This lab document describes the SimpleEVSE-WiFi smart EV charger retrofit, an IoT controller upgrade that interfaces an ESP8266 development board (WeMos D1 mini or NodeMCU 1.0) or a dedicated ESP32-based module ("EVSE-WiFi 2.0 Base") with an existing EVSE Wallbox or EVSE DIN electric vehicle charge controller. The ESP microcontroller acts as a Modbus RTU master communicating over TTL UART (at 3.3 V logic levels) to manage the EVSE charging state, set charging current limits, read vehicle and pilot status, authenticate users via an SPI RFID reader, log charge sessions, and read power metrics via Modbus RS485 or S0 pulse metering. The primary power rail powering the microcontroller and RS485 transceiver is 5 V DC (minimum 500 mA), with a 3.3 V DC secondary rail provided by the development board regulator for the ESP core logic, GPIO, and the RC522 RFID reader.

Bill of Materials

Base EVSE Charging Controller

• Identity: EVSE Wallbox or EVSE DIN charge controller board (Simple EVSE WB/DIN). Software revision must be revision 8 (dated 2017-10-31) or higher. Firmware revision 9 is explicitly unsupported due to a vendor firmware bug.
• Quantity needed: 1
• Footprint/package: DIN-rail mount (EVSE DIN) or standalone PCB assembly module (EVSE Wallbox) mounted within an EV charging station enclosure.
• Electrical constraints: Operates from the wallbox internal DC power rail; communicates via 3.3 V/5 V tolerant UART TTL logic pins (TX, RX, GND) and an analog/digital input pin (AN) used to activate Modbus mode during boot.
• Substitution latitude: Must be a Simple EVSE WB or EVSE DIN charge controller running firmware revision 8 or ≥ 10. The system firmware directly maps to Modbus RTU registers specific to this controller (e.g., register 2001 for Modbus enable, registers ≥ 2000 for non-volatile configuration, register writes for vehicle state and charge current). Generic EVSE controllers without this exact Modbus register map will not function.
• Control role: Not a student/user operated control. Set-once configuration during initial setup (AN pin pulled to GND 5 times within 3 seconds at boot to enable Modbus).
• Sourcing plan: retail shopping search: "EVSE Wallbox controller revision 8" or "EVSE DIN ladecontroller"

Main Microcontroller Board (v1.x Hardware Option)

• Identity: ESP8266 Development Board, specifically WeMos D1 mini or NodeMCU 1.0.
• Quantity needed: 1 (if building v1.x variant)
• Footprint/package: Dual-inline breadboard/header module footprint (WeMos D1 mini 1x8 dual headers, pitch 2.54 mm; or NodeMCU 0.9" / 1.0" pitch 2.54 mm).
• Electrical constraints: Power input: 5 V DC at VCC/VIN (draws up to 500 mA peak during Wi-Fi transmission bursts); logic rail: 3.3 V DC; GPIO pins operate strictly at 3.3 V logic levels (GPIO4, GPIO5, GPIO0, GPIO2, GPIO12, GPIO13, GPIO14, GPIO15, GPIO16).
• Substitution latitude: Any WeMos D1 mini or NodeMCU 1.0 ESP8266 development board. Pinout definitions in firmware assume standard ESP8266 GPIO mapping (D1 = GPIO5, D2 = GPIO4, D3 = GPIO0, D4 = GPIO2, D5 = GPIO14, D6 = GPIO12, D7 = GPIO13, D8 = GPIO15, D0 = GPIO16).
• Control role: Reset (RST) tactile button is present on-board for manual reset after flashing.
• Sourcing plan: retail shopping search: "WeMos D1 mini ESP8266 development board"

EVSE-WiFi 2.0 Base Module (v2.0 Hardware Option)

• Identity: EVSE-WiFi 2.0 Base Module (dedicated ESP32-based board, custom board target base_1_045).
• Quantity needed: 1 (alternative to ESP8266 board for v2.0 firmware)
• Footprint/package: Custom enclosed DIN-rail or wallbox-mount adapter module.
• Electrical constraints: 5 V DC input power rail; 3.3 V internal logic rail; 160 MHz ESP32 core clock; 8 MB flash memory.
• Substitution latitude: Proprietary integrated module from evse-wifi.de. If building from source using generic ESP32 hardware, custom pin mapping and partition table definitions (default_8MB.csv) are required.
• Control role: Not an operated control.
• Sourcing plan: retail shopping search: "EVSE-WiFi 2.0 Base Module"

DC Power Supply

• Identity: 5 V DC regulated power supply module (power supply brick or DIN-rail AC/DC power supply).
• Quantity needed: 1
• Footprint/package: Chassis-mount, DIN-rail mount, or encapsulated PCB module (e.g. Mean Well HDR-15-5 or external 5V 1A wall adapter).
• Electrical constraints: Input: 100–240 V AC (or wallbox internal auxiliary DC supply); Output: 5 V DC regulated (±5%), current rating ≥ 500 mA (1 A or higher recommended to prevent Wi-Fi brownouts).
• Substitution latitude: Any 5 V DC regulated power supply rated for ≥ 500 mA continuous output.
• Control role: None (fixed power supply).
• Sourcing plan: distributor lookup (representative example — sources give spec only): Mean Well HDR-15-5

TTL-to-RS485 Transceiver Converter Module

• Identity: UART TTL to RS485 differential converter module (automatic flow control or hardware DE/RE handling, marketed as "EVSE-WiFi TTL-RS485 Converter").
• Quantity needed: 1 (required only if an RS485 Modbus energy meter is installed)
• Footprint/package: Small breakout module with 4-pin TTL header (VCC, GND, TX, RX) and 2-pin screw terminal block (A+, B-).
• Electrical constraints: Supply voltage: 5 V DC; logic I/O: 3.3 V / 5 V TTL compatible; bus side: RS485 differential balanced signaling (A and B lines).
• Substitution latitude: Any TTL-to-RS485 converter module featuring automatic flow control (transceivers with automatic TX/RX switching, e.g. based on MAX13487, MAX485 with auto-direction circuitry, or SP3485). Must operate at 9600 baud.
• Control role: None.
• Sourcing plan: retail shopping search: "TTL to RS485 converter module automatic flow control"

Modbus Electricity Energy Meter (Optional)

• Identity: Eastron SDM120 (single-phase) or Eastron SDM630 (three-phase) Modbus RTU electricity meter.
• Quantity needed: 1 (optional peripheral)
• Footprint/package: DIN-rail mount (SDM120: 1-module 18 mm width; SDM630: 4-module 72 mm width).
• Electrical constraints: AC mains voltage: 230 V AC nominal (SDM120) or 230/400 V AC (SDM630); RS485 Modbus RTU interface configured to 9600 baud, 8 data bits, 1 stop bit, no parity, Slave ID set to "002".
• Substitution latitude: The Modbus readout routines are tailored specifically to the Eastron SDM120 and SDM630 register addresses. Alternative meters cannot be used over Modbus without modifying the source code, though other pulse meters can be connected via the S0 interface instead.
• Control role: Front-panel navigation buttons used during commissioning to configure slave ID 002 and 9600 baud.
• Sourcing plan: distributor lookup: Eastron SDM120 Modbus / Eastron SDM630 Modbus

S0 Pulse Electricity Meter (Optional Alternative to Modbus Meter)

• Identity: Electricity energy meter equipped with an S0 pulse output interface.
• Quantity needed: 1 (optional peripheral)
• Footprint/package: DIN-rail mount energy meter.
• Electrical constraints: S0 pulse output must be an open-collector / dry-contact interface that switches directly to GND. The sources explicitly warn: do NOT connect 3.3 V or 5 V to this interface. S0+ connects to ESP GPIO0 (D3) and S0- connects to GND.
• Substitution latitude: Any standard DIN-rail electricity meter with a passive S0 transistor/optocoupler output capable of sinking the internal/external pull-up current to GND.
• Control role: None during operation.
• Sourcing plan: retail shopping search: "DIN rail kWh meter S0 pulse output"

RFID Reader Module (Optional)

• Identity: RC522 RFID reader/writer module (based on NXP MFRC522 IC).
• Quantity needed: 1 (optional peripheral)
• Footprint/package: PCB module with integrated PCB trace antenna and 8-pin 2.54 mm single-row header (pins used: 3.3V, GND, RST, MISO, MOSI, SCK, SDA/SS).
• Electrical constraints: Supply voltage: 3.3 V DC (strictly 3.3 V; 5 V will damage the MFRC522 IC); SPI bus communication with ESP8266 (SCK = GPIO14, MISO = GPIO12, MOSI = GPIO13, SDA = GPIO15).
• Substitution latitude: Must be an MFRC522-based module. The documentation explicitly states that PN532 and Wiegand-based RFID readers are not supported.
• Control role: User-facing proximity card reader (tap card against module to activate/deactivate charging).
• Sourcing plan: retail shopping search: "RC522 RFID reader module 13.56 MHz SPI"

RFID Media / Transponders (Optional)

• Identity: Mifare Classic 1KB RFID cards, tags, or keyfobs (ISO/IEC 14443 Type A PICC, 13.56 MHz).
• Quantity needed: 1 or more (one per authorized user).
• Footprint/package: Standard ISO card (CR80) or plastic teardrop/round keyfob.
• Electrical constraints: Passive 13.56 MHz RF transponder with 1 KB EEPROM storage; supports ISO 14443A protocol.
• Substitution latitude: Must be Mifare Classic 1KB (13.56 MHz). 125 kHz tags (EM4100) or high-security NFC cards (DESFire, Ultralight) will not work with the existing firmware code base.
• Control role: Handheld credential operated by the user.
• Sourcing plan: retail shopping search: "Mifare Classic 1K RFID 13.56MHz key fob tag"

Pushbutton Switch (Optional)

• Identity: Momentary tactile pushbutton switch, normally open (SPST-NO).
• Quantity needed: 1 (optional peripheral)
• Footprint/package: Panel-mount pushbutton (12 mm, 16 mm, or 19 mm round panel cutout) or PCB tactile switch.
• Electrical constraints: Dry contact switching to GND (connects ESP8266 GPIO2 / D4 to GND); handles logic-level currents (< 1 mA at 3.3 V).
• Substitution latitude: Any momentary normally open push switch.
• Control role: Student/user operated actuator to start/stop the charging process. Actuator style must be momentary pushbutton (not latching toggle/rocker).
• Sourcing plan: retail shopping search: "momentary panel mount pushbutton normally open"

Status Indicator LED (Optional)

• Identity: Standard discrete light emitting diode, 3 mm or 5 mm (with appropriate current-limiting series resistor, e.g. 330 Ω to 1 kΩ, unless integrated).
• Quantity needed: 1 (optional peripheral)
• Footprint/package: Through-hole radial LED or panel-mount indicator.
• Electrical constraints: Driven by GPIO16 (D0) relative to GND. Sinks/sources at 3.3 V logic levels; continuous current must not exceed 12 mA.
• Substitution latitude: Any standard 3 mm or 5 mm indicator LED (green, blue, red, or amber) with a suitable series resistor to limit current.
• Control role: Passive visual indicator.
• Sourcing plan: distributor lookup (representative example — sources give spec only): Lite-On LTL-4223

Wiring and Interconnect Hardware

• Identity: Jumper wires / hookup wire (22–26 AWG) with DuPont headers (female-to-female and female-to-male) and/or stripped wire leads for terminal block clamping.
• Quantity needed: 1 set (approx. 10 to 20 individual conductors).
• Footprint/package: 0.1" (2.54 mm) female/male crimp connectors and bare-wire terminals.
• Electrical constraints: Low-voltage signal and power lines (< 1 A, 5 V / 3.3 V).
• Substitution latitude: Any standard electronic prototyping hookup wire.
• Control role: None.
• Sourcing plan: retail shopping search: "Dupont jumper wire ribbon cable 2.54mm"

Software and network dependencies

Firmware and Build Tools

• PlatformIO Core / Build Environment:

  • Name: PlatformIO
  • Environment base_1_045:
    • Platform: espressif32@3.0.0 (pinned in platformio.ini)
    • Framework: arduino
    • Board target: base_1_045 (custom board manifest not present in workspace)
    • Partitions manifest: default_8MB.csv (referenced in platformio.ini, not present in workspace)
    • CPU frequency: 160000000L (160 MHz)
    • Build flags/options: upload speed 921600; ignored libraries: ESPAsyncUDP, EspSoftwareSerial
  • Environment d1_mini:
    • Platform: espressif8266 (unpinned in platformio.ini)
    • Framework: arduino
    • Board target: d1_mini
    • Build flags: -D PIO_FRAMEWORK_ARDUINO_LWIP2_LOW_MEMORY -Wl,-Map,output.map (pinned in platformio.ini)
    • Ignored libraries: U8g2
  • Check plan: support-status lookup: espressif32 3.0.0; support-status lookup: espressif8266 unpinned

• Arduino IDE Build Toolchain (Alternative to PlatformIO):

  • Name: Arduino IDE
  • Version: not stated ("Please install Arduino IDE if you didn't already")
  • Core: ESP8266 Core for Arduino IDE (repository: https://github.com/esp8266/Arduino)
  • Version: ≥ v2.4.0 (stated in documentation README.md)
  • Plugin: ESP8266FS Uploader (arduino-esp8266fs-plugin from https://github.com/esp8266/arduino-esp8266fs-plugin)
  • Check plan: support-status lookup: ESP8266 Core for Arduino 2.4.0

Software Libraries and Frameworks

• miguelbalboa/MFRC522:

  • Source: PlatformIO Registry / https://github.com/miguelbalboa/rfid
  • Version: unpinned in platformio.ini (both environments) and README.md
  • Check plan: not checkable: unpinned version and no advisory database for Arduino libraries

• bblanchon/ArduinoJson:

  • Source: PlatformIO Registry / https://github.com/bblanchon/ArduinoJson
  • Version: unpinned in platformio.ini (both environments) and README.md
  • Note: ArduinoJson underwent major breaking API changes between v5, v6, and v7; lack of pinning poses a significant build reproducibility risk.
  • Check plan: not checkable: unpinned version

• emelianov/modbus-esp8266:

  • Source: PlatformIO Registry
  • Version: unpinned in platformio.ini (used in base_1_045 and d1_mini)
  • Check plan: not checkable: unpinned version

• plerup/EspSoftwareSerial:

  • Source: PlatformIO Registry / https://github.com/plerup/espsoftwareserial
  • Version: 6.9.0 (pinned in platformio.ini under env:d1_mini); unpinned in README.md
  • Check plan: vulnerability lookup: plerup/EspSoftwareSerial / platformio / 6.9.0

• CurtRod/ModbusMaster (Forked):

  • Source: https://github.com/CurtRod/ModbusMaster
  • Version: not stated (unpinned git repository master branch)
  • Note: The documentation states that this specific fork must be used instead of the upstream 4-20ma/ModbusMaster library, because the standard library triggers an ESP hardware watchdog timer (WDT) reset on Modbus timeout.
  • Check plan: not checkable: unpinned git fork

• ESPAsyncWebServer:

  • Source: https://github.com/me-no-dev/ESPAsyncWebServer
  • Version: not stated (unpinned in README.md)
  • Check plan: not checkable: unpinned version

• ESPAsyncTCP:

  • Source: https://github.com/me-no-dev/ESPAsyncTCP
  • Version: not stated (unpinned in README.md, mandatory dependency for ESPAsyncWebServer)
  • Check plan: not checkable: unpinned version

• ESPAsyncUDP:

  • Source: https://github.com/me-no-dev/ESPAsyncUDP
  • Version: not stated (unpinned in README.md; ignored on ESP32 in platformio.ini)
  • Check plan: not checkable: unpinned version

• NTPClientLib:

  • Source: https://github.com/gmag11/NtpClient/
  • Version: not stated (unpinned in README.md)
  • Check plan: not checkable: unpinned version

• TimeLib:

  • Source: https://github.com/PaulStoffregen/Time
  • Version: not stated (unpinned in README.md, mandatory dependency for NTPClientLib)
  • Check plan: not checkable: unpinned version

• ESP8266Ping:

  • Source: https://github.com/dancol90/ESP8266Ping
  • Version: not stated (unpinned in README.md)
  • Check plan: not checkable: unpinned version

Flashing Utility and Precompiled Binaries

• Name: Windows flashing script (flash.bat) and compiled firmware binaries
• Source: https://www.evse-wifi.de/download/
• Version: not stated
• Check plan: not checkable: closed vendor download page

Network Exposure and Communication Protocols

• Wi-Fi Connectivity:
  • SoftAP Mode: On initial boot or configuration reset, sets up an unencrypted 802.11 b/g/n Wi-Fi Access Point with SSID evse-wifi. No Wi-Fi password is required (open network).
  • Station (Client) Mode: Connects to local 2.4 GHz Wi-Fi WLAN via credentials supplied through the Web UI.
• IP Addressing:
  • Default AP IP: 192.168.4.1
• Listening Ports and Services:
  • Port 80 (HTTP): Serves web management graphical interface and REST HTTP API.
  • Default Web Interface Credentials: username/password is adminadmin (documented in README.md).
  • WebSocket: Integrated into the async web server for push updates.
  • NTP Client: Sends outbound UDP packets on port 123 to synchronize charge session timestamps.
• HTTP REST API Endpoints (all unauthenticated by default or authenticated via web session):
  • GET /getParameters — Returns JSON object with vehicle status, EVSE status, max current, actual current, active power, duration, energy (kWh), mileage, meter reading, and 3-phase currents (currentP1, currentP2, currentP3).
  • GET /getLog — Returns JSON array of recent charging sessions with RFID UID, username, duration, energy, and calculated price.
  • GET /setCurrent?current=<amps> — Sets EVSE maximum charge current (e.g. ?current=16).
  • GET /setStatus?active=<true|false> — Engages or disengages EVSE charging contactor state.
  • GET /doReboot?reboot=true — Triggers a software reset via ESP.restart().

External Downloads and URLs

• https://www.evse-wifi.de/ — Vendor documentation, news, firmware binaries, and online shop.
• https://www.evse-wifi.de/download/ — Download page for compiled .bin firmware and flash.bat flasher.
• https://github.com/CurtRod/SimpleEVSE-WiFi — Upstream project repository containing showcase images and issue tracker.
• https://github.com/CurtRod/ModbusMaster — Required forked Modbus RTU library containing the WDT fix.
• https://github.com/esp8266/arduino-esp8266fs-plugin — SPIFFS file system uploader plugin for Arduino IDE.

Fabrication and Board Constraints

• Custom PCB / Layout Files: None present in the workspace. The design uses standard off-the-shelf breakout modules (WeMos D1 mini / NodeMCU, RC522 reader, TTL-RS485 converter) wired point-to-point via DuPont jumper wires directly to the screw terminals of the EVSE Wallbox/DIN controller.
• Custom Hardware Board Target: The platform configuration references a board definition board = base_1_045 and custom partition table default_8MB.csv for the ESP32 variant; these files are not included in the repository and represent proprietary vendor board support definitions.