User Manual

Figure 6: Two examples of ICs – an 8-pin and a 20-pin dual-inline package (DIP). In this package style, pin 1 is always

identified as the first pin anticlockwise from the package notch marking.

Integrated circuits (also known as ICs or chips), are marked Un. For example the I/O buffer chips are

U3, U4, and U5 (these are near the middle of the board), while the Atmel microcontroller is U8 (this

is below and to the left of U3 to U5). It is important to understand IC pin numbering. If the chip is

orientated so that the end with the semi-circle notch is to the left, then pin 1 is the leftmost pin in the

bottom row. Pin numbers increase in an anti-clockwise direction from there, as shown in Figure 6.

Knowing this means that the schematics in Appendix A can always be related to the pins on the ICs

on the Gertboard.

Headers (the rows of pins sticking up from the board) will be a frequently used component on the

Gertboard. They are labelled Jn. For example, there is a collection of headers along the left edge of

the board. They allow you to access the three chips on the left side of the board: J28 on top for the

analogue to digital chip, J29 below that for the digital to analogue chip, and J25 below that for the

Atmel microcontroller. It is a bit difficult to see the boundary between these headers on a fully

assembled board; it‟s much clearer on the blue and grey diagram in Figure 5. On the Gertboard circuit

board, each header with more than two pins has pin 1 marked with a square around it and a dot next to

it. The dot is most useful on the assembled board, but these dots don‟t appear in the blue and grey

diagram, so you can use the squares to find pin 1 there.

Not everything labelled Jn is a collection of pins. J1, at the bottom of the board, is the location of the

socket that connects the Gertboard to the Raspberry Pi. J19, at the top of the board (right of centre) is

a block of screw terminals that allow you to easily connect wires from a power supply and a motor.

Power on the Gertboard

Power pins are marked with their voltage, e.g. 5V or 3V3 (this means 3.3V). A 5V power supply

comes onto the board from the Raspberry Pi, and if you need this voltage it can be accessed from the

lower pin (marked 5V) on header J24 on the lower right-hand corner of the board. Ground is marked

with GND or a  symbol.

The supply voltage (the voltage that acts as high or logical 1 on the board) is 3.3V. This is generated

from the 5V power pin in the J1 header by the components in the lower right corner of the board. To

send the 3.3V power supply to the components on the Gertboard, you need to install a jumper over the

top two pins of the header J7. It is near the lower right corner of the board; see the photo and diagram

in Figure 7. The open collector and motor controllers can handle higher voltages and have points to

attach external power supplies.

1 2

1 2 4

3 5 86

20 19 18

9 10

1112

1516