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Robopoly Shield
This Arduino compatible shield is intended to work with the EPFL Robotics club (Robopoly) robotics platform: the PRismino. It can run on any Arduino as the pin placement is the same. The PRismino library makes it easy to use with shortcut definitions and functions.
It's main purpose is to augment the PRismino's capabilities, Robopoly organises mobile robotics challenges each year and provides all components in a form of disassembled kit including motors and sensors. The H-bridge is one of the most important components as the is allows to build a differential wheeled mobile robot.
Tests have been carried out to see the robustness of the H-bridge, it has an overtemperature shutdown function and short-circuit protection which proved reliable.
Robopoly shield with Bluetooth module installed instead of the DIP-switch.
Characteristics
The shield has various input and output components to expand the PRismino's capabilities:
- Push button, can be used as a regular button (attached to an interrupt pin) or as reset button
- 2 channel DIP-switch
- 2 standard servo motor connections
- SPI port
- Buzzer
- 2 channel H-bridge with connectors (DRV8833)
- Potentiometer, can be disabled by removing a jumper
- I<sup>2</sup>C output with a micromatch connector
- Footprint for a HC-05 Bluetooth module
- 3-pin connector for power from the Robopoly power board
NOTICE: certain components that source current are wired to the micro-controller pins and may damage it if those pins are configured as outputs, please read carefully the PRsimino library documentation to avoid it.
The button can serve as a reset button or an interrupt button.
The DIP-switch shares the same pins as the serial pins, so the Bluetooth module cannot be used when the DIP-switch is used.
There's an absolute maximum rating of 11.8V on the VB input because of the H-bridge.
Electrical schematic and PCB
Assembly
The assembly of the Robopoly shield is documented on the Robopoly's website.
Usage
Refer to the PRsimino library and Bluetooth library for documentation.
The pins 0 and 1 source current, so they shouldn't be used as outputs at any time. Other pins are used for various things but do not put the micro-controller in danger when used as outputs.
| Pin | Function | Comments |
|---|---|---|
A0 | Potentiometer, can be disabled | Protected by a 10K in-line resistor |
A1 | ||
A2 | ||
A3 | ||
A4 | ||
A5 | ||
0 | DIP-Switch/UART RX (Bluetooth) | Do not use as output |
1 | DIP-Switch/UART TX (Bluetooth) | Do not use as output |
2 | I<sup>2</sup>C SDA | Can use internal or external pull-up resistor |
3 | I<sup>2</sup>C SCL | Can use internal or external pull-up resistor |
4 | Bluetooth module AT mode selector | Enters Bluetooth module configuration mode when mounted |
5 | Servo motor | Use S1 in program when addressing the pin |
6 | Servo motor | Use S2 in program when addressing the pin |
7 | Button | Protected by a 10K in-line resistor, use internal pull-up resistor |
8 | Buzzer | Disable via solder jumper to use as input |
9 | H-bridge | Can be used for anything as long as the H-bridge is not used |
10 | H-bridge | Can be used for anything as long as the H-bridge is not used |
11 | H-bridge | Can be used for anything as long as the H-bridge is not used |
12 | H-bridge | Can be used for anything as long as the H-bridge is not used |
13 | LED | Do not use as input as it will consume power |
Component list
The quantity indicates the number of components needed when using the DIP-switch or when using the Bluetooth module. In parenthesis are the 2 10K pull-up resistors for the I<sup>2</sup>C, since the micro-controller has internal pull-up resistors they are optional.
| Part | Reference | Quantity |
|---|---|---|
| PCB | 1 | |
| H-bridge (HTSSOP-16) | DRV8833 | 1 |
| 10uF (minimum) ceramic capacitor | 1 | |
| 10nF, 16V (minimum), X7R, ceramic capacitor | 1 | |
| 2.2uF, 6.3V, 0805 capacitor | 1 | |
| H-bridge connectors | 4UCON-19963 | 2 |
| DIP switch with 2 switches (red) | 4UCON-07236 | 1 |
| SPI 2x3 stackable header | 4UCON-18677 | 1 |
| 10K 0805 resistor | 4(2)/2(2) | |
| 6 pin stackable header (10.5mm) | 4UCON-18688 | 2 |
| 8 pin stackable header (10.5mm) | 4UCON-18689 | 2 |
| Button | 1 | |
| 3 male pins for servo motors | 4UCON-19631 | 2 |
| 3 pin power connector male | 4UCON-19836 | 1 |
| 3 pin power connector female | 4UCON-19841 | 1 |
| Buzzer | 1 | |
| 1K 0805 resistor | 2/5 | |
| Potentiometer 10K | 1 | |
| 2x1 male pins for potentiometer | 4UCON-00795 | 1 |
| Jumper/shunt for potentiometer (6mm, blue) | 4UCON-05726 | 1 |
| Bluetooth module HC-05 | HC-05 | 0/1 |
| 2K 0805 resistor | 0/2 | |
| SMD LED 0805 | 1/2 | |
| Micromatch 4 pin connector | 7-215079-4 | 1 |
CAD files
The CAD file is in Google Sketchup format. Generated with eagleUp, a plugin that exports the board from Eagle CAD and imports it to Google Sketchup.
All additional files needed to generate the board are in the Robopoly Eagle CAD library and SketchUp files project.
Version log
2.0 (2014-07-25)
- Added information about pin usage on silkscreen.
- Added an optional LED on pin 13 since the one on the PRismino is hidden by the shield.
- Replaced potentiometer solder jumper with an actual jumper to free
A0pin for other functions. - Moved button pull-up resistor in series with the line for short-circuit protection, the micro-controller internal pull-up shall be used instead.
- Added a resistor in series with the potentiometer line for short-circuit protection.
- Renamed passive elements silkscreen information in order in which they should be soldered.
- Changed DIP-switch to a 2 channel switch instead of 4.
- Added a stackable SPI header for future module developments.
- The buzzer solder jumper is now connected by default.
- Rounded corners.
- Updated CAD and Gerber files.
- Updated version number and year.
- Added component list.
1.0 (2013-07-09)
- Initial version.
Licence
The Robopoly shield is published under Creative Commons Attribution license.
