Microcontroller Bootcamp (7)

There are countless devices available with I²C interfaces, including simple port expanders, EEPROMs and a wide variety of sensors. In the final instalment of our Bascom course series, we show you how the I²C bus works. As usual, the main focus is on interesting demo applications.

On the Serial Peripheral Interface (SPI) bus, the actual data travels bit by bit over one line—for example from a microcontroller to a display, an EEPROM or an SD card. In most cases it’s also desirable to be able to read data, so you need a second line to provide a return channel for the data.

One of the longest chapters in the ATmega328 data sheet is the one that describes its three timers. The timers can be used in so many different ways that we only have space here to look at a small fraction of the possibilities. The main application areas are in measuring time intervals and frequencies, and in generating various signals including PWM output

First let’s see what it takes to drive a display. Various types are available, including graphic and text displays. Text displays range from tiny with a single line of 8 characters, to large with four lines of 20 characters.

Although most PCs nowadays have dispensed with the traditional serial interface, it is still widely used in the microcontroller world. This interface was originally developed to transfer serial data over a conductor. The individual bits obediently travel down the wire one after the other. The bit timing is precisely defined so that the receiver can make sense of the serial bit stream.

Microcontrollers, including the ATmega328 on the Arduino board, have many different types of input. They include analog inputs, which can be used to measure voltages, and digital inputs, which can only detect whether a signal level is high or low. This can be used to read the state of a button or switch, among other things.

You might ask why you should use a microcontroller when it’s possible to do so much with ordinary analog electronics. At first glance, this looks like a good question. New microcontrollers with more features, higher performance, higher clock rates and even more memory are appearing all the time, but the first demo program for every one of them invariably makes a LED blink.