Is there a chip that is just a parallel in / serial out shift register but with integrated internal pullups?
I could use a full-blown I/O expander but I really just need more momentary button inputs. I don't need outputs and I would rather not bother adding resistors or with writing commands to initialize the chip.
Logic integrated circuits such as shift registers normally do not contain pull up resistors on their input(s). This is because they are normally connected to a totem pole driver. Such a driver eliminates the need to avoid floating inputs.
Also, pull up resistors require current when the input is driven toward the opposite power rail. Even though adding internal pull up resistors may not change the overall behavior of the chip, designers will avoid parts if they unnecessarily add to the over all power demand.
Based on your comments and your question, consider an old ps/2 keyboard. It is essentially a switch matrix with a built in decoder chip which may fullfill your requirements. The chip scans the switch matrix, debounces the switches and converts button presses & button releases into a serial stream of data.
Added later...
Here is a description about connecting a ps/2 keyboard to an Arduino. Included are schematics, code examples and supporting library.
(USB keyboards are not well suited for this purpose as they require a USB Host. As most Arduinos do not have this, a USB Host shield is required.)
