We are witnessing great progress in all areas of technical science. Much of that progress we can attribute to the development of processing power in our PCs, which have enabled development of new powerful programming tools running on our PCs. In the field of electronics there are many tools that we use daily and which are indispensable to our work. The same goes for electronics components, especially microcontrollers, which have progressed tremendously in the last 15 years.

Bascom’s Debounce statement solves this problem, by checking the switch’s state over again a bit later, when a level change is detected at an input pin. For example, if Debounce is configured to recognise a falling edge at an input pin (a logical level change from High to Low), it will delay the program execution for 25 ms and then check the input pin again to see if it is still at a logic “0” or not. If it is, an associated subroutine will be executed.

I had a requirement where a 20-pin microcontroller had to drive one LED display plus other peripherals. To drive the LED display, required 8 pins that were not available, because they were already used by other peripherals. After a literature search, I found a cheap shift register which performs like the PCF8574 (which is not cheap at all!).

Most AVRs contain PWM hardware, especially the newer ones, which typically have two or more PWM units built-in. A PWM signal is one in which the ratio between a pause and a signal is changing as seen in Figure 1.