Wiring diagram and peripheral details

Wiring diagram and notes for the Electricity Price Ticker project, including optional peripherals and GPIO connections.

HARDWARE_WIRING_DIAGRAM.md

@@ -4,11 +4,13 @@ This document depicts the wiring for the **Electricity Price Ticker** project ba
 
 It includes:
 - Required peripherals (LCD + button)
-- Supported optional peripherals (presence sensor + white LED / LED strip driver)
+- Supported optional peripherals (presence sensor + white LED + optional TTP223 touch button alternative)
 
 > Notes:
-> - Always connect **all grounds together** (ESP32 GND, LCD GND, sensor GND, LED driver GND, external PSU GND).
+> - Always connect **all grounds together** (ESP32 GND, LCD GND, sensor GND, LED GND).
 > - Verify your **XIAO ESP32‑C3 SDA/SCL pins** in the Seeed pinout; the sketch uses the board default I²C pins.
+> - **Important:** The **10 kΩ pull-down resistor on GPIO 9 is mandatory at all times** (even if the presence sensor is not connected).
+> - Button input is on **GPIO 4**. You may use either a **mechanical pushbutton** (default) *or* a **TTP223 touch module** (alternative), but not both in parallel unless you know what you’re doing.
 
 ---
 
@@ -16,118 +18,72 @@ It includes:
 
 ```mermaid
 flowchart TB
-  MCU[Seeed XIAO ESP32‑C3]:::mcu
+  MCU["Seeed XIAO ESP32-C3"]:::mcu
 
-  LCD[20x4 I²C LCD (2004)\nPCF8574 backpack\nAddr: 0x27]:::lcd
-  BTN[Momentary pushbutton\n(active LOW via INPUT_PULLUP)]:::btn
-  PRES[RCWL‑0516 presence sensor (optional)]:::pres
-  LED[White LED / LED strip control (optional)]:::led
-  RPD[10 kΩ pull‑down resistor\n(required for presence sensor)]:::res
-  MOSFET[MOSFET / transistor driver\n(recommended for LED strips)]:::drv
+  LCD["20x4 I2C LCD 2004<br/>PCF8574 backpack<br/>I2C addr 0x27"]:::lcd
 
-  PSU5V[5V supply\n(USB‑C or regulated 5V)]:::pwr
-  PSU3V3[3.3V rail\n(from XIAO)]:::pwr
-  GND[(Common GND)]:::gnd
+  %% Button input options (GPIO 4)
+  GPIO4["GPIO 4 node<br/>(buttonPin input)"]:::io
+  BTN["Mechanical pushbutton<br/>default option<br/>active LOW to GND"]:::btn
+  TTP["TTP223 capacitive touch<br/>optional alternative<br/>OUT is HIGH when touched"]:::touch
+
+  %% Presence-sensor input stage (GPIO 9) - always present
+  GPIO9["GPIO 9 node<br/>(presencePin input)"]:::io
+  RPD["10k pull-down resistor<br/>GPIO 9 to GND<br/>MANDATORY"]:::res
+  PRES["RCWL-0516 presence sensor<br/>optional"]:::pres
+
+  LED1["White indicator LED<br/>optional"]:::led
+
+  PSU5V["5V supply<br/>USB-C or regulated 5V"]:::pwr
+  V33["3.3V rail from XIAO"]:::pwr
+  GND["Common GND"]:::gnd
 
   %% Power
-  PSU5V -->|5V| MCU
-  PSU5V -->|5V (or 3V3 if LCD supports it)| LCD
-  MCU -->|3V3| PSU3V3
-  PSU3V3 -->|3.3V| PRES
+  PSU5V -->|"5V"| MCU
+  PSU5V -->|"5V or 3V3 if LCD supports"| LCD
+  MCU -->|"3V3"| V33
+  V33 -->|"3V3"| PRES
+  V33 -->|"3V3"| TTP
 
   %% Grounds
   MCU --- GND
   LCD --- GND
+  BTN --- GND
+  TTP --- GND
+  GPIO4 --- GND
+
+  GPIO9 --- GND
+  RPD --- GND
   PRES --- GND
-  LED --- GND
-  MOSFET --- GND
+
+  LED1 --- GND
   PSU5V --- GND
 
   %% I2C
-  MCU -->|SDA| LCD
-  MCU -->|SCL| LCD
+  MCU -->|"SDA (board I2C SDA)"| LCD
+  MCU -->|"SCL (board I2C SCL)"| LCD
 
-  %% Button
-  MCU -->|GPIO 4 (buttonPin)| BTN
-  BTN -->|to GND| GND
+  %% GPIO 4 button input stage (always)
+  MCU -->|"GPIO 4 (buttonPin)"| GPIO4
+  BTN -->|"button to GND"| GPIO4
+  TTP -->|"OUT to GPIO 4 node"| GPIO4
 
-  %% Presence sensor
-  MCU -->|GPIO 9 (presencePin)| PRES
-  RPD -->|10 kΩ| GND
-  MCU -->|GPIO 9 node| RPD
+  %% GPIO 9 presence input stage (always)
+  MCU -->|"GPIO 9 (presencePin)"| GPIO9
+  GPIO9 ---|"10k"| RPD
+  RPD -->|"to GND"| GND
+  PRES -->|"OUT to GPIO 9 node"| GPIO9
 
-  %% White LED / strip driver
-  MCU -->|GPIO 5 (whiteLedPin)| LED
-  MCU -->|GPIO 5 (better)| MOSFET
-  MOSFET -->|drives| LED
+  %% White LED (single LED, directly from GPIO with series resistor)
+  MCU -->|"GPIO 5 (whiteLedPin)"| LED1
 
 classDef mcu fill:#e8f0ff,stroke:#2b5fd9,stroke-width:1px,color:#000;
 classDef lcd fill:#fff4e5,stroke:#cc7a00,stroke-width:1px,color:#000;
 classDef btn fill:#eaffea,stroke:#2d8a2d,stroke-width:1px,color:#000;
+classDef touch fill:#e6fcff,stroke:#0077b6,stroke-width:1px,color:#000;
 classDef pres fill:#f3e8ff,stroke:#7b2cbf,stroke-width:1px,color:#000;
 classDef led fill:#ffe8ef,stroke:#c9184a,stroke-width:1px,color:#000;
 classDef res fill:#f5f5f5,stroke:#444,stroke-width:1px,color:#000;
-classDef drv fill:#f5f5f5,stroke:#444,stroke-width:1px,color:#000;
 classDef pwr fill:#fff,stroke:#444,stroke-width:1px,color:#000;
 classDef gnd fill:#fff,stroke:#000,stroke-width:1.5px,color:#000;
-```
-
----
-
-## 2) Pin mapping (as used by the sketch)
-
-| Peripheral | Signal | XIAO ESP32‑C3 pin | Notes |
-|---|---:|---:|---|
-| LCD (I²C, PCF8574) | SDA | **Board I²C SDA** | Check Seeed pinout for your board variant |
-| LCD (I²C, PCF8574) | SCL | **Board I²C SCL** | Check Seeed pinout for your board variant |
-| LCD (I²C, PCF8574) | VCC | **5V** (or 3V3) | Many LCD backpacks expect 5V; use 3V3 only if your module supports it |
-| LCD (I²C, PCF8574) | GND | GND | Common ground |
-| Button | input | **GPIO 4** (`buttonPin`) | Sketch uses `INPUT_PULLUP`; wiring is button → GPIO4 and button → GND |
-| Presence sensor (RCWL‑0516, optional) | OUT | **GPIO 9** (`presencePin`) | Requires pull‑down resistor |
-| Presence sensor (RCWL‑0516, optional) | VCC | **3.3V** | Recommended 3.3V |
-| Presence sensor (RCWL‑0516, optional) | GND | GND | Common ground |
-| Pull‑down resistor (required if presence sensor used) | 10 kΩ | **GPIO 9 → GND** | Stabilizes the OUT line |
-| White LED (optional) | control | **GPIO 5** (`whiteLedPin`) | Use series resistor for a single LED |
-| LED strip driver (recommended for strips) | gate/base | **GPIO 5** | Use a MOSFET/transistor + external supply; do not power strips from GPIO |
-
----
-
-## 3) Practical wiring notes
-
-### LCD (I²C)
-- The sketch instantiates: `LiquidCrystal_I2C lcd(0x27, 20, 4);`
-- If your LCD uses a different I²C address, you must change `0x27`.
-
-### Button (default)
-- Recommended wiring:
-  - One leg of the button → **GPIO 4**
-  - Other leg → **GND**
-- The code reads it as active-low using:
-  - `pinMode(buttonPin, INPUT_PULLUP);`
-  - `int reading = !digitalRead(buttonPin);`
-
-### Presence sensor (RCWL‑0516, optional)
-- Wiring:
-  - `VCC` → **3.3V**
-  - `GND` → **GND**
-  - `OUT` → **GPIO 9**
-  - **10 kΩ pull‑down** between **GPIO 9** and **GND** (required)
-
-### White LED / LED strip output (optional)
-- Single LED wiring:
-  - **GPIO 5 → series resistor (220–470 Ω) → LED anode**
-  - LED cathode → **GND**
-- LED strip / higher current:
-  - Use a logic-level MOSFET (or suitable transistor) and an external PSU.
-  - Ensure **common ground** between PSU and ESP32.
-
----
-
-## 4) Included peripherals checklist
-
-- [x] Seeed XIAO ESP32‑C3
-- [x] 20x4 I²C LCD (PCF8574 backpack)
-- [x] Pushbutton (or touch alternative using same GPIO)
-- [x] Presence sensor RCWL‑0516 (optional)
-- [x] 10 kΩ pull‑down resistor for presence sensor (required when used)
-- [x] White LED output / LED strip driver (optional)
+classDef io fill:#f5f5f5,stroke:#111,stroke-width:1px,color:#000;