One embedded system hardware device that has not been covered yet is the keypad. Applications for it range from specialized calculators, combination locks, or simple data input keypads. Normally these have their buttons arranged in rows and columns so that they can be scanned by the host computer, reducing the number of I/O ports necessary. You’ll do the same in this chapter but using the DIP form of the PCF8574 I/O chip to avoid using up precious GPIO ports.
You have seen this chip before as part of the PCB adapter to the LCD in Chapter 4. The project presented here will make use of the dual inline ...
