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Hardware Setup Guide

Hardware: 2.8" ESP32-32E Display Module

This firmware is configured for the 2.8-inch ESP32-32E Display Module which integrates:

  • ESP32-WROOM-32E microcontroller
  • 2.8" TFT LCD (240x320 resolution, ILI9341 driver)
  • Resistive touchscreen (XPT2046 controller)
  • Onboard peripherals (MicroSD, Audio, RGB LED, etc.)

Documentation Source: lcdwiki.com - 2.8inch ESP32-32E Display

Pin Configuration

LCD Display Pins (SPI Bus)

The LCD uses a dedicated SPI bus:

Pin Function GPIO Description
TFT_CS GPIO15 LCD screen selection control signal (low level effective)
TFT_DC GPIO2 LCD command/data selection (high=data, low=command)
TFT_RST GPIO4 LCD reset control signal (low level reset, shared with ESP32 EN pin)
TFT_SCLK GPIO14 LCD SPI bus clock signal
TFT_MOSI GPIO13 LCD SPI bus write data signal
TFT_MISO GPIO12 LCD SPI bus read data signal
TFT_BL GPIO21 LCD backlight control (high=on, low=off)

Touch Screen Pins (Separate SPI Bus)

Important: The touch screen uses its own dedicated SPI bus, separate from the LCD SPI bus.

Pin Function GPIO Description
TOUCH_CS GPIO33 Touch chip selection control signal (low level effective)
TOUCH_IRQ GPIO36 Touch interrupt signal (low level = touch event)
TOUCH_SCLK GPIO25 Touch SPI bus clock signal
TOUCH_MOSI GPIO32 Touch SPI bus write data signal
TOUCH_MISO GPIO39 Touch SPI bus read data signal (input only)

Flow Meter (YF-S201)

Pin Function GPIO Description
FLOW_METER_PIN GPIO26 Flow meter interrupt signal (Hall effect sensor output)

Note: Changed from GPIO25 to GPIO26 to avoid conflict with TOUCH_SCLK. GPIO26 is interrupt-capable and was previously used for Audio DAC (can be repurposed).

Available Peripherals

MicroSD Card

Pin Function GPIO Description
SD_CS GPIO5 SD card select signal (low level effective)
SD_MOSI GPIO23 SD card SPI bus write data (shared with LCD SPI)
SD_SCLK GPIO18 SD card SPI bus clock (shared with LCD SPI)
SD_MISO GPIO19 SD card SPI bus read data (shared with LCD SPI)

Note: MicroSD shares SPI pins with LCD. Cannot be used simultaneously without careful management.

Audio

Pin Function GPIO Description
AUDIO_EN GPIO4 Audio enable signal (low level enable, high level disable)
AUDIO_DAC GPIO26 Audio signal DAC output signal

Note: GPIO4 conflicts with TFT_RST, so audio enable cannot be used simultaneously.

RGB LED

Pin Function GPIO Description
LED_R GPIO22 Red LED control (common anode: low=on, high=off)
LED_G GPIO16 Green LED control (common anode: low=on, high=off)
LED_B GPIO17 Blue LED control (common anode: low=on, high=off)

Buttons

Pin Function GPIO Description
BOOT GPIO0 Download mode select button (press and hold to power on, then release to enter download mode)
EN EN ESP32 reset button (low level reset, shared with LCD reset)

Serial Port

Pin Function GPIO Description
RXD0 GPIO3 Serial port receiving signal (can be used as GPIO if serial not used)
TXD0 GPIO1 Serial port transmit signal (can be used as GPIO if serial not used)

Battery Monitoring

Pin Function GPIO Description
BAT_ADC GPIO34 Battery voltage ADC input (input only, ADC1_CH6)

SPI Peripheral

Pin Function GPIO Description
SPI_CS GPIO27 SPI peripheral chip selection (low level effective, can be GPIO if not used)
SPI_SCLK GPIO18 SPI bus clock (shared with MicroSD/LCD, currently used for LCD)
SPI_MISO GPIO19 SPI bus read data (shared with MicroSD/LCD, currently used for LCD)
SPI_MOSI GPIO23 SPI bus write data (shared with MicroSD/LCD, currently used for LCD)

Not Connected (Input Only)

Pin Function GPIO Description
NC GPIO35 Not connected, can only be used as input IO (ADC1_CH7)

Pin Conflicts and Notes

Current Pin Usage

  • GPIO4: TFT_RST (conflicts with AUDIO_EN)
  • GPIO18, GPIO19, GPIO23: LCD SPI (shared with MicroSD/SPI peripheral)
  • GPIO25: TOUCH_SCLK (touch SPI clock)
  • GPIO26: FLOW_METER_PIN (flow meter interrupt, was Audio DAC)
  • GPIO34, GPIO35, GPIO36, GPIO39: Input-only pins (ADC or touch)

Available for Future Use

  • GPIO27: SPI peripheral CS (can be GPIO if not used)
  • GPIO32: Touch MOSI (currently used, but could be repurposed if touch not needed)

Flow Meter Setup (YF-S201)

Wiring

  • Red wire → 5V (ESP32 5V pin)
  • Black wire → GND (ESP32 GND)
  • Yellow wire → GPIO 26 (signal output, interrupt-capable pin)

Note: Changed from GPIO25 to GPIO26 to avoid conflict with TOUCH_SCLK. GPIO26 is interrupt-capable and available for use.

Specifications

  • Flow rate range: 1-30 liters per minute
  • Accuracy: ±10%
  • Pulses per liter: 450
  • Operating voltage: 4.5V to 18V DC
  • Maximum current: 15mA at 5V

How It Works

The YF-S201 uses a Hall effect sensor to detect a spinning rotor. Each rotation generates a pulse. The flow rate is calculated from the pulse frequency:

  • Flow Rate (L/min) = Pulse Frequency (Hz) / 7.5

The firmware automatically:

  • Counts pulses via hardware interrupt
  • Calculates flow rate every second
  • Tracks total volume
  • Provides API functions to read values

Configuration Files

include/config.h

Contains all pin definitions and hardware configuration:

  • Display pins
  • Touch pins
  • Flow meter pin
  • WiFi/MQTT settings
  • Operating mode (Test/Production)

lib/TFT_eSPI_Config/User_Setup.h

TFT_eSPI library configuration:

  • Display driver (ILI9341)
  • Pin assignments
  • SPI frequency settings
  • Display resolution

Testing Your Setup

  1. Upload firmware with correct pin configuration
  2. Check serial output for initialization messages: 
    pio device monitor
  3. Verify display:
    • Splashscreen should appear
    • Backlight should turn on
    • Main screen should display (logo, QR code, etc.)
  4. Test touch:
    • Touch screen should respond
    • Check serial output for touch coordinates
  5. Test flow meter:
    • Connect flow meter
    • Check serial output for flow readings
    • Verify flow rate calculations

Troubleshooting

Display Issues

  • Display shows nothing:

    • Check backlight pin (GPIO21) - verify it's turning on
    • Verify SPI connections (GPIO13, GPIO12, GPIO14)
    • Check TFT_CS pin (GPIO15)
    • Verify power supply is adequate

  • Display shows garbage/corrupted image:

    • Check SPI speed settings
    • Verify all SPI connections are correct
    • Check display driver selection (ILI9341)

  • Backlight not working:

    • Verify GPIO21 is configured correctly
    • Check TFT_BL pin connection
    • Verify backlight control logic (HIGH = on)

Touch Issues

  • Touch not working:

    • Verify touch uses separate SPI bus (GPIO25, GPIO32, GPIO39)
    • Check TOUCH_CS pin (GPIO33)
    • Verify TOUCH_IRQ pin (GPIO36)
    • Check serial output for touch initialization messages
    • Touch may need calibration

  • Touch coordinates incorrect:

    • Check touch calibration values in code
    • Verify touch SPI communication is working
    • Check serial output for raw touch values

Flow Meter Issues

  • Flow meter shows no reading:

    • Check wiring (Red→5V, Black→GND, Yellow→GPIO26)
    • Verify GPIO26 is interrupt-capable
    • Ensure liquid is actually flowing
    • Check serial output for pulse count

  • Flow readings inaccurate:

    • Check for air bubbles in flow path
    • Verify sensor is properly installed
    • Check calibration factor (7.5 pulses per L/min)

Pin Conflict Issues

  • GPIO4 conflict: Used for TFT_RST, conflicts with AUDIO_EN
    • Solution: Cannot use audio enable if display reset is needed
  • SPI sharing: LCD, MicroSD, and SPI peripheral share GPIO18, GPIO19, GPIO23
    • Solution: Cannot use all simultaneously without careful management
  • GPIO26: Now used for FLOW_METER_PIN (was Audio DAC, can be repurposed)

References