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Add-ons turn Raspberry Pi into robot controller, drone autopilot

Jun 11, 2014  |  Eric Brown
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Mikronaut launched a “RoboPi” robot controller for the Raspberry Pi, while Emlid tapped Indiegogo for its Pi-ready “Navio” shield for drone autopilots.

LinuxGizmos receives tips about Raspberry Pi shields and other add-ons all the time, but relatively few appear to be sufficiently professional to merit coverage. Two new entries that appear to fit that description include a newly shipping Mikronaut RoboPi add-on, and over at Indiegogo, an Emlid Navio shield, aimed at robot control and autopilot applications, respectively.

 
Mikronaut RoboPi

The Raspberry Pi has spawned a variety of robot control add-ons, such as the Roboteq RIO, not to mention a number of full-fledged robot kits like RobotBits.co.uk’s Frindo. Joining the former category is Mikronaut’s RoboPi, which stacks on top of a Raspberry Pi Model A.



RoboPi
(click image to enlarge)

The RoboPi board is based on Mikronaut’s RoboProp robot controller board for Arduino or Dagu Mr. Basic platforms. It can run RoboProp software that does not require the RoboProp’s L298 motor driver or microSD slot, says the company.

Like the RoboProp, the RoboPi is built around an eight-core, 32-bit Parallax Propeller P8X32 microcontroller, which offloads hard real-time I/O and enables more precise timing than is possible on the Pi alone. The RISC processor runs at 100MHz, and provides up to 25 MIPS of processing power. You can choose between a 256Kb or 512Kb boot EEPROM.



RoboPi with Pi (left) and also with EZasPi prototyping boards
(click images to enlarge)

The RoboPi connects to the Pi via three 10-pin connectors, and offers 24 servo-compatible headers, as well as eight servo-compatible headers for an eight channel 0-5V ADC. There’s also 4-pin I2C expansion headers for the Pi and the Propeller chip respectively.

A screw terminal provides external power for most of the servo connectors, while an onboard voltage regulator provides 3.3V with power on LED from the 5V on the Pi header, says Mikronaut. The RoboPi is designed to stack directly on top of the Pi, but is also available with EZasPi prototyping boards that separate the boards for development.



Robot driven by RoboPi with Pi
(click image to enlarge)

The RoboPi is available in the standard, full $50 kit, or a $25 “Lite” kit that is missing the P8X32 MCU and two ICs. Both kits require board assembly, but a $100 version gives you the fully assembled board, minus the Pi.

 
Emlid Navio

Autopilots for drones and other mobile robots can range into the thousands of dollars, such as the Linux-based os-Series autopilot computers from Airware. However, other solutions are appearing with less rigorous requirements aimed at smaller craft.



Navio with Pi
(click image to enlarge)

Emlid’s Navio turns the Raspberry Pi into an autopilot for drones, cars, boats, submarines, multi-rotors, planes, and other mobile robots, says the company. It incorporates inertial measurement unit (IMU), GPS, a barometric altimeter, and servo control. The Pi, meanwhile, contributes computer vision, HD video streaming, and other capabilities, notes Emlid.

The project already won its Indiegogo funding, but is now in a stretch funding phase. Emlid aims to use the stretch funds for adding non-volatile FRAM storage.

That means you can still get the Navio autopilot board at the funding price of $145, or $195 for a Navio Raw version with a higher-end U-blox NEO-6T GPS radio. The latter incorporates raw data that that can be used for real-time kinematics (RTK) processing. The standard Navio board has a U-blox NEO-7M multi-GPS/GNSS/GLONASS receiver.



Side view of Navio with Pi

 
Aside from the GPS/GNSS devices, other components include an InvenSense MPU-9250 IMU, which uses accelerometers, gyroscopes, and magnetometers for orientation. There’s also an Amsys MS5611 barometer and temperature measurement module, which provides high precision pressure sensing, as well as a linear pressure measurement element (pressure die), and a low-power 24 bit ADC.

Additional Navio elements include an NXP Semiconductor PCA9685 PWM generator for serving up to 13 servos. An RC input port connects PPM or S.Bus receivers for manual control. There’s also an ADC for battery monitoring, and some DF13 headers for UART, SPI, and I2C extensions.



Drone with Navio and Pi
(click image to enlarge)

The Navio shield will also be made available for the Banana Pi and HummingBoard Pi clones. Emlid notes, however, that because the Banana Pi places its 26-pin header slightly closer to the RCA connector that does the Raspberry Pi, a proper fit will require some desoldering.

 
Further information

The Mikronaut RoboPi is available now, starting with a stripped-down Lite kit without chips, selling for $25, a full $50 kit, or a $100 pre-assembled version. All prices are minus the Raspberry Pi SBC. More information may be found at Mikronaut’s RoboPi page.

Emlid’s Navio is available for Indiegogo funding at packages starting at $145, shipping in July, or $195 for a Navio Raw version with an advanced GPS with raw data, shipping in August. Once again, prices do not include the Pi. More information may be found at the Navio Indiegogo page or this Emlid blog page.
 

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