# Hardware Wiring Guide Wiring diagrams for ESP32 TTGO T-Call v1.4 with RS485 Modbus connection to Acuvim II power meter, optional SD card module, and GSM antenna. --- ## ESP32 TTGO T-Call v1.4 Pinout (Relevant Pins) ``` ┌──────────────┐ │ TTGO T-Call │ │ v1.4 │ 3V3 ───┤ 3V3 VIN ├─── 5V GND ───┤ GND GND ├─── GND ┤ GPIO36 GPIO23├─── SPI MOSI (SD) ┤ GPIO39 GPIO22├─── ┤ GPIO34 GPIO1 ├─── TX0 (USB Serial) ┤ GPIO35 GPIO3 ├─── RX0 (USB Serial) ┤ GPIO32 GPIO21├─── ┤ GPIO33 GPIO19├─── SPI MISO (SD) ┤ GPIO25 GPIO18├─── SPI SCK (SD) RS485 DE/RE ───┤ GPIO4 GPIO5 ├─── SD CS ┤ GPIO0 GPIO17├─── TX2 (RS485 DI) ┤ GPIO2 GPIO16├─── RX2 (RS485 RO) ┤ GPIO15 GPIO14├─── ┤ GPIO13 GPIO12├─── └──────────────┘ Built-in SIM800L: GPIO26 (TX), GPIO27 (RX) Built-in SIM slot on bottom of board ``` **Note:** The TTGO T-Call v1.4 has SIM800L built into the board. No external GSM module wiring is needed. --- ## RS485 Module Connection (MAX485 / MAX3485) Connect the ESP32 to an RS485 transceiver module, then to the Acuvim II. ### Wiring Table | RS485 Module Pin | ESP32 Pin | Description | |------------------|-----------|-------------| | DI (Data In) | GPIO17 (TX2) | UART2 transmit | | RO (Receiver Out) | GPIO16 (RX2) | UART2 receive | | DE (Driver Enable) | GPIO4 | Direction control | | RE (Receiver Enable) | GPIO4 | Direction control (active low, tied to DE) | | VCC | 3.3V | Power supply | | GND | GND | Ground | | A | Acuvim II A (+) | RS485 bus positive | | B | Acuvim II B (-) | RS485 bus negative | ### Wiring Diagram ``` ESP32 TTGO T-Call MAX485 Module Acuvim II ┌─────────────────┐ ┌──────────────┐ ┌────────────┐ │ │ │ │ │ │ │ GPIO17 (TX2) ───┼──────────┤ DI A ├──────────┤ A (+) │ │ │ │ │ │ │ │ GPIO16 (RX2) ───┼──────────┤ RO B ├──────────┤ B (-) │ │ │ │ │ │ │ │ GPIO4 ──────────┼────┬─────┤ DE │ │ GND ───────┤ │ │ └─────┤ RE │ │ │ │ │ │ │ │ │ │ 3V3 ───────────┼──────────┤ VCC │ │ │ │ │ │ │ │ │ │ GND ───────────┼──────────┤ GND │ │ │ │ │ │ │ │ │ └─────────────────┘ └──────────────┘ └────────────┘ ``` **DE and RE tied together:** GPIO4 drives both pins. HIGH = transmit mode, LOW = receive mode. The firmware toggles this automatically during Modbus transactions. --- ## Acuvim II RS485 Terminal Block The Acuvim II has an RS485 terminal block on the bottom of the meter. ``` Acuvim II Bottom Terminal Block ┌─────────────────────────────────┐ │ ... │ A (+) │ B (-) │ GND │ ...│ └─────────────────────────────────┘ ``` - **A (+):** Connect to MAX485 module A pin - **B (-):** Connect to MAX485 module B pin - **GND:** Connect to common ground with ESP32 ### Acuvim II Modbus Settings Configure on the meter's front panel: - **Protocol:** Modbus RTU - **Address:** 1 (default, configurable 1-247) - **Baud Rate:** 9600 (default, configurable) - **Parity:** None - **Stop Bits:** 1 --- ## SD Card Module Connection (Optional) For offline buffering, connect a standard SPI SD card module. | SD Module Pin | ESP32 Pin | Description | |---------------|-----------|-------------| | MOSI | GPIO23 | SPI Master Out Slave In | | MISO | GPIO19 | SPI Master In Slave Out | | SCK | GPIO18 | SPI Clock | | CS | GPIO5 | Chip Select | | VCC | 3.3V | Power (use 3.3V modules only) | | GND | GND | Ground | ``` ESP32 TTGO T-Call SD Card Module ┌─────────────────┐ ┌──────────────┐ │ │ │ │ │ GPIO23 (MOSI) ──┼──────────┤ MOSI 3V3 ├─── 3V3 │ │ │ │ │ GPIO19 (MISO) ──┼──────────┤ MISO GND ├─── GND │ │ │ │ │ GPIO18 (SCK) ───┼──────────┤ SCK │ │ │ │ │ │ GPIO5 (CS) ─────┼──────────┤ CS │ │ │ │ │ └─────────────────┘ └──────────────┘ ``` Use a micro SD card formatted as FAT32. The firmware creates the `/telemetry/` directory on first use. --- ## SIM Card Insertion The TTGO T-Call v1.4 has a SIM card slot on the bottom of the board. ``` Bottom of TTGO T-Call v1.4 ┌─────────────────────────────┐ │ │ │ ┌─────────────────┐ │ │ │ SIM Card Slot │ │ │ │ (micro SIM) │ │ │ │ Insert with │ │ │ │ contacts DOWN │ │ │ └─────────────────┘ │ │ │ └─────────────────────────────┘ ``` - Use a **micro SIM** (not nano — use adapter if needed) - Insert with contacts facing **down** toward the PCB - SIM must have data plan enabled - SIM PIN must be disabled (or configure PIN in firmware) --- ## GSM Antenna The TTGO T-Call v1.4 has an IPX (U.FL) connector for the GSM antenna. - Attach the supplied GSM antenna to the IPX connector - For better signal in metal enclosures, use an external antenna with SMA connector and IPX-to-SMA pigtail - Position antenna away from the ESP32 and RS485 module to reduce interference --- ## Power Supply ### USB Power (Development) Connect micro-USB cable to the TTGO T-Call. Provides 5V via USB. ### External Power (Production) | Parameter | Value | |-----------|-------| | Input voltage | 5V DC (via VIN pin) | | Current requirement | 500mA minimum (GSM peaks at 2A) | | Recommended supply | 5V 2A regulated DC adapter | For GSM operation, a supply capable of 2A peak current is required due to SIM800L transmission bursts. ``` DC Power Supply ESP32 TTGO T-Call ┌──────────────┐ ┌──────────────────┐ │ │ │ │ │ +5V ─────────┼────────────┤ VIN │ │ │ │ │ │ GND ─────────┼────────────┤ GND │ │ │ │ │ └──────────────┘ └──────────────────┘ ``` **Do not power via USB and VIN simultaneously** unless the USB is only for serial monitoring. --- ## Complete Wiring Diagram ``` ESP32 TTGO T-Call v1.4 ┌───────────────────────┐ │ │ ┌─────────┐ GPIO17 (TX2)──┤ 3V3──┼──┐ │ MAX485 ├──DI │ │ │ │ │ │ GND──┼──┼──┐ │ ├──RO──GPIO16 (RX2)┤ │ │ │ │ │ │ [SIM800L BUILT-IN] │ │ │ │ ├──DE──GPIO4───────┤ [SIM SLOT BOTTOM] │ │ │ │ ├──RE──┘ │ │ │ │ │ │ │ GPIO23───┼──┼──┼──MOSI──┐ │ VCC───┼──────────────────┼── 3V3 │ │ │ │ │ GND───┼──────────────────┼── GND GPIO19───┼──┼──┼──MISO─┤ SD Card │ │ │ GPIO18───┼──┼──┼──SCK──┤ Module │ A────┼──Acuvim A (+) │ GPIO5────┼──┼──┼──CS───┤ │ B────┼──Acuvim B (-) │ │ │ │ VCC──┘ └─────────┘ │ │ └──┼──GND │ VIN──────┼──5V │ GSM Antenna ─────IPX─┤ │ │ └───────────────────────┘ │ │ ┌─────────────────┐ │ │ Acuvim II │ │ │ RS485 Terminal │ │ │ A (+) ├─ MAX485 A│ │ B (-) ├─ MAX485 B│ │ GND ├──────────┘ └─────────────────┘ ``` --- ## Cable Recommendations | Connection | Cable Type | Max Length | |------------|-----------|-----------| | RS485 (ESP32 to Acuvim) | Shielded twisted pair (STP), 22-24 AWG | 1200m | | SPI (ESP32 to SD) | Short jumper wires | 15cm | | USB (development) | Micro-USB data cable | 2m | | Power (production) | 22 AWG stranded | 3m | For RS485 runs over 10m, use 120 ohm termination resistors at each end of the bus.