What is ToF and How to Use It?

Time-of-Flight (ToF) is a method of distance measurement that calculates how long it takes for a signal (usually a light or laser pulse) to travel to a target and back to the sensor. The ToF HAT uses this principle with a laser light source and highly sensitive detectors to calculate the distance with high accuracy.

1. Light Emission: The sensor emits a laser pulse.

2. Reflection: The pulse reflects off a target object.

3. Time Measurement: The sensor records the time it took for the light to return.

4. Distance Calculation: Using the speed of light and the time it takes for the pulse to return, the sensor calculates the distance to the object.

This method of distance measurement is highly accurate and operates independently of surface reflectivity, a significant advantage over traditional ultrasonic sensors.

 

How to Use The ToF Hat

Materials required

• M5StickCPlus2: Acts as the core controller and is responsible for displaying data

• M5StickC ToF HAT: High-precision laser distance sensors for distance measurement

import os, sys, io
import M5
from M5 import *
from hardware import *
from hat import ToFHat

label0 = None
label1 = None
i2c0 = None
pin19 = None
pwm2 = None
hat_tof_0 = None

def setup():
  global label0, label1, i2c0, pin19, pwm2, hat_tof_0

  M5.begin()
  label0 = Widgets.Label("label0", 0, 0, 1.0, 0xffffff, 0x222222, Widgets.FONTS.DejaVu18)
  label1 = Widgets.Label("label1", 100, 0, 1.0, 0xffffff, 0x222222, Widgets.FONTS.DejaVu18)

  Widgets.setRotation(1)
  i2c0 = I2C(0, scl=Pin(26), sda=Pin(0), freq=100000)
  hat_tof_0 = ToFHat(i2c0)
  pin19 = Pin(19, mode=Pin.OUT)
  pwm2 = PWM(Pin(2), freq=5000, duty=512)

def loop():
  global label0, label1, i2c0, pin19, pwm2, hat_tof_0
  M5.update()
  label0.setColor(0x33ff33, 0x000000)
  label1.setColor(0x33ff33, 0x000000)
  label0.setText(str('distance'))
  label1.setText(str(hat_tof_0.get_distance()))
  if (hat_tof_0.get_distance()) < 10:
    pin19.value(1)
    pwm2.duty(512)
  else:
    pin19.value(0)
    pwm2.duty(0)

if __name__ == '__main__':
  try:
    setup()
    while True:
      loop()
  except (Exception, KeyboardInterrupt) as e:
    try:
      from utility import print_error_msg
      print_error_msg(e)
    except ImportError:
      print("please update to latest firmware")

Copy Code ✔ Copied!

Initialize the IIC, hat, set GPIO19 to output mode to control the light on/off, and set GPIO2 to PWM frequency, and duty cycle to control the buzzer.

Display the distance measured on the M5stickCplus2 and set the distance at which you would like to have a warning.

The M5StickC ToF HAT is an I2C-based sensor module that can be easily connected to the M5StickC device. Here are the key components of the module:

   

Power Supply:

Distance Calculation:

  The sensor calculates the distance by using the formula:

  Distance=c×t2\text{Distance} = \frac{c \times t}{2}Distance=2c×t

  where:

Using M5StickC ToF HAT in Projects

To integrate the M5StickC ToF HAT with the M5StickC device:

1. Hardware Setup:

• Plug the ToF HAT into the I2C port of the M5StickC. The M5StickC will automatically power and communicate with the ToF sensor through the I2C bus.

2. Programming:

• Alternatively, you can use Arduino IDE or MicroPython to write custom code, allowing for more control and flexibility in your projects.
• You can use UIFlow, the graphical programming platform, to interact with the sensor and read the distance values. UIFlow makes it easy to program the M5StickC and access the ToF sensor's data with just a few blocks.

3. Example UIFlow Block Program:

• In UIFlow, you can use blocks to initialize the sensor, read the distance, and display the result on the screen or take action based on the measured distance.

4. Data Processing:

• Once you’ve retrieved the distance data, you can process it and trigger actions. For example:
  • If the distance is less than a threshold, activate a buzzer or sound an alarm.
  • If you're building a robot, change its direction when an obstacle is detected.

      

Conclusion

The M5StickC ToF HAT is a powerful and easy-to-integrate sensor that brings high-precision distance measurement to your projects. Whether you're developing a robot obstacle avoidance system, a proximity sensor, or a vehicle reversing radar, this ToF sensor offers a simple solution with high accuracy and reliability. With low power consumption and the ability to work in a variety of lighting and surface conditions, it's an excellent tool for both hobbyists and professionals working on M5StickC-based projects.