When I first started making AVR modules, there was no Raspberry Pi or ESP8266. Arduino was introduced in 2005, the same year I started with the AVR microcontroller. But I didn’t know of it until many years later.

There weren’t any Wi-Fi enabled microcontrollers at that time. Both Ethernet and Bluetooth interfaces were more expensive, and harder to interface. So I ended up using the good old serial port.

I made my first module with a serial interface in 2007. RS-232 was cheap, and easy to implement.

With RS-232 I got a way of getting data between the microcontrollers and the computer, but I still needed a defined syntax. So I set out to make one, and called it SIOS — Serial Input/Output System.

AVR is a series of microcontrollers from Atmel. Fitted with A/D converters, comparators, timers, interrupts, internal oscillator, and more. Flash memory is used for the main program, SDRAM for variables and EEPROM for values that need to be saved through a power loss. Cheap, fast and easy make them perfect for home automation projects.

Temperature sensor with serial RS-485 interface. Two additional sensors can be connected using 3-pin headers on the circuit board. Uses an AVR ATmega8 microcontroller.

I rebuilt an existing interface module — to be a stand-alone temperature and humidity sensor, with serial RS-232 interface. Uses an AVR ATmega8 microcontroller.

I rebuilt an existing interface module — to be a stand-alone temperature and light sensor, with serial RS-232 interface and some signal LEDs. Uses an AVR ATmega8 microcontroller.