Camera Snapshots with Python

SiliconWit.IO treats cameras as standard devices: you upload a JPEG or PNG via HTTP, get back a URL, and include that URL in your telemetry payload. The dashboard then renders the image as a clickable thumbnail alongside your sensor data.

This tutorial walks through the entire process: creating a device, configuring data fields, writing a Python script that generates and uploads snapshots with telemetry, and running it on hardware as small as a Raspberry Pi Zero.

What You Will Build

• Snapshot Upload - HTTP POST images directly from your device to SiliconWit.IO’s snapshot endpoint, no MQTT broker needed
• Paired Telemetry - every snapshot arrives with its corresponding sensor readings; no orphaned images, no data without visual evidence
• Dashboard Thumbnails - any telemetry field ending in _url is automatically rendered as a clickable thumbnail
• Pi Zero Compatible - only requires requests and Pillow; runs comfortably on a Raspberry Pi Zero W or Zero 2W

Prerequisites

• A SiliconWit.IO account (free tier works, 10 snapshots/day)
• Python 3.7+ with pip
• Internet connectivity on your device

Step 1: Create the Device

1. Log in to siliconwit.io and navigate to Devices in the dashboard.

2. Click “Add Device” and fill in the following:

   Field	Value	Why
   Name	Field Sensor Cam	Descriptive name shown on your dashboard
   Type	Sensor	The device captures and sends data
   Data Direction	Send Only	We only upload data from the device
   Connectivity	WiFi + HTTP or 4G/LTE + HTTP	We use HTTP POST for both snapshots and telemetry
   Data Interval	5 minutes	How often the device sends readings (adjust to your needs)
   Schema Mode	Strict	Default for free plan, only declared fields are accepted

3. Enable Camera Snapshots - check the box labelled “Allow this device to upload images via HTTP POST.”

4. Configure Data Fields - you can either add them manually or use the JSON import tool (see Step 2).

5. Click “Create Device” - the system generates your Device ID and Access Token.

Caution

Save your Access Token immediately! It is only shown once. Copy it somewhere safe before closing the dialog.

Step 2: Configure Data Fields

Your device needs five fields: four sensor readings plus a snapshot URL. The free plan allows up to 5 fields.

Option A: Import from JSON

Save this file as field-sensor-cam-fields.json:

[
  { "name": "temperature", "label": "Temperature", "unit": "°C" },
  { "name": "humidity", "label": "Humidity", "unit": "%" },
  { "name": "soil_moisture", "label": "Soil Moisture", "unit": "%" },
  { "name": "light", "label": "Light", "unit": "lux" },
  { "name": "snapshot_url", "label": "Snapshot", "unit": "" }
]

Then in the device creation form, click Import and browse to the file.

Option B: Add Manually

Add each field one by one using the form:

Name	Label	Unit
temperature	Temperature	°C
humidity	Humidity	%
soil_moisture	Soil Moisture	%
light	Light	lux
snapshot_url	Snapshot	(leave empty)

Tip

Why snapshot_url? SiliconWit.IO automatically detects any field ending in _url that points to an image and renders it as a clickable thumbnail in the dashboard. No extra configuration needed.

Step 3: Understand the API

Two HTTP endpoints work together to pair snapshots with telemetry.

Snapshot Upload

POST /api/devices/{device_id}/snapshot

Header	Value
Authorization	Bearer YOUR_ACCESS_TOKEN
Content-Type	image/jpeg or image/png

Body: Raw image bytes (max 500 KB)

Response (200):

{
  "success": true,
  "url": "/api/devices/{device_id}/snapshot/{id}",
  "id": "a1b2c3d4-..."
}

Telemetry Ingestion

POST /api/devices/ingest

Body (JSON):

{
  "device_id": "YOUR_DEVICE_ID",
  "access_token": "YOUR_ACCESS_TOKEN",
  "data": {
    "temperature": 28.3,
    "humidity": 65.0,
    "soil_moisture": 42.5,
    "light": 720,
    "snapshot_url": "https://siliconwit.io/api/devices/.../snapshot/..."
  }
}

Response (200):

{ "success": true }

Error Codes

Status	Meaning
400	Missing device ID or unsupported content type
401	Invalid access token
403	Device is paused
413	Image exceeds 500 KB limit
429	Daily snapshot quota exhausted
503	Storage temporarily unavailable

Plan Limits

Plan	Snapshots/Day	Retention
Free	10	7 days
Starter	50	30 days
Business	200	365 days

Step 4: Install Dependencies

pip:

pip install requests Pillow

Raspberry Pi OS:

sudo apt update
sudo apt install python3-pip python3-pil
pip3 install requests

Requirements file - create requirements.txt:

requests
Pillow

Then:

pip install -r requirements.txt

Step 5: The Python Script

Create a file called field-sensor-cam.py. This script is fully self-contained - it generates its own realistic field images and sensor data with no external downloads required.

Caution

Replace the credentials: Update DEVICE_ID and ACCESS_TOKEN with the values from Step 1.

"""
Field Sensor Cam - generates realistic field images and sensor data,
uploads snapshot + telemetry atomically to SiliconWit.IO via HTTP.

No external data sources - fully self-contained.
"""
import io
import json
import math
import random
import requests
from datetime import datetime
from PIL import Image, ImageDraw

# --- Config: replace with your device credentials ---
DEVICE_ID = "YOUR_DEVICE_ID"
ACCESS_TOKEN = "YOUR_ACCESS_TOKEN"
BASE_URL = "https://siliconwit.io"
INGEST_URL = f"{BASE_URL}/api/devices/ingest"
# --- End config ---

# Crop profiles with realistic parameter ranges
CROP_PROFILES = [
    {"crop": "Tomato",  "temp": (22, 32), "hum": (55, 75),
     "soil": (40, 65),  "light": (500, 850)},
    {"crop": "Corn",    "temp": (20, 30), "hum": (50, 70),
     "soil": (45, 70),  "light": (600, 900)},
    {"crop": "Rice",    "temp": (24, 35), "hum": (70, 90),
     "soil": (70, 95),  "light": (400, 750)},
    {"crop": "Wheat",   "temp": (12, 24), "hum": (40, 60),
     "soil": (30, 55),  "light": (450, 800)},
    {"crop": "Potato",  "temp": (15, 22), "hum": (60, 80),
     "soil": (50, 75),  "light": (350, 650)},
    {"crop": "Grape",   "temp": (18, 30), "hum": (45, 65),
     "soil": (25, 45),  "light": (550, 900)},
    {"crop": "Coffee",  "temp": (18, 26), "hum": (60, 85),
     "soil": (45, 65),  "light": (200, 500)},
    {"crop": "Mango",   "temp": (26, 38), "hum": (50, 75),
     "soil": (30, 55),  "light": (600, 900)},
]


def generate_readings():
    """Generate realistic varied sensor data from a random crop profile."""
    profile = random.choice(CROP_PROFILES)
    t_lo, t_hi = profile["temp"]
    h_lo, h_hi = profile["hum"]
    s_lo, s_hi = profile["soil"]
    l_lo, l_hi = profile["light"]

    # Time-of-day influence on readings
    hour = datetime.now().hour + random.uniform(-2, 2)
    day_factor = max(0, math.sin(math.pi * hour / 24))

    temp = round(random.uniform(t_lo, t_hi) + day_factor * 4 - 2, 1)
    humidity = round(random.uniform(h_lo, h_hi) - day_factor * 10, 1)
    soil = round(random.uniform(s_lo, s_hi) - day_factor * 5, 1)
    light = int(random.uniform(l_lo, l_hi) * day_factor)

    return {
        "temperature": max(t_lo - 3, min(t_hi + 5, temp)),
        "humidity": max(20, min(99, humidity)),
        "soil_moisture": max(5, min(99, soil)),
        "light": max(0, light),
    }, profile["crop"]


def generate_scene(crop_name, readings):
    """Generate a field scene image that visually reflects the readings."""
    WIDTH, HEIGHT = 640, 480
    img = Image.new("RGB", (WIDTH, HEIGHT))
    draw = ImageDraw.Draw(img)

    temp = readings["temperature"]
    humidity = readings["humidity"]
    light = readings["light"]
    soil = readings["soil_moisture"]

    # Sky colour based on light level
    if light > 500:
        sky_top, sky_bot = (90, 160, 230), (160, 200, 240)
    elif light > 200:
        sky_top, sky_bot = (140, 150, 170), (180, 185, 195)
    elif light > 50:
        sky_top, sky_bot = (60, 50, 90), (200, 140, 100)
    else:
        sky_top, sky_bot = (15, 15, 40), (30, 30, 55)

    horizon = int(HEIGHT * 0.50)
    for y in range(horizon):
        t = y / horizon
        r = int(sky_top[0] + (sky_bot[0] - sky_top[0]) * t)
        g = int(sky_top[1] + (sky_bot[1] - sky_top[1]) * t)
        b = int(sky_top[2] + (sky_bot[2] - sky_top[2]) * t)
        draw.line([(0, y), (WIDTH, y)], fill=(r, g, b))

    # Sun or moon
    if light > 200:
        sx = random.randint(80, WIDTH - 80)
        sy = random.randint(30, horizon - 60)
        sr = 25 + int(light / 100)
        brt = min(255, 180 + int(light / 5))
        draw.ellipse([sx - sr, sy - sr, sx + sr, sy + sr],
                     fill=(brt, brt - 20, min(255, int(brt * 0.5))))
    elif light < 50:
        draw.ellipse([480, 35, 515, 70], fill=(180, 180, 200))

    # Clouds - more clouds when humidity is higher
    for _ in range(int(humidity / 15)):
        cx = random.randint(30, WIDTH - 30)
        cy = random.randint(20, horizon - 40)
        cb = 230 if light > 200 else 80
        for dx, dy in [(-22, 0), (0, -10), (22, 0), (12, 6), (-12, 6)]:
            cr = random.randint(14, 26)
            draw.ellipse([cx+dx-cr, cy+dy-cr, cx+dx+cr, cy+dy+cr],
                         fill=(cb, cb, cb + 10))

    # Ground - darker when soil is wetter
    dry = max(0, min(1, 1 - soil / 100))
    for y in range(horizon, HEIGHT):
        t = (y - horizon) / (HEIGHT - horizon)
        r = int((90 - 40 * dry) - 30 * t)
        g = int((130 + 20 * dry) - 50 * t)
        b = int((50 + 15 * dry) - 20 * t)
        draw.line([(0, y), (WIDTH, y)],
                  fill=(max(0, r), max(0, g), max(0, b)))

    # Wet patches on soil
    if soil > 50:
        for _ in range(int(soil / 10)):
            px = random.randint(0, WIDTH)
            py = random.randint(horizon + 20, HEIGHT - 10)
            pr = random.randint(10, 30)
            draw.ellipse([px-pr, py-pr//2, px+pr, py+pr//2],
                         fill=(40, 60, 30))

    # Crop-specific plant colours
    crop_colors = {
        "Tomato": {"stem": (40, 100, 20), "fruit": (200, 50, 30)},
        "Corn":   {"stem": (50, 140, 30), "fruit": (220, 200, 60)},
        "Rice":   {"stem": (80, 160, 50), "fruit": None},
        "Wheat":  {"stem": (180, 170, 60), "fruit": (200, 180, 70)},
        "Potato": {"stem": (50, 120, 35), "fruit": None},
        "Grape":  {"stem": (60, 110, 40), "fruit": (100, 30, 120)},
        "Coffee": {"stem": (30, 90, 25),  "fruit": (140, 50, 30)},
        "Mango":  {"stem": (40, 120, 30), "fruit": (240, 180, 40)},
    }
    colors = crop_colors.get(crop_name,
                             {"stem": (50, 130, 30), "fruit": None})

    # Plant height reflects temperature and soil moisture
    health = min(1.0, (temp / 30) * 0.5 + (soil / 100) * 0.5)
    base_h = int(20 + 30 * health)

    for row_y in range(horizon + 15, HEIGHT, 28):
        for x in range(15, WIDTH - 15, random.randint(28, 42)):
            h = random.randint(base_h - 8, base_h + 12)
            w = random.randint(8, 16)
            gv = random.randint(-20, 20)
            stem = tuple(max(0, min(255, c + gv))
                         for c in colors["stem"])
            draw.polygon([(x, row_y), (x+w//2, row_y-h), (x+w, row_y)],
                         fill=stem)
            draw.line([(x+w//2, row_y), (x+w//2, row_y-h+3)],
                      fill=tuple(max(0, c-30) for c in stem), width=1)
            if colors["fruit"] and random.random() < 0.4:
                fr = random.randint(3, 6)
                fx = x + w//2 + random.randint(-5, 5)
                fy = row_y - h + random.randint(5, h // 2)
                fc = tuple(max(0, min(255, c + random.randint(-20, 20)))
                           for c in colors["fruit"])
                draw.ellipse([fx-fr, fy-fr, fx+fr, fy+fr], fill=fc)

    buf = io.BytesIO()
    img.save(buf, "JPEG", quality=85)
    return buf.getvalue()


def upload_snapshot(image_data):
    """Upload snapshot via HTTP POST, return the full URL."""
    url = f"{BASE_URL}/api/devices/{DEVICE_ID}/snapshot"
    r = requests.post(url, data=image_data, headers={
        "Authorization": f"Bearer {ACCESS_TOKEN}",
        "Content-Type": "image/jpeg",
    })
    r.raise_for_status()
    return f"{BASE_URL}{r.json()['url']}"


def publish_telemetry(readings):
    """Send telemetry via HTTP POST. Returns True on success."""
    r = requests.post(INGEST_URL, json={
        "device_id": DEVICE_ID,
        "access_token": ACCESS_TOKEN,
        "data": readings,
    }, timeout=10)
    if r.status_code == 200:
        return True
    print(f"  HTTP {r.status_code}: {r.text}")
    return False


def main():
    print("=" * 50)
    print("  Field Sensor Cam - SiliconWit.IO")
    print("=" * 50)

    # 1. Generate sensor readings
    print("\n[1/3] Generating sensor data...")
    readings, crop = generate_readings()
    print(f"      Crop: {crop}")
    for key, val in readings.items():
        print(f"      {key}: {val}")

    # 2. Generate a matching scene image
    print("[2/3] Generating field scene...")
    image_data = generate_scene(crop, readings)
    print(f"      {len(image_data)} bytes")

    # 3. Upload snapshot, then publish telemetry
    print("[3/3] Sending snapshot + telemetry...")
    try:
        snapshot_url = upload_snapshot(image_data)
        print(f"      Snapshot: {snapshot_url}")
    except Exception as e:
        print(f"      Snapshot upload failed: {e}")
        return

    readings["snapshot_url"] = snapshot_url
    if publish_telemetry(readings):
        print("      Telemetry: published")
    else:
        print("      Telemetry FAILED")
        return

    print(f"\nDone - {crop} field snapshot + data linked.")


if __name__ == "__main__":
    main()

How It Works

1. Generate readings - a random crop profile is selected (Tomato, Corn, Rice, etc.) and realistic sensor values are produced within that crop’s range, influenced by time of day.

2. Generate image - a 640x480 field scene is drawn using Pillow. The scene visually reflects the readings: brighter sky when light is high, more clouds when humidity is high, darker soil when moisture is high, and taller plants when conditions are good.

3. Upload snapshot - the JPEG is POSTed to /api/devices/{id}/snapshot. If this fails, the script stops (no orphaned data).

4. Publish telemetry - the sensor readings plus the snapshot_url are sent to /api/devices/ingest. The dashboard links them together.

Atomicity

If the snapshot upload succeeds but telemetry fails, you will have an orphaned image. The script uploads the snapshot first (the more reliable step) and publishes telemetry immediately after. For production use, consider adding a retry loop around the telemetry call.

Step 6: Run It

python field-sensor-cam.py

Expected output:

==================================================
  Field Sensor Cam - SiliconWit.IO
==================================================

[1/3] Generating sensor data...
      Crop: Rice
      temperature: 33.5
      humidity: 67.0
      soil_moisture: 84.0
      light: 542
[2/3] Generating field scene...
      43718 bytes
[3/3] Sending snapshot + telemetry...
      Snapshot: https://siliconwit.io/api/devices/.../snapshot/...
      Telemetry: published

Done - Rice field snapshot + data linked.

Run it multiple times: each run picks a different crop with different readings, so your dashboard will show varied data with distinct images.

Step 7: Verify on the Dashboard

Navigate to your device’s detail page on siliconwit.io. You should see:

• Data table - each row shows Temperature, Humidity, Soil Moisture, Light, and a Snapshot thumbnail
• Snapshots tab - all uploaded images in a gallery view
• Charts - sensor readings plotted over time

Every data row should have a corresponding snapshot thumbnail. If you see images without data or data without images, check the Troubleshooting section.

Running on a Raspberry Pi Zero

The script is designed to run on constrained hardware. Here is a typical setup for a Raspberry Pi Zero W or Zero 2W.

Hardware Requirements

Component	Purpose
Raspberry Pi Zero W / 2W	Compute + WiFi
Camera Module (v2 or HQ)	Capture real images
DHT22 or BME280 sensor	Temperature + humidity
Capacitive soil moisture sensor	Soil readings
BH1750 light sensor	Lux measurement
5V power supply or battery pack	Power

Adapting for Real Sensors

Replace generate_readings() and generate_scene() with real hardware reads.

PiCamera capture:

from picamera2 import Picamera2
import io

def capture_image():
    """Capture a JPEG from the Pi camera."""
    cam = Picamera2()
    config = cam.create_still_configuration(
        main={"size": (640, 480)}
    )
    cam.configure(config)
    cam.start()
    buf = io.BytesIO()
    cam.capture_file(buf, format="jpeg")
    cam.stop()
    return buf.getvalue()

DHT22 sensor:

import adafruit_dht
import board

dht = adafruit_dht.DHT22(board.D4)

def read_dht():
    """Read temperature and humidity from DHT22."""
    return {
        "temperature": round(dht.temperature, 1),
        "humidity": round(dht.humidity, 1),
    }

Soil moisture + light:

import board, busio
import adafruit_ads1x15.ads1115 as ADS
from adafruit_ads1x15.analog_in import AnalogIn
import adafruit_bh1750

i2c = busio.I2C(board.SCL, board.SDA)

# Soil moisture via ADS1115 ADC
ads = ADS.ADS1115(i2c)
soil_chan = AnalogIn(ads, ADS.P0)

# Light via BH1750
bh = adafruit_bh1750.BH1750(i2c)

def read_soil_and_light():
    raw = soil_chan.value
    soil_pct = round((1 - raw / 26000) * 100, 1)
    return {
        "soil_moisture": max(0, min(100, soil_pct)),
        "light": round(bh.lux),
    }

Running on a Schedule

Use cron to run the script every 5 minutes (matching the data interval configured on the device):

crontab -e

Add this line:

*/5 * * * * /usr/bin/python3 /home/pi/field-sensor-cam.py >> /home/pi/sensor-cam.log 2>&1

Quick Test with curl

If you want to test the snapshot endpoint without Python, use curl:

# Upload a snapshot
curl -X POST "https://siliconwit.io/api/devices/YOUR_DEVICE_ID/snapshot" \
  -H "Authorization: Bearer YOUR_ACCESS_TOKEN" \
  -H "Content-Type: image/jpeg" \
  --data-binary @photo.jpg

# Send telemetry
curl -X POST "https://siliconwit.io/api/devices/ingest" \
  -H "Content-Type: application/json" \
  -d '{
    "device_id": "YOUR_DEVICE_ID",
    "access_token": "YOUR_ACCESS_TOKEN",
    "data": {
      "temperature": 28.3,
      "humidity": 65.0,
      "snapshot_url": "URL_FROM_SNAPSHOT_RESPONSE"
    }
  }'

Troubleshooting

Images appear without data (or vice versa)

Cause: The snapshot upload and telemetry are two separate HTTP calls. If one fails, the other may still succeed.

Fix: The script uploads the snapshot first, then publishes telemetry. If telemetry fails, the script reports the failure. For production, add retry logic around publish_telemetry().

Connectivity mismatch - data not appearing

If your device is configured for HTTP connectivity but your script uses MQTT (or vice versa), the data will still work - both protocols write to the same database. The connectivity setting is informational and affects which code snippets appear on the device detail page.

HTTP 429 - quota exhausted

You have hit the daily snapshot limit for your plan. Free plan allows 10 per day. Upgrade to Starter (50/day) or Business (200/day) if you need more.

HTTP 413 - image too large

The image exceeds the 500 KB limit. Reduce the JPEG quality or image dimensions:

img.save(buf, "JPEG", quality=60)      # lower quality
img.thumbnail((320, 240))               # smaller dimensions

HTTP 401 - invalid token

Double-check your DEVICE_ID and ACCESS_TOKEN. The token is only shown once at device creation. If you lost it, regenerate it from the device settings page.

MQTT vs HTTP - which to use?

	MQTT	HTTP
Best for	Continuous streaming, bidirectional control	Periodic uploads, camera snapshots
Connection	Persistent (keeps socket open)	Per-request (connect, send, disconnect)
Device config	Set connectivity to WiFi/Ethernet/4G + MQTT	Set connectivity to WiFi/4G + HTTP

Best Practices

• Use JPEG for photos - 5-10x smaller than PNG at equivalent visual quality
• Resize before uploading - 640x480 at 80% quality is typically under 100 KB
• Match data interval to cron - if your device is set to “Every 5 minutes”, run the script every 5 minutes
• Log failures - redirect output to a log file when running via cron
• Use motion detection - in production, trigger snapshots on events (motion, threshold breach) rather than fixed intervals to conserve your daily quota

Next Steps

• Camera Snapshots Reference - Full API reference and plan limits
• ESP32-CAM Snapshots - Upload snapshots from an ESP32-CAM (Arduino/C++)
• HTTP Data Ingestion - Full HTTP API reference
• Dashboard Alerts - Set up threshold alerts on your sensor data