SIMUT — Wiring Guide

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Pinout Diagram — ILI9341 TFT + XPT2046 Touch

                    Raspberry Pi Pico W
                  ┌────────────────────────┐
                  │  ╭──────────────────╮  │
    SLOT  0 ──────┤0 │                  │  │
    SLOT  1 ──────┤1 │                  │  │
    SLOT  2 ──────┤2 │                  │  │
    SLOT  3 ──────┤3 │                  │  │
    SLOT  4 ──────┤4 │                  │  │
    SLOT  5 ──────┤5 │                  │  │
    SLOT  6 ──────┤6 │                  │  │
    SLOT  7 ──────┤7 │                  │  │
    SLOT  8 ──────┤8 │                  │  │
    SLOT  9 ──────┤9 │                  │  │
    SLOT 10 ──────┤10│     RP2040       │  │
    SLOT 11 ──────┤11│                  │  │
    SLOT 12 ──────┤12│                  │  │
    SLOT 13 ──────┤13│                  │  │
    SLOT 14 ──────┤14│                  │  │
    SLOT 15 ──────┤15│                  │  │
                  │  │    Dual-Core     │  │
     TFT MISO   ──┤16│    133 MHz       │  │── GND ──── Common Ground
     Touch CS   ──┤17│                  │  │── 3V3 ──── Display VCC
     TFT SCK    ──┤18│                  │  │── 3V3 ──── Sensors VCC
     TFT MOSI   ──┤19│                  │  │
     Touch IRQ  ──┤20│                  │  │
                  │  │                  │  │
     Buzzer     ──┤22│                  │  │
                  │  │                  │  │
     TFT RST    ──┤26│                  │  │
     TFT DC     ──┤27│                  │  │
     TFT CS     ──┤28│                  │  │
                  │  ╰──────────────────╯  │
                  │        ┌──────┐        │
                  │        │ micro│        │
                  │        │ USB  │        │
                  │        └──────┘        │
                  └────────────────────────┘

GPIO 0–15 are universal configurable slots. Each slot accepts any sensor type (DS18B20, DHT22, BME280). The user assigns sensor type and GPIOs via CLI before physical assembly. See Slot Configuration below.

Pinout Diagram — BME280 on I2C (Example)

                    Raspberry Pi Pico W
                  ┌────────────────────────┐
                  │  ╭──────────────────╮  │    BME280
    SLOT  0 ──────┤0 │                  │  │   ┌──────────┐
    SLOT  1 ──────┤1 │                  │  │   │ VCC → 3V3│
    SLOT  2 ──────┤2 │                  │  │   │ GND → GND│
    SLOT  3 ──────┤3 │                  │  │   │ SDA → GP4│
   ╭ BME280 SDA ──┤4 │     RP2040       │  │   │ SCL → GP5│
   │ BME280 SCL ──┤5 │                  │  │   │ CSB → 3V3│
   │  SLOT  6 ────┤6 │    Dual-Core     │  │   │ SDO → GND│
   │  SLOT  7 ────┤7 │    133 MHz       │  │── GND ────┤
   │  SLOT  8 ────┤8 │                  │  │── 3V3 ────┤
   │  SLOT  9 ────┤9 │                  │  │   └──────────┘
   │  SLOT 10 ────┤10│                  │  │
   │  SLOT 11 ────┤11│                  │  │   2× 4.7 kΩ pull-up
   │  SLOT 12 ────┤12│                  │  │   on SDA and SCL to 3V3
   │  SLOT 13 ────┤13│                  │  │   (usually built into module)
   │  SLOT 14 ────┤14│                  │  │
   ╰─ SLOT 15 ────┤15│                  │  │
                  │  │                  │  │
    TFT MISO   ───┤16│                  │  │
    ...            ...                  ...  ...
                  └────────────────────────┘

Pinout Diagram — HD44780 16×2 (I2C Mode)

                    Raspberry Pi Pico W
                  ┌────────────────────────┐
                  │  ╭──────────────────╮  │
    SLOT  0 ──────┤0 │                  │  │
    SLOT  1 ──────┤1 │                  │  │
    SLOT  2 ──────┤2 │                  │  │
    SLOT  3 ──────┤3 │                  │  │
    SLOT  4 ──────┤4 │                  │  │
    SLOT  5 ──────┤5 │                  │  │
    SLOT  6 ──────┤6 │                  │  │
    SLOT  7 ──────┤7 │                  │  │
    SLOT  8 ──────┤8 │                  │  │
    SLOT  9 ──────┤9 │                  │  │
    SLOT 10 ──────┤10│     RP2040       │  │
    SLOT 11 ──────┤11│                  │  │
    SLOT 12 ──────┤12│                  │  │
    SLOT 13 ──────┤13│                  │  │
    SLOT 14 ──────┤14│                  │  │
    SLOT 15 ──────┤15│                  │  │
                  │  │                  │  │
                  │  │    Dual-Core     │  │── GND ──── Common Ground
                  │  │    133 MHz       │  │── 5V  ──── LCD VCC (via backpack)
                  │  │                  │  │── 3V3 ──── Sensors VCC
     Buzzer     ──┤22│                  │  │
                  │  │                  │  │
     LCD SCL    ──┤27│                  │  │
     LCD SDA    ──┤26│                  │  │
                  │  ╰──────────────────╯  │
                  │        ┌──────┐        │
                  │        │ micro│        │
                  │        │ USB  │        │
                  │        └──────┘        │
                  └────────────────────────┘

Pinout Diagram — HD44780 16×2 (Parallel 4-bit Mode)

                    Raspberry Pi Pico W
                  ┌────────────────────────┐
                  │  ╭──────────────────╮  │
    SLOT  0 ──────┤0 │                  │  │
    SLOT  1 ──────┤1 │                  │  │
    SLOT  2 ──────┤2 │                  │  │
    SLOT  3 ──────┤3 │                  │  │
    SLOT  4 ──────┤4 │                  │  │
    SLOT  5 ──────┤5 │                  │  │
    SLOT  6 ──────┤6 │                  │  │
    SLOT  7 ──────┤7 │                  │  │
    SLOT  8 ──────┤8 │                  │  │
    SLOT  9 ──────┤9 │                  │  │
    SLOT 10 ──────┤10│     RP2040       │  │
    SLOT 11 ──────┤11│                  │  │
    SLOT 12 ──────┤12│                  │  │
    SLOT 13 ──────┤13│                  │  │
    SLOT 14 ──────┤14│                  │  │
    SLOT 15 ──────┤15│                  │  │
                  │  │                  │  │
     LCD RS     ──┤16│    Dual-Core     │  │
     LCD EN     ──┤17│    133 MHz       │  │── GND ──── Common Ground
     LCD D4     ──┤18│                  │  │── 5V  ──── LCD VCC
     LCD D5     ──┤19│                  │  │── 3V3 ──── Sensors VCC
     LCD D6     ──┤20│                  │  │
     LCD D7     ──┤21│                  │  │
     Buzzer     ──┤22│                  │  │
                  │  ╰──────────────────╯  │
                  │        ┌──────┐        │
                  │        │ micro│        │
                  │        │ USB  │        │
                  │        └──────┘        │
                  └────────────────────────┘

Slot Configuration

Slots are not pre-assigned to a specific sensor type. Use the CLI to configure each slot before wiring:

gpio                          # Show GPIO resource map
sensor <n> create <type>      # Create a slot (shows pin requirements)
sensor <n> pin <idx>,<gpio>   # Assign GPIO to a pin
sensor <n> name "<name>"      # Set friendly name
sensor <n> active on          # Activate (validates all pins assigned)
write memory                  # Persist to flash

Sensor type GPIO requirements

Type	GPIOs needed	Pin roles	Max on 16 GPIOs
DS18B20	1	1-Wire (pull-up)	16
DHT22	1	Data (pull-up)	16
BME280	2	SDA, SCL (pull-up)	8

Example: 10× DS18B20 + 2× BME280 = 10 + 4 = 14 GPIOs. 2 GPIOs remain free.

BME280 Wiring (I2C)

The BME280 module typically comes on a breakout board with 6 pins:

BME280 Pin	Connect to
VCC	3V3 (Pico W pin 36)
GND	GND (Pico W pin 38)
SDA	GPIO assigned to slot pin[0] (SDA role)
SCL	GPIO assigned to slot pin[1] (SCL role)
CSB	3V3 (I2C mode — chip select tied high)
SDO	GND (address 0x76) or 3V3 (address 0x77)

I2C pull-ups: Most BME280 modules include 4.7 kΩ pull-ups on SDA/SCL. If yours doesn’t, add external 4.7 kΩ resistors from SDA to 3V3 and SCL to 3V3.

Example CLI setup for BME280 on GPIO 4 (SDA) + GPIO 5 (SCL):

sensor 0 create bme280
sensor 0 pin 0,4    # SDA → GPIO 4
sensor 0 pin 1,5    # SCL → GPIO 5
sensor 0 name "Lab Pressure"
sensor 0 active on
write memory

Pin Reference — ILI9341 TFT + XPT2046 Touch (default)

GPIO	Function	Connection
0–15	SLOT 0–15 (configurable)	Any sensor type: DS18B20 (1-Wire), DHT22 (Data), or BME280 (I2C SDA/SCL)
16	SPI0 MISO	TFT MISO + Touch MISO (shared bus)
17	SPI0 CS0	XPT2046 Touch CS
18	SPI0 SCK	TFT SCK + Touch SCK (shared bus)
19	SPI0 MOSI	TFT MOSI + Touch MOSI (shared bus)
20	GPIO	XPT2046 Touch IRQ (PENIRQ)
22	PIO	Passive Buzzer (+)
26	GPIO	TFT RST (Reset)
27	GPIO	TFT DC (Data/Command)
28	GPIO	TFT CS (Chip Select)

Pin Reference — HD44780 16×2 I2C (SIMUT_DISPLAY_ALPHA, default)

GPIO	Function	Connection
0–15	SLOT 0–15 (configurable)	Any sensor type: DS18B20, DHT22, or BME280
22	PIO	Passive Buzzer (+)
26	I2C1 SDA	LCD SDA (PCF8574 backpack)
27	I2C1 SCL	LCD SCL (PCF8574 backpack)

Note: Uses I2C1 bus on GPIO 26/27 — keeps GPIO 0-15 free for sensors. PCF8574 backpack at address 0x27 (default). Set -DHD44780_I2C_ADDR=0x3F in build flags if your backpack uses the alternative address. I2C pull-up resistors (4.7 kΩ) are built into the backpack — no external resistors needed. All 16 sensor slots available.

Pin Reference — HD44780 16×2 Parallel (SIMUT_DISPLAY_ALPHA, -DHD44780_MODE_PARALLEL=1)

GPIO	Function	Connection
0–15	SLOT 0–15 (configurable)	Any sensor type: DS18B20, DHT22, or BME280
16	LCD RS (register sel)	HD44780 pin 4
17	LCD EN (enable)	HD44780 pin 6
18	LCD D4 (data bit 4)	HD44780 pin 11
19	LCD D5 (data bit 5)	HD44780 pin 12
20	LCD D6 (data bit 6)	HD44780 pin 13
21	LCD D7 (data bit 7)	HD44780 pin 14
22	PIO	Passive Buzzer (+)

All 16 sensor slots available — display uses GPIO 16-21 (SPI0 pins, free in alpha build). LCD VCC (pin 2) and contrast (VO, pin 3 via 10 kΩ pot) connect to 5V. R/W (pin 5) connects to GND.

Power

• Power the Pico W via USB (5 V)
• TFT display and sensors powered from Pico W’s 3V3 pin
• HD44780 LCD powered from 5V (VBUS pin or external) — do not use 3V3 for the LCD
• PCF8574 I2C backpack has its own 3.3V regulator — power from 5V
• BME280 sensor module powered from 3V3
• Average consumption: 80–120 mA @ 5 V (TFT display active, WiFi connected)
• Peak consumption: ~250 mA (telemetry burst + TFT render)
• HD44780 consumption: ~20 mA (backlight off) to ~80 mA (backlight on)

Wiring Checklist — ILI9341 TFT

• All DS18B20 sensors have 4.7 kΩ pull-up resistor on data line to 3V3
• BME280 modules have I2C pull-ups (usually built-in; verify with multimeter)
• TFT shares SPI bus with Touch controller (separate CS pins: GPIO 28 for TFT, GPIO 17 for Touch)
• Common ground between Pico W, display, and all sensors
• Passive buzzer connected between GPIO 22 and GND (no resistor needed — PIO-driven)
• Use quality USB cable (>=22 AWG) — voltage drops cause reboots
• Configure slots via CLI before physical wiring — use gpio to see the resource map

Wiring Checklist — HD44780 I2C

• LCD VCC powered from 5V (VBUS or external), not 3V3
• PCF8574 backpack SDA → GPIO 26, SCL → GPIO 27
• I2C address matches build flag (default 0x27, alternative 0x3F)
• All 16 sensor slots available (GPIO 0-15 untouched)
• All DS18B20 sensors have 4.7 kΩ pull-up resistor on data line to 3V3
• Common ground between Pico W, LCD backpack, and all sensors
• Passive buzzer connected between GPIO 22 and GND

Wiring Checklist — HD44780 Parallel

• LCD VCC (pin 2) powered from 5V, not 3V3
• LCD VO (pin 3) → 10 kΩ potentiometer wiper (ends to 5V and GND) for contrast
• LCD R/W (pin 5) → GND
• LCD RS (pin 4) → GPIO 16, EN (pin 6) → GPIO 17
• LCD D4 (pin 11) → GPIO 18, D5 (pin 12) → GPIO 19
• LCD D6 (pin 13) → GPIO 20, D7 (pin 14) → GPIO 21
• All 16 sensor slots available (GPIO 0-15 untouched)
• All DS18B20 sensors have 4.7 kΩ pull-up resistor on data line to 3V3
• Common ground between Pico W, LCD, and all sensors
• Passive buzzer connected between GPIO 22 and GND

---

Display Mode Comparison

Pin	ILI9341 TFT (default)	HD44780 I2C (alpha)	HD44780 Parallel (alpha)
GPIO 0–15	SLOT 0–15 (configurable)	SLOT 0–15 (configurable)	SLOT 0–15 (configurable)
GPIO 16	SPI0 MISO	—	LCD RS
GPIO 17	Touch CS	—	LCD EN
GPIO 18	SPI0 SCK	—	LCD D4
GPIO 19	SPI0 MOSI	—	LCD D5
GPIO 20	Touch IRQ	—	LCD D6
GPIO 21	—	—	LCD D7
GPIO 22	Buzzer	Buzzer	Buzzer
GPIO 26	TFT RST	SDA (I2C1)	—
GPIO 27	TFT DC	SCL (I2C1)	—
GPIO 28	TFT CS	—	—
Max sensors	Up to 16 (type-dependent)	Up to 16 (type-dependent)	Up to 16 (type-dependent)
Build flag	(default)	-DSIMUT_DISPLAY_ALPHA=1	-DSIMUT_DISPLAY_ALPHA=1 -DHD44780_MODE_PARALLEL=1

Design rule: GPIO 0-15 are reserved for sensors. All display functions use GPIO 16+ only. This ensures zero conflicts — every display mode supports the full sensor slot complement. Each slot is configurable via CLI before physical assembly — slots are no longer fixed to a specific sensor type.

HD44780 Pinout Reference

HD44780 Pin	Symbol	I2C Mode	Parallel Mode
1	VSS	GND	GND
2	VDD	5V (via backpack)	5V
3	VO	Contrast (backpack pot)	10 kΩ pot wiper
4	RS	—	GPIO 16
5	R/W	GND (via backpack)	GND
6	EN	—	GPIO 17
7	D0	—	—
8	D1	—	—
9	D2	—	—
10	D3	—	—
11	D4	—	GPIO 18
12	D5	—	GPIO 19
13	D6	—	GPIO 20
14	D7	—	GPIO 21
15	LED+	5V (via backpack, jumper)	5V (via 100 Ω resistor)
16	LED-	GND (via backpack, jumper)	GND

See User Manual for complete hardware setup instructions.