Robotics is a big part of the raspberry pie and microcontroller communities. Bringing code and electronics together to make an object move is a great motivator for STEM education. Since motors draw far too much current for a typical GPIO pin to handle, we must use a motor controller or driver board to protect the GPIO by allowing the Pico to control a chip on the board.
Kitronik has released two motor control boards for the Raspberry Pi Pico. The $13 (£9) Pico Motor Driver is the smallest board, aimed at basic Pico robotics projects and ideal for students who want to create a fast robot using DC motors and simple sensors. The $18 (£13.20) Pico Robotics Board is larger and comes with many more motor options. This board allows us to control up to eight servo motors, two stepper motors and four DC motors, but we don’t have easy access to the GPIO inputs on the Pico Motor Driver, but for those of us proficient with a soldering iron these can be easily added using from the solder pads underneath where our Pico is located. Both boards come with power inputs for use with batteries/power supplies up to 10.8V. The single power source supplies power to the robot and the Raspberry Pi Pico, simplifying project design.
We tested both boards and built a few test projects to take advantage of the features on both boards.
Design
The larger of the two boards is the Kitronik Pico Robotics board and with the larger size we get more features. Packed into the 2.6 x 2.2 inch (68 x 56 mm) board is a space for the Raspberry Pi Pico, or Pimoroni’s Pico Lipo, along with four motor outputs powered by dual DRV8833 motor drivers. We can use these terminals to drive four DC motors or to drive two stepper motors. On the right side of the board we see eight headers for use with hobby servos like the SG90 or MG90S. The headers communicate directly with the servo via the common pinout signal, voltage, ground (SVG). on the left side of the board is a power input where we can plug in a battery pack and supply up to 10.8V to power the many motors and to power the Raspberry Pi Pico via a built in regulator. We can connect the Pico to the computer and connect to the external power source while there is a diode between the regulator and the 5V pin of the Pico which will prevent accidental damage.
The smaller of the two boards is the Pico Motor Driver board, measuring just 62 x 34mm; This board is designed solely for use with two DC motors through a DRV8833 motor controller. The input power remains the same with a maximum input of 10.8V and a diode to prevent overvoltage from the back-powered Raspberry Pi Pico. What is unique about this board in the Kitronik range is that we have screw terminals for four GPIO pins and 3V, GND which are useful for sensors and inputs to give our robot “vision”. In front of the screw terminals, and printed at the bottom are the GPIO pins used for the terminals, with the exception of the motors abstracted in the Python libraries. The Pico Robotics board does not have a GPIO broken out this way, so there are only labels for the motors. But don’t forget that we can access the GPIO using the solder pads, which are located under the Pico.
Using the Kitronik Pico Robotics Board and Pico Motor Driver
Integrating one of the boards into a chassis is made easier thanks to the mounting holes in the boards. These are used to secure the board to the chassis. If you are 3D printing or laser cutting your own chassis, the position of the mounting holes can be added to the project for a custom fit. If you are using a generic robot chassis, there must be a suitable position.
The Pico Robotics Board is clearly designed for larger, more complex robotics projects, which is evident in the sheer number of motors and servos it can power. It also hides a PCA9685PW IC used to communicate with the board via I2C. The Pico Motor Driver is a simpler board and uses PWM to control the speed of motors.
This means that the MicroPython and CircuitPython libraries are incompatible for both boards, but the syntax of the libraries means that we can transfer code from one board to another by simply switching between the libraries. Please note that the Pico Motor Driver is not compatible with servos and stepper motors.
We tested DC motors, servos and a large stepper motor on the Pico Robotics Board and the only problem we found was determining the pinout of our stepper motor, everything else just worked with minimal effort. Keep in mind that a stepper motor can draw about 1.2 amps at 4V, so your external power source may get a little warm.
The frictionless onboarding process provided by the great hardware is what helps creators focus on building their project. The Pico Motor Driver, while only suitable for DC motor control, is also a frictionless experience, we even made a tutorial on how to build a simple Pico powered robot by using this board and how to use it with a simple switch input.
Our testing centered around the provided MicroPython libraries, but just as we got to the end of the test, we were warned about official CircuitPython libraries for the boards, so we flashed the latest version of CircuitPython to our test board, then copied the correct libraries to the board. The CircuitPython library is almost identical to MicroPython’s, with only the use of utime vs time being a difference. This means that we can transfer our projects from one version of Python to another.
Usage Scenarios for the Kitronik Pico Robotics Board and Pico Motor Driver
Both boards are focused on robotics. The Pico Motor Driver is the best option for those who want to quickly build their first robot. The screw terminals for basic GPIO access are very welcome, more would have been nice, but we have enough for basic projects. The Pico Robotics Board is a much more powerful beast and the plethora of motor options is impressive. If your robot relies on stepper motors or servo motors, this is the board you will naturally gravitate towards.
Another option for GPIO access, which Avram Piltch, editor-in-chief of Mujahid Tricks has tried successfully, is to Pimoroni stackable headers to the Pico, so it has female pins on the top surface that you can connect to jumper wires.
Bottom Line
Whether your robot is big or small, these two boards are just what you need, regardless of your ambitions or skills. The MicroPython and CircuitPython libraries are easy to use and provide an abstracted way to control your robots. From simple DC motor speed controls to high-precision stepper motors, the libraries abstract the complexities and empower makers to create.
The lack of GPIO access on the Pico Robotics board is a shame, since we use I2C there are plenty of GPIO pins that can be broken out for use. The GPIO access on the Pico Motor Driver is great for basic inputs like obstacle sensors, ultrasonic sensors and bump switches, but if you need more, consider getting a stackable header for your Pico. The single power source is fantastic and eliminates the need for two power sources which can be tricky to neatly tuck into a project.