Gertboard Raspberry Pi Expansion

The "Gertboard" version 1 is an I / O expansion board for the Raspberry Pi computer. It connects to the computer through the GPIO pins and provides additional interfacing capabilities for projects. The board has a large variety of circuits for experimentation purposes, and provides switches, LEDs, ADC, DAC, motor driver, and an Atmel microcontroller. The board also has accompanying software written in a high-level language, which is freely available.

Mr Gert J. Van Loo

Designed and developed by Mr Gert J. Van Loo and named after him, he was also the designer of the first Raspberry Pi called the "Alpha Board". He studied at Delft University of Technology in Netherlands / Nederland and therefore his standard of education is much higher than that found in the UK. The name is a variation of Gerhard where "Ger" means spear and "Hard" means strong or brave, therefore Gertboard probably means a strong brave board. Nederland is of course very famous for the Dutch painters and mathematicians of the 17th Century, such as Jan van Goyen, Rembrandt Harmenszoon van Rijn, and Christiaan Huygens the famous mathematician. Gert van Loo now goes into the list as well as the famous inventor of educational tools.

Expansion Capability

The board provides six major areas of expansion capability to the Raspberry Pi explained in the following sections of this article. It has 12-buffered I/O lines for general-purpose I/O functions, six open collector drivers to switch and drive loads, and one high voltage motor controller. There is also a 3.3 V Atmel AVR microcontroller thrown-in for fun, two-channel analogue-to-digital converter (ADC), and a two-channel digital-to-analogue converter (DAC). In addition, the board provides 3 switches, and 12 LEDs for basic I/O experimentation.

Kits

The first version of the board arrived in kit form to reduce the final cost to the consumer. If you own one of these boards then you will need to assemble it by soldering all the components in place. As you can see from the photograph above, some of the components are surface-mount devices (SMD), therefore you will need excellent soldering skills, and good eyesight to make a decent job of it. You will need a good quality fine tipped soldering iron and some quality solder. Please note that you should not use a soldering iron if you are under age and unsupervised.

Strapping Area

As you can see from the diagram above, each aspect of the expansion is completely separate from the rest of the circuitry; however, the arrangement of each section is thoughtful and makes using the board simple. The ribbon cable from the Raspberry Pi GPIO connects to the J1 header on the Gertboard shown in orange. These pins then map to header J2 shown in brown, which forms the "strapping area". This area is where you can choose which pins of the Raspberry Pi GPIO you wish to use. You can then connect those header pins to any of the expansion sections of the board depending upon your project.

Open Collector Drivers

The ULN2803AGP IC provides six open collector drivers, which are useful for driving low power loads such as LEDs. This is an octal IC with eight drivers, however only six made it to the input / output header pins. This section is completely separate from the rest of the circuitry and its use is optional.

Atmel Microcontroller

The Atmel microcontroller is completely separate from the rest of the circuitry and its use is optional, and the board will work fine without it. The Raspberry Pi UART connects to the microcontroller UART for data communication. The rest of the microcontroller ports route to a separate header and you can use them as you wish.

Buffered I/O

There is a section providing 12 bi-directional I/O lines based on the SN74AC244 buffer chip. Each line consists of two buffers to facilitate bi-directional data flow. The IC requires manual setting of the jumper pins "J In" and "J Out" for each line in order to set the direction of data flow. This "AC Series" IC expects CMOS inputs and provides CMOS outputs. If you need TTL outputs, then these are not available.

Motor Controller

The board has the L6203 motor controller IC, which is a full-bridge driver that is normally used to power a single motor. If you need two motors for a robot car, then you will have to buy two boards, or simply copy the circuit onto smaller boards.

ADC and DAC

The ADC, and DAC, communicates with the Raspberry Pi through the serial peripheral interface (SPI). The SPI connections also exist on the MCP3002 and MCP4802 IC packages.

Where to Buy

Amazon and eBay are currently the best places to purchase these boards. You will find it listed on Google and almost all the major electronics stores sell them.

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