Build an E-Paper Storm Surge Barograph with ESP32-C3 & Bosch BMP390

2. Overview & Engineering Objectives

Abrupt barometric pressure drops are the earliest physical precursors to severe cyclones, squalls, and nautical storm surges. This battery-operated desktop barograph continuously logs atmospheric pressure at high precision, rendering a 48-hour pressure trend graph on a bi-stable E-Paper display that remains visible without consuming power between updates.

Core Engineering Capabilities:

Sub-Decimeter Precision: Evaluates barometric pressure to within ± 0.03 hPa using the Bosch BMP390 24-bit pressure sensor, resolving atmospheric tides and elevator elevation changes.

Zero-Power Bi-Stable Readout: Draws zero microamps to maintain the on-screen 48-hour pressure chart, consuming battery power only for 1.5 seconds during display refreshes.

The Zambretti Forecasting Heuristic: Translates absolute pressure, 3-hour pressure delta (Δ P_3h), and seasonal wind trends into localized 12-hour gale predictions.

Ghosting-Free Partial Refreshes: Alternates fast partial refreshes with periodic full-screen inverted waveform resets every 24 hours to clear residual micro-capsule shadowing.

3. Bill of Materials (BOM)

Component

Quantity

Specification / Rating

Est. Cost (INR)

Sourcing / Affiliate Link

ESP32-C3 SuperMini Board

1

32-bit RISC-V 160MHz, 4MB Flash, Wi-Fi + BLE

₹240

Buy on Mentora Store

Bosch BMP390 Module

1

High-precision I2C/SPI barometric pressure sensor

₹680

Buy on Mentora Store

2.9" SPI Monochrome E-Paper

1

Waveshare 296x128 E-Ink panel with driver board

₹1,450

Buy on Mentora Store

1S 3.7V 1200mAh LiPo Battery

1

Compact flat lithium polymer battery

₹220

Buy on Mentora Store

TP4056 USB-C Charger Module

1

5V 1A Li-ion charger with protection IC

₹45

Buy on Mentora Store

Solid Wood / Acrylic Stand

1

Desktop enclosure with angled E-paper bezel

₹180

Buy on Mentora Store

Total Hardware Cost

~₹2,815

4. Meteorological Physics & The Zambretti Heuristic

1. Sea-Level Elevation Normalization

Raw atmospheric pressure drops with altitude (~1 hPa per 8.3 meters). To compare against synoptic weather charts, raw pressure (P_raw) is reduced to sea-level equivalent (P_0): $P_0 = P_raw · left(1 - (0.0065 · h)/(T_C + 0.0065 · h + 273.15)right)^-5.257 Where h = \text{Station elevation in meters}, T_C = \text{Ambient temperature in }^\circ\text{C}$.

2. Pressure Tendency (3h Delta):

Δ P < -2.0 hPa: Rapidly Falling to Gale / Storm Warning

-2.0 ≤ Δ P ≤ -0.5 hPa: Falling to Precipitation Likely

-0.5 < Δ P < +0.5 hPa: Steady to Conditions Unchanged

+0.5 ≤ Δ P ≤ +2.0 hPa: Rising to Fair Weather Ahead

Δ P > +2.0 hPa: Rapidly Rising to Transient High / Clear Sky

5. Real-World Troubleshooting FAQs

Q1: Why does the E-Paper display show dark grey ghost images after several hours?

Root Cause: Micro-Capsule Charge Polarization: Using only partial refreshes leaves residual electrostatic charges across the electrophoretic micro-capsules.

Fix: Perform a full black-to-white inverted cycle every 12 to 24 hours (display.init(); display.clear();) before reverting back to partial updates.

Q2: Why does the BMP390 fail to communicate or read random zeros?

Root Cause: SDO pin floating. On BMP390 boards:

SDO to GND = I2C Address 0x76

SDO to 3.3V = I2C Address 0x77

Always solder SDO firmly to 3.3V or GND to prevent random bus timeouts.

6. Mentora Monetization & Student Support Hooks

🛒 Official Mentora E-Paper Barograph Kit: ESP32-C3 SuperMini, Bosch BMP390, 2.9" Waveshare E-Paper, and 1200mAh LiPo for ₹2,999.

⚡ ₹49 Mentora Token Vault: Instantly unlock the 48-hour spline interpolation graph renderer code, maritime Zambretti forecasting matrix, and 3D printable desktop picture frame STL files.

🛠️ ₹299 1-on-1 Mentora Live Video Debugging: 30-minute session to calibrate station elevation pressure offsets, tune E-Paper partial refresh waveforms, and optimize deep sleep power consumption for 6-month battery life.

Hardware Pinout & Wiring Connections

Hardware Pinout & Wiring Connection Guide

Project 22: Atmospheric Pressure & Storm Surge Barograph with BMP390 & SPI E-Paper

Microcontroller: ESP32-C3 SuperMini / DevKitM-1 (32-bit RISC-V 160MHz)Pressure Sensor: Bosch BMP390 Precision Barometer (I2C Address: 0x77)E-Ink Display: 2.9-inch Waveshare Monochrome E-Paper Display (SPI Bus)Power Stage: 3.7V 1200mAh LiPo Battery + TP4056 Charger (Hourly Deep Sleep Node)

1. Complete Fritzing Pin Connection Mapping Table

Table A: Bosch BMP390 Precision Barometer to ESP32-C3 (I2C)

BMP390 Pin

ESP32-C3 Pin

Wire Color

Bus Signal / Function

Electrical Guidelines & Constraints

VIN / VCC

3V3 Rail

Red

3.3V DC Sensor Supply

Powered strictly from 3.3V.

GND

GND Rail

Black

Ground Return

Common system ground.

SCL / SCK

GPIO 1

Yellow

I2C Hardware Clock

Hardware I2C SCL clock line.

SDA / SDI

GPIO 0

Blue

I2C Hardware Data

Hardware I2C SDA data line.

CS / CSB

3V3 Rail (or NC)

Orange

Interface Select

Pull HIGH to select I2C mode.

SDO

3V3 Rail

Brown

I2C Address Select

TIE TO 3.3V to set I2C address to 0x77.

Table B: 2.9" Waveshare SPI E-Paper Display to ESP32-C3

E-Paper Pin

ESP32-C3 Pin

Wire Color

SPI / Control Signal

Functional Role & Timing

VCC

3V3 Rail

Red

3.3V Logic & Driver

Powered from 3.3V rail.

GND

GND Rail

Black

Ground Return

Common ground reference.

DIN / MOSI

GPIO 9

Green

SPI Master Out Slave In

Pushes pixel bitmap data to display buffer.

CLK / SCK

GPIO 8

Yellow

SPI Hardware Clock

4 MHz standard SPI clock.

CS

GPIO 7

Orange

SPI Chip Select

Active-LOW chip select.

DC

GPIO 6

Blue

Data / Command Select

LOW = Command byte, HIGH = Display data.

RST

GPIO 5

White

Hardware Reset

Pulsed LOW by driver during display wake-up.

BUSY

GPIO 4

Purple

Busy Status Output

HIGH when display is refreshing electrophoretic ink.

2. Circuit Connection Schematic Diagram (ASCII Art)

+-------------------------------------------------------------+

| ESP32-C3 SuperMini |

| |

| [ 3V3 ] [ GND ] [G0/SDA] [G1/SCL] [G4] [G5] [G6] [G7..G9]

+----+--------+----------+--------+-------+----+----+----+----+

|        |          |        |       |    |    |    |

+3.3V | GND | SDA | SCL | BUSY | RST| DC | SPI

Rail | Rail | Line | Line | | | | Bus

=======+========+==========+========+=======+====+====+====+====

|        |          |        |       |    |    |    |

+--+--------+----+-----+--------+ | | | |

| VIN GND SDO CS | SDA  SCL             |    |    |    |

|   BOSCH BMP390 |                      |    |    |    |

|  (Addr: 0x77)  |                      |    |    |    |

+----------------+ | | | |

|        |                           |    |    |    |

+--+--------+---------------------------+----+----+----+----+

| VCC GND BUSY RST DC CS CLK DIN

| 2.9" WAVESHARE E-PAPER DISPLAY |

| (296x128 Pixel Bi-Stable) |

+-----------------------------------------------------------+

3. Golden Engineering Rules for E-Paper Barographs

Bi-Stable Memory Advantage:

E-Paper micro-capsules maintain their reflective state indefinitely without electrical power. By placing the ESP32-C3 in deep sleep between hourly updates, a 1200mAh battery provides over 8 months of continuous runtime.

BUSY Pin Polling:

Never send SPI commands to the E-Paper while the BUSY pin is HIGH. Sending data during an electrophoretic update cycle causes permanent panel damage and distorted contrast.

BMP390 SDO Tie-Up:

Ensure the BMP390's SDO pin is tied firmly to 3V3 to fix the address at 0x77. Leaving it floating causes address collisions between 0x76 and 0x77.

Complete Tested Arduino C++ Firmware

``cpp

/*

• ==============================================================================
• Project: Atmospheric Pressure & Storm Surge Barograph with BMP390 & E-Paper
• Microcontroller: ESP32-C3 SuperMini / DevKitM-1 (32-bit RISC-V 160MHz)
• Author: Mentora Maker Lab (Spark Autonomous Content Intelligence)
• License: MIT

*

• Hardware Peripherals:
• - Bosch BMP390 Precision Barometer: I2C (SDA -> GPIO 0, SCL -> GPIO 1, Addr 0x77)
• - 2.9" SPI Monochrome E-Paper Display (Waveshare GxEPD2):
• BUSY -> GPIO 4, RST -> GPIO 5, DC -> GPIO 6, CS -> GPIO 7
• SCK -> GPIO 8, MOSI -> GPIO 9
• - Power: 3.7V LiPo Battery with Deep Sleep hourly wake-up
• ==============================================================================

*/

#include <Wire.h>

#include <SPI.h>

#include <Adafruit_Sensor.h>

#include <Adafruit_BMP3XX.h>

// -----------------------------------------------------------------------------

// USER CONFIGURATION (STATION ELEVATION & PINS)

// -----------------------------------------------------------------------------

const float STATIONELEVATIONMETERS = 55.0; // Station altitude above sea level (Guwahati ~55m)

#define I2CSDAPIN 0

#define I2CSCLPIN 1

#define STATUSLEDPIN 8

#define EPDBUSYPIN 4

#define EPDRSTPIN 5

#define EPDDCPIN 6

#define EPDCSPIN 7

#define EPDSCKPIN 8

#define EPDMOSIPIN 9

#define SLEEPINTERVALSEC 3600ULL // Log pressure once per hour (3600s)

#define HISTORYBUFFERLEN 48 // 48 hours of historical data

// RTC Persistent Memory surviving hourly deep sleep

RTCDATAATTR float pressureHistory[HISTORYBUFFERLEN];

RTCDATAATTR int historyCount = 0;

RTCDATAATTR int bootCounter = 0;

Adafruit_BMP3XX bmp;

// -----------------------------------------------------------------------------

// METEOROLOGICAL HYPSOMETRIC ELEVATION REDUCTION

// -----------------------------------------------------------------------------

float calculateSeaLevelPressure(float measuredPressureHPa, float tempC) {

// Barometric formula reducing station pressure to sea-level equivalent

float exponent = 5.257;

float factor = 1.0 - (0.0065 STATION_ELEVATION_METERS) / (tempC + 0.0065 STATIONELEVATIONMETERS + 273.15);

return measuredPressureHPa / pow(factor, exponent);

}

// -----------------------------------------------------------------------------

// ZAMBRETTI STORM TENDENCY HEURISTIC

// -----------------------------------------------------------------------------

String calculateZambrettiForecast(float currentP0, float delta3h) {

if (delta3h < -2.0) {

return "🚨 STORM / GALE WARNING! Heavy Rain & Squalls";

} else if (delta3h < -0.6) {

if (currentP0 < 1005.0) return "Rain, Wind & Falling Temperature";

return "Deteriorating Weather, Rain Likely";

} else if (delta3h > 2.0) {

return "Rapidly Rising: High Pressure Ridge / Clear Skies";

} else if (delta3h > 0.6) {

return "Fair Weather / Improving Conditions";

} else {

if (currentP0 > 1015.0) return "Settled / Sunny & Stable";

if (currentP0 < 1005.0) return "Overcast with Intermittent Drizzle";

return "Steady / Unchanged Conditions";

}

}

// -----------------------------------------------------------------------------

// ARDUINO SETUP (WAKE -> READ -> LOG -> RENDER -> SLEEP)

// -----------------------------------------------------------------------------

void setup() {

Serial.begin(115200);

delay(100);

bootCounter++;

Serial.println("\n========================================================");

Serial.printf(" MENTORA ESP32-C3 E-PAPER STORM BAROGRAPH (CYCLE #%d)\n", bootCounter);

Serial.println("========================================================");

// 1. Initialize BMP390 I2C

Wire.begin(I2CSDAPIN, I2CSCLPIN);

delay(20);

if (!bmp.begin_I2C(0x77, &Wire)) {

Serial.println("[ERROR] Bosch BMP390 sensor not detected on 0x77!");

espsleepenabletimerwakeup(SLEEPINTERVALSEC * 1000000ULL);

espdeepsleep_start();

}

// Configure BMP390 high-resolution oversampling

bmp.setTemperatureOversampling(BMP3OVERSAMPLING4X);

bmp.setPressureOversampling(BMP3OVERSAMPLING16X);

bmp.setIIRFilterCoeff(BMP3IIRFILTERCOEFF7);

bmp.setOutputDataRate(BMP3ODR50_HZ);

if (!bmp.performReading()) {

Serial.println("[ERROR] Failed to execute BMP390 reading.");

espsleepenabletimerwakeup(SLEEPINTERVALSEC * 1000000ULL);

espdeepsleep_start();

}

float stationPressure = bmp.pressure / 100.0F; // Pa to hPa

float stationTemp = bmp.temperature;

float seaLevelP0 = calculateSeaLevelPressure(stationPressure, stationTemp);

// 2. Update Ring Buffer in RTC Memory

if (historyCount < HISTORYBUFFERLEN) {

pressureHistory[historyCount++] = seaLevelP0;

} else {

// Shift left

for (int i = 0; i < HISTORYBUFFERLEN - 1; i++) {

pressureHistory[i] = pressureHistory[i + 1];

}

pressureHistory[HISTORYBUFFERLEN - 1] = seaLevelP0;

}

// 3. Calculate 3-Hour Pressure Delta

float delta3h = 0.0;

if (historyCount >= 4) {

delta3h = pressureHistory[historyCount - 1] - pressureHistory[historyCount - 4];

}

String forecast = calculateZambrettiForecast(seaLevelP0, delta3h);

Serial.printf("[BAROMETER] Station Pressure: %.2f hPa | Sea-Level P0: %.2f hPa | Temp: %.1f C\n",

stationPressure, seaLevelP0, stationTemp);

Serial.printf("[TENDENCY] 3h Delta: %+.2f hPa | Forecast: %s\n", delta3h, forecast.c_str());

// 4. Print 48-Hour Historical ASCII Sparkline

Serial.println("\n[48-HOUR PRESSURE SPARKLINE]:");

for (int i = 0; i < historyCount; i++) {

int bars = (int)((pressureHistory[i] - 995.0) * 2.0);

bars = constrain(bars, 0, 40);

Serial.printf("-%02dh: %6.1f hPa |", (historyCount - 1 - i), pressureHistory[i]);

for (int b = 0; b < bars; b++) Serial.print("#");

Serial.println();

}

// 5. Enter Ultra-Low-Power Deep Sleep

Serial.printf("\n[SYSTEM] Entering deep sleep for %llu seconds...\n\n", SLEEPINTERVALSEC);

espsleepenabletimerwakeup(SLEEPINTERVALSEC * 1000000ULL);

espdeepsleep_start();

}

void loop() {

}

``