09 Software — Pi Setup

The hardware is wired and the relays click on cue. Now get an OS onto the Pi. This page walks Pi Imager (one screen — set the hostname, WiFi, and SSH key, then write the SD card), the first SSH-in over the LAN, and the one-shot setup-pi.sh script that installs every Python dependency, enables I2C, sets up a venv under ~/irrigation/, and wires up the cron schedule. Reboot when prompted, verify with i2cdetect -y 1, and you’re ready for page 10.

ssh [email protected]

The one-shot setup script

The script below installs every Python dependency, enables I2C, creates ~/irrigation/ with a logs/ subdirectory, sets up a Python virtual environment, copies the four irrigation scripts into place, and installs a cron schedule for 7am + 6pm watering checks. Run it once on a fresh Pi OS Lite image; reboot when it tells you to.

#!/bin/bash
# Raspberry Pi Irrigation Controller — Full Setup Script
# Run this on the Pi via SSH or directly
# Usage: bash setup-pi.sh

set -e

echo "============================================"
echo "Irrigation Controller Setup"
echo "============================================"

# 1. Update system
echo "[1/6] Updating system packages..."
sudo apt update && sudo apt upgrade -y

# 2. Install system dependencies
echo "[2/6] Installing system dependencies..."
sudo apt install -y python3-pip python3-smbus i2c-tools python3-venv

# 3. Enable I2C
echo "[3/6] Enabling I2C..."
sudo raspi-config nonint do_i2c 0

# 4. Create project structure
echo "[4/6] Creating project structure..."
mkdir -p ~/irrigation/logs
cd ~/irrigation

# 5. Create virtual environment and install Python packages
echo "[5/6] Setting up Python environment..."
python3 -m venv venv
source venv/bin/activate
pip install adafruit-circuitpython-ads1x15 RPi.GPIO

# 6. Copy scripts (assumes they're in the same directory as this setup script)
echo "[6/6] Installing scripts..."
SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"

for script in irrigate.py calibrate.py status.py manual_water.py; do
    if [ -f "$SCRIPT_DIR/$script" ]; then
        cp "$SCRIPT_DIR/$script" ~/irrigation/
        chmod +x ~/irrigation/$script
        echo "  Installed $script"
    else
        echo "  WARNING: $script not found in $SCRIPT_DIR"
    fi
done

# Create cron wrapper
cat > ~/irrigation/run.sh << 'EOF'
#!/bin/bash
cd ~/irrigation
source venv/bin/activate
python3 irrigate.py
EOF
chmod +x ~/irrigation/run.sh

# Set up cron schedule
echo "Setting up cron schedule..."
(crontab -l 2>/dev/null | grep -v irrigation; echo "0 7 * * * ~/irrigation/run.sh >> ~/irrigation/logs/cron.log 2>&1"; echo "0 18 * * * ~/irrigation/run.sh >> ~/irrigation/logs/cron.log 2>&1") | crontab -

echo ""
echo "============================================"
echo "Setup complete!"
echo "============================================"
echo ""
echo "Next steps:"
echo "  1. Reboot: sudo reboot"
echo "  2. After reboot, verify I2C: sudo i2cdetect -y 1"
echo "  3. Calibrate sensors: cd ~/irrigation && source venv/bin/activate && python3 calibrate.py"
echo "  4. Update thresholds: nano ~/irrigation/irrigate.py"
echo "  5. Test run: python3 ~/irrigation/irrigate.py"

Run it

You need the script and the four irrigation Python files (irrigate.py, calibrate.py, status.py, manual_water.py) on the Pi together in one directory. Either git clone from your fork of the repo, or scp them from your laptop (scp -r irrigation/ [email protected]:~/). Then from the Pi’s SSH session:

cd ~/irrigation
bash setup-pi.sh

The script logs each step ([1/6] through [6/6]); apt update + the Python deps takes 3-5 minutes on a fresh image. The first time it runs raspi-config nonint do_i2c 0 you may see a brief flash about reconfiguring dphys-swapfile — that’s normal.

What the script does, step-by-step

• [1/6] apt update + upgrade — refreshes package lists and applies security patches (the freshest Pi OS image is usually a few weeks old by the time you flash it).
• [2/6] install python3-pip + python3-smbus + i2c-tools + python3-venv — Python 3’s package manager, the smbus library for I2C, the i2cdetect debug tool, and the venv module.
• [3/6] enable I2C — turns on the I2C kernel module via raspi-config nonint do_i2c 0 (the nonint flag means no interactive menu — the script can flip the bit and move on).
• [4/6] create ~/irrigation/ — the project directory, with a logs/ subdirectory for the cron output log.
• [5/6] venv + pip install adafruit-circuitpython-ads1x15 + RPi.GPIO — an isolated Python environment under ~/irrigation/venv/ plus the two libraries irrigate.py imports (the ADS1115 driver for the moisture sensors, and RPi.GPIO for the relay pins).
• [6/6] copy scripts + create cron wrapper + install cron schedule — drops irrigate.py, calibrate.py, status.py, and manual_water.py into ~/irrigation/, creates run.sh (the cron wrapper that activates the venv before running irrigate.py), and installs cron lines for 7am + 6pm watering checks logged to ~/irrigation/logs/cron.log.

After the script finishes you’ll have this layout under ~/irrigation/:

~/irrigation/
├── venv/                       # Python virtual environment (5)
├── logs/
│   └── cron.log                # appended by cron at 7am + 6pm
├── irrigate.py                 # main loop — page 10
├── calibrate.py                # interactive sensor reader — page 11
├── status.py                   # one-shot status print
├── manual_water.py             # manual override CLI
├── run.sh                      # cron wrapper (sources venv, runs irrigate.py)
└── setup-pi.sh                 # this script (kept around for re-runs)

Reboot and verify

The I2C kernel module needs a reboot to load:

sudo reboot

Wait ~30 seconds; SSH back in once the LED activity settles.

ssh [email protected]

Verify I2C is working — you should see 48 in the address grid (the ADS1115’s default I2C address):

sudo i2cdetect -y 1

If 48 shows up, your sensors are reachable from the Pi and you’re ready for page 10. If the grid is empty, one of three things is wrong: the ADS1115 isn’t powered (check 3.3V on its VDD pin), SDA and SCL are swapped at the Pi header (re-check the page-08 wiring table), or the ADDR pin is floating instead of tied to GND. Page 13’s troubleshooting section walks the full I2C debug path.

With the Pi software installed and I2C verified, page 10 walks the irrigation script itself — what each config block in irrigate.py means, how the watering loop decides to fire a zone, and the finally: all_off() fail-safe that guarantees no relay stays latched if the script crashes.