About The Line Following Module

The robot comes equipped with a 4 channel IR module attached to the bottom of the robot. There are LEDs on top of the module that indicate the state of the sensors automatically without the need to write any code.

From the datasheet

Infrared sensor data:

  • Address: 0x0A
  • Type: Read
  • Range: 0x0-0xF
  • Additional Info:
    • 1 bit = 1 sensor state
    • 0 means LED is lit, 1 means LED is off
    • If we label sensors from left to right accordingly: s1, s2, s3, s4; then output byte corresponds to: s2, s1, s3, s4

Label sensors from left to right: s1, s2, s3, s4; respectively

So if we get an output 0b0101 Then:

\(2^3\) \(2^2\) \(2^1\) \(2^0\)
s2 s1 s3 s4
0 1 0 1

Then that implies: - s1: LED off - s2: LED lit - s3: LED lit - s4: LED off

To get the value of a certain bit, for instance this \(\text{0b1}\underline{1}\text{01}\)

  1. Shift to the right by \(n\) where \(n\) is the amount of places to the left of lowest bit (or \(2^n\) in base 10). meaning 0b1101 >> 2 results in 0b11.
  2. Remove all bits to the left by using the AND operation with 0b1. 0b11&0b01 outputs 1 which is exactly the binary digit we're trying to retrieve.

Calibrating The Sensors

To correctly output the right value based on your surroundings, we need to calibrate the sensors. Place all the sensors over a black material and adjust accordingly: 1. Turn all the knob until no LED lights up 2. Turn all the knobs until LED lights up and keep it there

  1. remove to surface
  2. check that LED doesn't light up

Reading Data From Sensor

reg = 0x0A
desired_blocks_of_data = 1
track_data = bot.read_data_array(reg, desired_blocks_of_data)

Formatting the data

Pulling data out from the list and converting to int type

track_data = int(track_data[0])

If we convert it to binary, we get an output as such:

0b1011

reg = 0x0A
desired_blocks_of_data = 1
w_for_ir = widgets.Text(
    description='State: ',
    disabled=True   
)

display(w_for_ir)
while True:
    track_data = bot.read_data_array(reg, desired_blocks_of_data)[0]
    w_for_ir.value = bin(track_data)