The Gertboard extends the usefulness of the Pi by allowing a variety of devices to be connected to the Pi, and, thus be controlled by the Pi. It is made up of individual circuits that have connector pins at their inputs and outputs. These circuits are connected to each other, to the Pi's GPIO pins, or to external devices. Jumpers are used to connect adjacent connector pins, and wires, with a socket on each end are used for other connections. Please note the colored wires in the photo above.
The Gertboard is available from SparkFun for $53 (USD). Newark Electronics has it for $50. Adafruit does not seem to carry it.
As is usual with most things you buy for the Pi (and the Pi, itself) the Gertboard does not come with any documentation. Yes, it ships with a CD, but that is simply a marketing tool to sell ARM development software. There is, however, a very comprehensive user's manual that explains every circuit. All circuits have at least one test routine. The manual shows how to connect the circuits for each test and explains the test software. The test software, in C++ and Python must be downloaded to the Pi. The manual details how to get, and install that software. Even though the user's manual references the schematic diagram for the board, these schematics are not included in the manual. However, these schematics are available as a separate file. The best way to get both the user's manual and the schematics is from the SparkFun page. So click here.
So what are the features of the Gertboard?
- The Gertboard plugs onto the GPIO connector of the Pi. Because the Gertboard's GPIO bottom facing connector socket connects directly to the top facing pins of the Pi's connector, it forms a single, physically stable, unit consisting of the two devices (see note below).
- Twelve buffers for inputs to the Pi and twelve buffers to drive outputs from the Pi. Input buffers protect the Pi from inputs like sensors while output buffers reduce the loading of the Pi by output devices (like LEDs).
- 12 LEDs
- 3 Momentary push button switches
- 6 High Voltage/High Current Outputs (open collector drivers). Each of these circuits can drive half an amp at 50 volts
- A fused motor controller. Uses the pulse width modulation (PWM) capabilities of the Pi to control the speed and turning direction of the motor. This circuit can drive 2A at 18V.
- Two 8 bit digital to analog (D to A) circuits.
- Two 10 bit analog to digital (A to D) circuits.
- And best of all an Atmel ATmega328 microcontroller IC. This is the same microcontroller as used by Arduino boards. Gordon Henderson, of Drogon Systems has developed all of the methods and procedures to interface the microcontroller to the Pi. The instructions to obtain all of the software, including the Arduino IDE (Integrated Development Environment) are provided by Gordon. To write programs (in C++) on the Pi for the Atmega328, and to get those programs loaded in the Atmega328, you use the Arduino IDE running on the Pi. The Gertboard User Manual provides the link to Gordon's web page. The Arduino IDE provides many sample programs and C++ help to get you started.
- Prototyping area (outlined in blue in the figure above) to wire in your own circuitry. You will see where I use this area in my next blog post.
I have version 2 of the Gertboard. As I mentioned above, the Gertboard and the Pi connect directly together. This is not true for version 1. Version 1 requires a ribbon cable to connect to the Pi. I believe only Version 2 is available now. Version 1 came as a kit requiring the purchaser to assemble and solder parts to the board. Version 2 cones completely assembled. Version 1 used thru-hole parts with all IC's in sockets. Version 2 uses mostly surface mounted parts. In version 2, most IC's are thru-hole but only one IC, the ATmega microcontroller is in a socket. The other ICs are soldered to the PC board.
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