Introduction to Home Automation with Raspberry Pi and Fhem

Home Automation is a cool subject - Its futurity, energy efficient, everything is everywhere under control and at least its a little bit nerdy/geeky. So concerning sizing, power and pricing the Raspberry Pi is qualified for an house-controller. The additional hard- and software requirements can be achieved by already existing hardware modules and open source software - the setup itself is no rocket science.

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Raspberry Pi Caller and Answering Machine

For some purposes i thought it would be very nice to enable some telecommunication abilities on raspberry pi. For example if something does not work as it should (e.g. average load too high, temperature/humidity too high) raspberry pi can call you. Or if you just want to control something quickly via phone (e.g. starting a process, reboot or open the door) - raspberry pi can answer your calls and made it for you. Of course you can make it via SMS or web-interface, too - but for example a call often gets more attention than a sms.

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Raspberry Pi Watchdog Timer

Since i’m familiar with using a watchdog timer in some microcontroller-projects, i’ve been thinking about watchdog-support for Raspberry Pi. Generally a watchdog timer is nothing else than a timer-register which can be realized on hardware- and/or software-side. It’s main purpose is to trigger a system reset or other corrective action if something doesn’t works anymore as it should be. In detail the timer-register needs to get resetted in a functional workflow before its filled up and triggers the reset or special action.

This means that the functional system must trigger a heartbeat to the watchdog ("feeding the dog") within a hard (hardware, not changeable) or soft (software, self-definable) time period. An absence of some heartbeats results in reaching the time limit and triggering the reset/action.

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Raspberry Pi with I2C-Arduino-Slave

Since Raspberry Pi has only about 8 GPIO’s (or up to 17 if you reconfigure UART, SPI and I2C as GPIO) or for some other reasons, it may be helpful to combine Raspberry Pi with another μC or PIC (or even a ready-to-use μC-/PIC-Board like Arduino, Netduino or Pinguino) e.g. to get more I/O’s or just to seperate two different application areas. Such a combination is surely easy to setup via serial or usb - but at least if serial/usb is already in use or if you are thinking about using more than one further μC or PIC its getting a bit clumsy. Much more flexible and cleaner will be a solution via I2C - in this case you can easily address up to 128 slaves.

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I2C-Level-Shifter / I2C-Bridge

For some scenarios you need to enable communication over two or more different voltage levels. For example, if you want to use an ATmega168/328 or Arduino running @ 16MHz/5V as an i2c-slave with a RaspberryPi running @ 3V3 you need to shift/translate/isolate intercommunication levels between both devices. (Remember that RaspberryPi only runs 3V3 logic levels and a higher voltage may destroy the board.)

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Raspberry Pi and I2C

I2C (Inter-Integrated Circuit) (see wikipedia), also known as two-wire interface
(TWI), is a very handy bus protocol. It enables communication of multiple devices over just two wires: SCL (clock line) and SDA (data line).

Generally the RPi supports I2C over GPIO assumed that the kernel supports it and a driver is loaded. For this requirement i use the kernel of Chris Boot which is based on a 3.2 kernel, supports SPI and I2C out of the box and has some more features and advantages in comparison to the official RPi 3.1 kernel.

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Raspberry Pi Fritzing Part

For doing some prototyping stuff it maybe really helpfull to use Raspberry Pi within’ Fritzing*. Since i haven’t found a part of the board until today i’ve spent some time and created the svg-files for building the appropriate part of the board, model b.

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PCD8544 Library for Raspberry Pi

(Nokia 3310/5110 Display)

For some Arduino/ATmega328p/µC-based projects i’ve used a PCD8544-based Nokia 3310/5110 Display. The main advantages of this display are the low price and the simplicity of driving it. So since i’ve got my first Raspberry Pi and discovered the GPIO-functionality i wanted to drive this display with my RPi.

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