Tiny Tapeout > Tiny Tapeout Chips > Tiny Tapeout SKY 26b > 896 IEEE Open-Silicon 2026 x NITHUB: Soil Moisture Irrigation Controller
896 IEEE Open-Silicon 2026 x NITHUB: Soil Moisture Irrigation Controller
896 : IEEE Open-Silicon 2026 x NITHUB: Soil Moisture Irrigation Controller
- Author: Shadia, Elijah, Oluwatomiwa, Emmanuel, Daniel, Orobosa
- Description: An IEEE Division 1 Open Silicon Tapeout Initiative Project, this is a finite state machine that controls irrigation pump based on soil moisture levels detected by two comparators, with error handling for invalid states
- GitHub repository
- Open in 3D viewer
- Clock: 10000000 Hz
About this project
This is a project based on the IEEE Division 1 Open Silicon Tapeout Initiative
How it works
This is a project based on the IEEE Division 1 Open Silicon Tapeout Initiative
The Soil Moisture Irrigation Controller is a finite state machine (FSM) that automatically controls an irrigation pump based on soil moisture levels. It uses two comparators to detect moisture levels:
- COMP0 and COMP1: Inputs from comparators that compare soil moisture voltage against two reference thresholds (Vref_low and Vref_high)
- Moisture levels:
- 00: Dry soil (V < Vref_low) → IRRIGATE state
- 01: Mild soil (Vref_low < V < Vref_high) → IDLE state
- 11: Wet soil (V > Vref_high) → SATURATED state
- 10: Invalid comparator state → INVALID state (error condition)
The FSM has four states:
- IDLE: Pump off, waiting for dry conditions
- IRRIGATE: Pump on, watering the soil
- SATURATED: Pump off, soil is too wet
- INVALID: Error state, pump off, invalid_flag asserted
The system transitions between states based on moisture readings, ensuring efficient water usage and preventing over/under watering.
How to test
- Setup: Connect moisture sensor to comparators, comparators to COMP0/COMP1 inputs, pump to PUMP output
- Power on: Apply clock (CLK) and reset (RST) to initialize to IDLE state
- Monitor moisture:
- Dry soil (COMP1=0, COMP0=0): Should enter IRRIGATE state (PUMP=1)
- Mild soil (COMP1=0, COMP0=1): Should enter IDLE state (PUMP=0)
- Wet soil (COMP1=1, COMP0=1): Should enter SATURATED state (PUMP=0)
- Invalid (COMP1=1, COMP0=0): Should enter INVALID state (INVALID_FLAG=1, PUMP=0)
- Reset: Assert RST to return to IDLE state
External hardware
- Moisture sensor: Soil moisture sensor that outputs analog voltage proportional to soil wetness
- Two comparators: LM393 or similar, configured with Vref_low and Vref_high thresholds
- Irrigation pump: Relay-controlled water pump connected to PUMP output
- Clock source: External clock generator (1MHz recommended)
- Power supply: 3.3V or 5V depending on Tiny Tapeout board
Pin Descriptions
Inputs
- CLK: System clock input
- RST: Synchronous reset (active high)
- COMP0: Comparator 0 output (low threshold)
- COMP1: Comparator 1 output (high threshold)
Outputs
- PUMP: Irrigation pump control (1 = on, 0 = off)
- INVALID_FLAG: Error indicator (1 = invalid moisture reading)
Timing
- Clock frequency: 1MHz
- State transitions occur on rising clock edge
- Reset is synchronous
IO
| # | Input | Output | Bidirectional |
|---|---|---|---|
| 0 | COMP0 | PUMP | |
| 1 | COMP1 | INVALID_FLAG | |
| 2 | |||
| 3 | |||
| 4 | |||
| 5 | |||
| 6 | |||
| 7 |