2 replies to this topic

[Nicolai]

Hi,

Looking at something like this, it uses A LOT of pins.

Is there some way I can reduce the pin usage, on things like these? 

I will run out of pins if I use things like this

 

[Nevyn]

There are a few options, the most common one people have used here is to use a single 74HCT595 shift register.  This will allow you to use three pins and have 8 outputs per chip.  You need the HCT version as this will allow you to use 3.3V outputs to communicate with the chip.  There's a fair amount of examples in the forums here for using these chips.

 

There are other chips such as the MCP23S17 which has 16 input/output pins.  This one uses SPI but there are I2C versions out there.

 

Hope this helps,

Mark

[Paul Newton]

A nice thing about these serial to parallel chips is that all the outputs change at the same time. Individual GPIOs have to be changed one at a time.
Not always a problem, but sometimes important.
Paul