ATtiny13 TinyMoisture

# Overview TinyMoisture monitors the soil moisture of your plants and gives an alarm if you forget to water them again. - Firmware (Github): https://github.com/wagiminator/ATtiny13-TinyMoisture   # Hardware TinyMoisture uses the resistance measurement method to determine the soil moisture. The two probes together with the substrate form a variable resistor. The more humid the soil, the better its conductivity and the lower the electrical resistance. Together with the 10k fixed resistor, a voltage divider is formed. This voltage can be measured by the ADC of the microcontroller. The circuit is based on the [SparkFun Soil Moisture Sensor](https://www.sparkfun.com/products/13322).  # Software ## Implementation The ATtiny13 spends most of its time in sleep mode. Every eight seconds it is woken up by the watchdog timer. It measures the moisture in the soil and compares it with the threshold value selected by the calibration potentiometer. If the soil is too dry, it emits a short acoustic signal via the buzzer and a short optical signal via the LED (ALARM). Then it goes back to sleep mode. The ATtiny can also be woken up by pressing the TEST button (pin change interrupt). An acoustic and optical signal is then output first so that the user can determine whether the battery is still supplying sufficient power. Then measurements of the soil moisture are carried out until the button is released again. In this way, the correct threshold value can be found and set by turning the poti. To avoid corrosion of the electrodes as far as possible, a voltage is only applied during the measurement. The ATtiny is clocked with only 128 kHz and all unused peripherals are switched off so that the power consumption is as low as possible. ```c // Main function int main(void) { // Reset watchdog timer resetWatchdog(); // do this first in case WDT fires // Setup pins DDRB = (1