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Make an infrared rangefinder with ESP8266

TUTORIAL

Learn to use I^2 C to add hardware to your microcontrollers

Make an infrared

rangefinder with ESP8266

ost robotics projects need to

measure distance for navigation,

but distance measurement is

also necessary for other projects

such as camera focusing and

surface level determination. In

this project an infrared laser rangefinder is used to

measure target distance, with the results shown

on an OLED display. The rangefinder and the OLED

display are available budget-priced, as adapter boards,

only requiring I^2 C signals and power. The heart of the

device is a NodeMCU embedded-computer board,

using the ESP8266 processor.

The VL53L0X infrared laser rangefinder is more

accurate and has a much smaller sensing element

than the popular ultrasonic rangefinder, the HR-SC04,

and is almost as cheap.

The ESP8266 is a very useful

processor and this project

provides a practical introduction

to using it. The NodeMCU board

is a great board to start with, as

it has all the ancillary components

and a USB interface to allow

it to be programmed straight

out of the box. The same

code and interface wiring can

be used in a final project based

on a raw ESP12E, for even lower

cost and power consumption.

ASSEMBLING

THE HARDWARE

The black and white 0.96”, 128 × 64

pixel, OLED display has graphics and text

capability. It connects to the host processor

via the I^2 C interface. Modules are available,

ready to plug into a breadboard.

The IR rangefinder VL53L0X sensor module,

from ST Microelectronics, is tiny, but several

suppliers provide breakout boards. It has a range of

1.5 metres, runs off 3.3 V and, like the OLED module,

connects via an I^2 C interface. The XSHUT terminal

can be used to put this module into low-power mode,

when measurements are not being taken.

The same I^2 C interface can be used for both

modules, minimising the GPIOs used, as they have

different addresses, 0x52 for the IR rangefinder and

0x3C for the OLED display.

The NodeMCU board is almost too wide for a

standard breadboard, but can easily be mounted

on two mini-breadboards to allow connection to

the modules, as shown in the photograph and

Figure 1 diagram.

The two modules are connected to the NodeMCU

via the I^2 C interface. To use this interface, connect

the two signal lines, SDA and CLK, power lines and

let the ESP8266 version of the wire.h library in the

Arduino IDE handle all the details.

The ESP8266 can be set up to use almost any pair

of GPIO pins to form an I^2 C bus. Here D3(GPIO0) is

used as the SDA line and D2(GPIO2) as the SCL line,

as these lines already have pull-up resistors fitted on

the NodeMCU.

CONNECTING EVERYTHING TOGETHER

All three modules are plugged into a breadboard and

wired up with links, as shown in Figure 1.

The NodeMCU already has pull-up resistors on

D3(GPIO0) and D2(GPIO2), so only wire links to the

OLED and IR rangefinder modules are required. The

XSHUT connection on the IR rangefinder module is

also shown connected to D5(GPIO14).

The NodeMCU provides the power for the display

and sensor modules via the +3.3 V connections,

enabling the whole circuit to be powered from the PC

over the USB or a USB battery pack.

SETTING UP THE ARDUINO IDE FOR USE

WITH ESP8266 BOARDS

The simplest way to program ESP8266 boards is via

the Arduino IDE. The core Arduino IDE package must

M

Bill Grainger

Bill Grainger is a

physicist and design

engineer who loves

coding and having

computers interact

with the real world. He

works with wind energy

on all scales and enjoys

running, sea kayaking,

and mountaineering.

Below

VL53LOX IR laser

rangefinder on

breakout board