC244 (Non inverting input buffer with enable), 8 digital inputs go to each chip. Each chip has an enable pin, select and read each one in turn.. nice simple solution.
But I cant find a version with all the inputs on one side of the chip and the outputs on the other, thus giving a much tidier PCB layout.
I also understand that multiple 74HC244 can add to much capacitance to the bus. The digital states being read will be very slow (mechanical switches ) but I would still wish to select and read each chip each one at a decent rate.
Any Ideas?
I was avoiding using the 74HC574 but currently looks the most promising.
I could also use an input expander using SPI but I've already got loads of SPI devices and routing the tracks to so many devices could get messy.
John.
