The Gertboard is an input/output (I/O) extension board for the Raspberry Pi computer. It fits onto the GPIO (general purpose I/O) pins of the Raspberry Pi (the double row of pins on the upper left corner) via a socket on the back of the Gertboard. A bit of care is required when putting the two devices together. It is easy to insert just one row of pins into the socket, but all of the pins need to be connected. The Gertboard gets its power from those GPIO pins, so you will need a power supply for the Raspberry Pi (RPi) that is capable of supplying a current of at least 1A.
The Gertboard has collection of functional blocks (the major capabilities of the board) which can be connected together in a myriad of ways using header pins. The functional blocks are:
12x buffered I/O
6x open collector drivers (50V, 0.5A)
18V, 2A motor controller
28-pin dual in line ATmega microcontroller
2-channel 8, 10, or 12 bit Digital to Analogue converter
2-channel 10 bit Analogue to Digital converter
The location of these blocks on the Gertboard is shown in Figure 2.
Figure 2: Functional blocks diagram: the key blocks are identified by coloured boundary marking. Please note that the appearance of some components can vary.
This annotated photo of a populated (fully assembled) Gertboard shows where the functional blocks are located. Some of the blocks have two areas marked. For example, the turquoise lines showing the Atmel ATmega chip not only surround the chip itself and the header pins next to it (on the lower left) but also surround two header pins near the bottom of the board, in the middle. These two pins are connected to the Atmel chip and provide an easy way to interface the GPIO signals from the Raspberry Pi (which are in the black box) with the Atmel chip.
There is no connection (other than power and ground) between the different functional blocks on the Gertboard. The many headers (the rows of pins sticking up from the board) allow you to make these connections, using straps and jumpers. See Figure 11 on page 18 for an example of how these are used to connect the various blocks together.
Figure 3: Photograph showing straps (the coloured wires) above, and jumpers below. Straps connect two parts of Gertboard together, whilst jumpers conveniently connect two adjacent pins together.
Labels and Diagrams
As you get to know the Gertboard and make connections between the various blocks, you will be guided extensively by the white labels on the circuit board. At this point, we would like to introduce the diagram, shown in Figure 5, which we will use to show you how to wire up your Gertboard for the test programs.
Figure 4: Photograph of the Gertboard
Figure 5: Diagram representing a bare Gertboard circuit board. The blue elements correspond to the white lines and text, and the gray elements correspond to the silver coloured pads.