What is it?

This is an optical interface to communicate with devices supporting IEC 62056-21 standard, mostly with utility meters like electric meter, water, etc.

The pin arrangement aligns with the layout found in Wemos/Lolin D1 mini boards and their derivatives. That makes it possible to quickly create a complete device communicating with home automation systems like Home Assistant.

The interface can work with different kinds of microcontrollers that use 3.3 V or 5 V logic levels, not just the ESP32.

What you are buying?

• 1 × Assembled and tested optical interface PCB.
• 2 × Female 4P header 2.54 mm raster

Optionally, you can also add Ring Magnet (see below for details).

ESP32 not included.

Pinout

Pins without a label are not connected

Pinout compatible with

• ESP8266 D1 mini
• ESP32 D1 mini
• ESP32 S2 mini
• ESP32 C3 mini

How to connect

Do not cross RX/TX signals.

Arduino

Before uploading the sketch disconnect TX and RX lines.

Raspberry Pi

Specification

• Power: 3.3V-5V
• Logic level: 3.3V or 5V
• Infrared wavelength: 850-940nm
• Transmission: half-duplex
• PCB
  • Diameter: ⌀30mm ±0.2mm
  • Material: FR4
  • Color: Black
  • Thickness: 1.6mm
  • Surface Finish: Lead Free

PCB Dimensions

Magnet

You can optionally add ring neodymium magnet to your order. The size of the magnet perfectly fits the optical interface.

• Outer diameter: ⌀30 mm
• Inner diameter: ⌀15 mm
• Thickness: 2 mm
• Weight: 8 g
• Magnetic material: N38
• Maximum Operating Temperature: 80 °C
• Coating: Ni+Cu+Ni
• Magnetization Direction: along the 2 mm dimension.

Application

Using this PCB you can build a device to remotely read data from meters with the optical interface.

For detailed build description see PiggyMeter project

If you write your own software, keep in mind that the transmitted data will be picked up by the phototransistor, causing an echo effect.

Watch Youtube video how the interface is tested before shipping: https://youtu.be/KEd2jVFpLUc