Sense Hat Astro-Pi - the "micro laboratory" ready to use
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The Hat Sense is a remarkable initiative from the project "Astro Pi" and offers an expansion card that embeds a series of sensors ready for use. A real lab waiting for your ideas.
The Hat Sense will be a tool of choice to animate Workshops, courses, interactive experiences, ... to discover the world of electronic hacking and its possibilities on the Raspberry Pi without having to make a connection.
The Hat Sense includes orientation sensors, magnetic, gyroscope, accelerometer, atmospheric pressure, humidity, temperature to perform many experiences, applications, human-machine interfaces and even games as well as an Atmel microcontroller.
You will be able to know the speed of your Pi, its orientation relative to the ground, the humidity rate of the air, the temperature, etc. The "Joystick" allows to interact with your programs.
The Hat also has an 8x8 RGB LED matrix (a display) that allows you to display the data of the different sensors (in the form of scrolling text, graphics or other). With the magnetometer, you could create a compass indicating the magnetic north pole. You could also use the little joystick to make a Tetris, Ping or Snake game.
The Hat Sense is plugged into the GPIO port of the Raspberry-Pi using its 40-pin connector. This allows the Raspberry-Pi to power the Hat Sense and perform the data exchange. Once assembled, all you have to do is download the Python code and you have an "Astro Pi".
Writing programs for the Hat Sense is really very simple. The Hat has a Python library that allows you to start easily and quickly. The possibilities of projects around this Hat are numerous, you can get an idea of the possibilities by visiting the site astro-pi.org (English). You will also find lots of information and ideas.
When you buy this product, you receive a Hat Sense. The Raspberry-Pi, case and other items are not included (only used for illustrative purposes).
Here are some links to some documentation and tutorial around the Hat Sense.
MCHobby invested time and money to offer a "freely accessible" French translation. Thank you for supporting our efforts by purchasing your Sense Hat at MCHobby.
Accelerometer / Gyroscope / Magnetic Field
These sensors have the characteristic of periodic sampling of the sensor values - with internal FIFO storage. The LPS25H and HTS221 have a maximum sampling rate of 25 measurements per second, the LSM9DS1 has a maximum sampling rate of 952Hz - These features would be sufficient (cf this article from the Pi foundation) to consider the birth of quadcopters controlled by Raspberry-Pi.
The LED matrix is based on RGB LEDs equipped with a constant current controller to ensure beautiful colors... even when the voltage varies. LEDs are controlled by an Atmel ATTiny88 microcontroller well known in the Arduino world. The Firmware allows to control 8x8 RGB LEDs with a resolution of 15 bits.
For those who want more details, the AVR firmware is available on the GitGub of the Pi foundation.
The LED matrix is refreshed at the frequency of 80 Hz.
As a bonus, the LED matrix is also recognized as a FrameBuffer device.
You can send data directly to the FrameBuffer. So try the command:
cat /dev/urandom > /dev/fb1
The Atmel microcontroller is responsible for sampling the joystick. The sampling of the joystick is combined with the selection of the lines of of the LED matrix. Therefore, the joystick is also sampled at 80 Hz.
The joystick is also accessible as a standard input device. The different positions of the joystick produce the keyboard inputs Up /Down /Left /Right and Return keyboard.
Atmel ATTiny88 microcontroller
The microcontroller is responsible for controlling the LED matrix and sampling the joystick.
The Atmel SPI bus is connected to the SPI interface of the Raspberry-Pi, so it is possible to reprogram the microcontroller from the Raspberry-Pi (it is also this SPI bus that is used to program the ATTiny 88 during the production phase.
The firmware of the ATTiny88 is interfaced on the I2C bus like other sensors.
I2C bus from Raspberry-Pi
All sensors are connected directly to the I2C bus of your Raspberry-Pi. These sensors are therefore directly accessible from the operating system and Python (as is the case for all other I2C sensors).
The basic firmware of Atmel88 is also accessible on the I2C bus, so you can talk directly with it if you feel like it.
SPI bus from Raspberry-Pi
The SPi bus of the ATTiny88 is connected to the SPI interface of your Raspberry-Pi.
See, above, information about the microcontroller.
Turn off the I2C bus
The good thing about the I2C bus is that you can also connect other I2C devices.
Among the most useful, there is certainly a clock RTC to display the time ;-)
As you will have noticed, the GPIO connector is completely occupied, you can nevertheless recover and extend your I2C bus by welding wires on the following "test points":
Need tension, you will find it here:
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