LineSensor

The LineSensor class manages Eliobot's 5 infrared line sensors and provides line tracking and calibration functions.

Sensor positions

Position	Index	Pin
Extrême gauche	0	IO10
Milieu gauche	1	IO11
Centre	2	IO12
Milieu droite	3	IO13
Extrême droite	4	IO14

Initialization

The LineSensor class also requires an instance of Motors for tracking and calibration methods.

import board
import pwmio
import analogio
import digitalio
from elio import Motors, LineSensor

# Moteurs
AIN1 = pwmio.PWMOut(board.IO36)
AIN2 = pwmio.PWMOut(board.IO38)
BIN1 = pwmio.PWMOut(board.IO35)
BIN2 = pwmio.PWMOut(board.IO37)
vBatt_pin = analogio.AnalogIn(board.BATTERY)
motors = Motors(AIN1, AIN2, BIN1, BIN2, vBatt_pin)

# Capteurs de ligne
lineCmd = digitalio.DigitalInOut(board.IO33)
lineCmd.direction = digitalio.Direction.OUTPUT

lineInput = [
    analogio.AnalogIn(board.IO10),  # Capteur 0 — extrême gauche
    analogio.AnalogIn(board.IO11),  # Capteur 1 — milieu gauche
    analogio.AnalogIn(board.IO12),  # Capteur 2 — centre
    analogio.AnalogIn(board.IO13),  # Capteur 3 — milieu droite
    analogio.AnalogIn(board.IO14),  # Capteur 4 — extrême droite
]

line_sensor = LineSensor(lineInput, lineCmd, motors)

Methods

get_line(line_pos)

Returns the value of the line sensor at the given position.

The measurement is calculated as the difference between ambient light and reflected light — a high value indicates the presence of a line.

Paramètre	Type	Description
line_pos	int	Index du capteur (0 à 4)

valeur = line_sensor.get_line(2)  # Lecture du capteur central
print(valeur)

follow_line(threshold)

Make Eliobot follow the line using the 5 sensors. The robot advances if the line is under the central sensor, and corrects its trajectory with the other sensors.

Paramètre	Type	Description
threshold	int	Valeur seuil de détection de ligne

while True:
    line_sensor.follow_line(threshold=5000)

Calibration

Use calibrate_line_sensors() to automatically calculate the threshold appropriate for your environment.

calibrate_line_sensors()

Performs automatic calibration of line sensors:

1. Rotates Eliobot in place collecting 30 samples per sensor.
2. Calculates an optimal threshold from the maximum and minimum values.
3. Save the threshold in the config.json file.
4. Realigns Eliobot on the line (central sensor).

line_sensor.calibrate_line_sensors()

The calculated threshold is saved in config.json:

{ "line_threshold": 4823.5 }

update_sensor_values(all_values)

Updates the list of values ​​of all sensors. Used internally by calibrate_line_sensors().

save_calibration_data(threshold) (static method)

Saves the calibration threshold in config.json.

LineSensor.save_calibration_data(5000)

calculate_median(data) (static method)

Calculates the median of a list of values.

median = LineSensor.calculate_median([100, 200, 150, 300, 250])

Complete example — line tracking with calibration

import board
import pwmio
import analogio
import digitalio
import json
from elio import Motors, LineSensor

AIN1 = pwmio.PWMOut(board.IO36)
AIN2 = pwmio.PWMOut(board.IO38)
BIN1 = pwmio.PWMOut(board.IO35)
BIN2 = pwmio.PWMOut(board.IO37)
vBatt_pin = analogio.AnalogIn(board.BATTERY)
motors = Motors(AIN1, AIN2, BIN1, BIN2, vBatt_pin)

lineCmd = digitalio.DigitalInOut(board.IO33)
lineCmd.direction = digitalio.Direction.OUTPUT

lineInput = [
    analogio.AnalogIn(board.IO10),
    analogio.AnalogIn(board.IO11),
    analogio.AnalogIn(board.IO12),
    analogio.AnalogIn(board.IO13),
    analogio.AnalogIn(board.IO14),
]

line_sensor = LineSensor(lineInput, lineCmd, motors)

# Calibration (à faire une seule fois, pose Eliobot sur la ligne)
line_sensor.calibrate_line_sensors()

# Lecture du seuil sauvegardé
with open("config.json") as f:
    config = json.load(f)
threshold = config["line_threshold"]

# Suivi de ligne
while True:
    line_sensor.follow_line(threshold)