Serial Data Logger and Charts

Use the whole kit as a data logger: one CSV row of soil, water, temperature, humidity and pressure every few seconds. Paste it into a spreadsheet and chart what happens to a plant pot over an afternoon of watering and drying.

One of 7 projects in the ESP32 Plant Monitoring Learning Kit — the parts below are from that kit.

What you build and learn

• Logging sensor data as CSV
• Importing Serial Monitor output into a spreadsheet
• Making line charts from time-series data
• Calibrating after the fact, in the spreadsheet

What this project uses

Every item is in the kit — nothing extra to buy.

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Completed main build

In the kit

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computer

In the kit

USB data cable ESP32 38-Pin USB Type-C WiFi and Bluetooth Development Board - Dual-Core 240MHz DIY-342

In the kit

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spreadsheet software

In the kit

Basics Jumper Wire Assorted Pack 120 Pieces - Male-to-Male, Male-to-Female, Female-to-Female 10cm Ribbon Cables for… DIY-212

In the kit

Basics Transparent 830 Points Solderless Breadboard Clear Prototype Circuit Board MB-102 High Quality DIY Electronic… DIY-295

In the kit

Build this with

ESP32 Plant Monitoring Learning Kit

All 6 parts in one box, with this project and 6 more to build from them.

AED 65.00 See the kit Add kit to cart

Need only these parts? Order them loose · from AED 69.62 ▾

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USB data cable ESP32 38-Pin USB Type-C WiFi and Bluetooth Development Board - Dual-Core 240MHz DIY-342 · ×1

AED 28.85

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Basics Jumper Wire Assorted Pack 120 Pieces - Male-to-Male, Male-to-Female, Female-to-Female 10cm Ribbon Cables for… DIY-212 · ×1

AED 25.02

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Basics Transparent 830 Points Solderless Breadboard Clear Prototype Circuit Board MB-102 High Quality DIY Electronic… DIY-295 · ×1

AED 15.75

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Selected parts AED 69.62

Add 3 parts to cart

One of each part. Packs (resistor assortment, jumper wires) already hold more than a single build needs. Completed main build, computer, spreadsheet software: included in the kit, ask us for it loose. Delivery is AED 20, free on orders AED 100+.

Connections

Unplug USB before you change any wire. Pin names are the labels printed on the board.

Step by step

1. Build the main project wiring (or keep it from the main build): BME280 on GPIO21/22, soil on GPIO34, water on GPIO35.
2. For a quick test leave LOG_EVERY_S at 5. For a real afternoon, change it to 300 (one row every 5 minutes).
3. Upload the Serial data logger and charts sketch. Open Tools → Serial Monitor at 115200 baud, with the line ending set to Newline. Write down the clock time when it starts.
4. Push the soil probe into a pot of dry-ish soil and leave the computer running. Keep the water sensor out of water unless you are doing a short test.
5. After a few rows, water the plant and keep logging for an hour or more.
6. Untick 'Show timestamp' in the Serial Monitor, then copy all the text and paste it into a spreadsheet. Use Data → Split text to columns (comma) if it lands in one column.
7. Make a line chart of soil_raw against t_s, and another of temperature and humidity.

Sketch for this project

Written for the board in the kit. Copy it into the Arduino IDE; change the pin numbers if you wire it differently.

/*
  ESP32 Plant Monitoring Learning Kit
  Project 5: Serial data logger and charts

  Wiring: the whole kit - soil GPIO34, water GPIO35, BME280 on I2C 21/22.

  What you learn: a sensor reading on its own says little; a log over an
  afternoon tells the story. This sketch prints one CSV row every
  LOG_EVERY_S seconds. Copy the Serial monitor into a spreadsheet, make a
  chart, and you have the watering history. Raw values are logged on
  purpose: calibrate later, in the spreadsheet, without re-running.
*/

#include <Wire.h>
#include <Adafruit_Sensor.h>
#include <Adafruit_BME280.h>

Adafruit_BME280 bme;

const int SOIL_PIN = 34;
const int WATER_PIN = 35;
const int LOG_EVERY_S = 5;        // 5 s here; 300 s for a real afternoon
const int ADC_SAMPLES = 16;

unsigned long rowNumber = 0;
unsigned long lastRow = 0;
bool bmeOk = false;

int readAverage(int pin) {
  long sum = 0;
  for (int i = 0; i < ADC_SAMPLES; i++) { sum += analogRead(pin); delay(2); }
  return sum / ADC_SAMPLES;
}

void setup() {
  Serial.begin(115200);
  pinMode(SOIL_PIN, INPUT);
  pinMode(WATER_PIN, INPUT);
  analogReadResolution(12);
  Wire.begin(21, 22);
  bmeOk = bme.begin(0x76, &Wire);
  Serial.println("row,t_s,soil_raw,water_raw,temp_c,humidity_pct,pressure_hpa");
}

void loop() {
  if (rowNumber > 0 && millis() - lastRow < (unsigned long)LOG_EVERY_S * 1000UL) return;
  lastRow = millis();
  rowNumber++;
  Serial.print(rowNumber); Serial.print(",");
  Serial.print(millis() / 1000); Serial.print(",");
  Serial.print(readAverage(SOIL_PIN)); Serial.print(",");
  Serial.print(readAverage(WATER_PIN)); Serial.print(",");
  if (bmeOk) {
    Serial.print(bme.readTemperature(), 1); Serial.print(",");
    Serial.print(bme.readHumidity(), 1); Serial.print(",");
    Serial.println(bme.readPressure() / 100.0, 1);
  } else {
    Serial.println("NA,NA,NA");
  }
}

• LOG_EVERY_S (5) sets the time between rows. 300 = every 5 minutes.
• ADC_SAMPLES (16) readings are averaged for each analog value.
• The BME280 columns show NA,NA,NA if the sensor is not found, so you can log soil only.

What you should see

• A header row,t_s,soil_raw,water_raw,temp_c,humidity_pct,pressure_hpa, then one row per interval.
• After watering, soil_raw changes sharply then slowly drifts back as the pot drains and dries.
• Temperature and humidity following the room through the day.

If it doesn't work

Try next

• Add a percent column in the spreadsheet using your calibration endpoints.
• Log two pots with different soils one after the other and compare drying speed.

More from this kit

All projects →