Sensors and readings¶

Sensor objects are created by Robot.configure(). Their read() methods return the latest cached sample without blocking.

Sensor¶

Sensor(port: str, state_mirror=None)

Base class for sensor types. It is public for extension and advanced use, but students normally pass concrete classes to configure() instead of constructing sensors.

Attributes¶

sensor.port: str
sensor.type: str

`read`¶

sensor.read() -> Reading

Returns a base reading. Concrete sensor subclasses return their typed reading.

Reading¶

Reading(timestamp: int, age: float, ok: bool)

Base dataclass shared by every reading.

Field	Type	Meaning
`timestamp`	`int`	Brain sample time in milliseconds
`age`	`float`	Approximate sample age in milliseconds
`ok`	`bool`	Payload is valid and age is at most 250 ms

IMU¶

IMU(port: str, state_mirror=None)
imu.read() -> ImuReading

Nine-axis inertial measurement unit. Heading is relative to the robot's arming pose, not absolute north.

ImuReading¶

ImuReading(
    timestamp: int,
    age: float,
    ok: bool,
    accel_x: float,
    accel_y: float,
    accel_z: float,
    gyro_x: float,
    gyro_y: float,
    gyro_z: float,
    mag_x: int,
    mag_y: int,
    mag_z: int,
    heading: float,
)

Fields	Unit
`accel_x`, `accel_y`, `accel_z`	g
`gyro_x`, `gyro_y`, `gyro_z`	degrees per second
`mag_x`, `mag_y`, `mag_z`	raw integer values
`heading`	degrees relative to arming

reading = robot.imu.read()
if reading.ok:
    print(reading.heading)

RadioBeacon¶

RadioBeacon(port: str, state_mirror=None)
beacon.read() -> RadioBeaconReading

Reads distance reported by a radio beacon.

RadioBeaconReading¶

RadioBeaconReading(
    timestamp: int,
    age: float,
    ok: bool,
    distance_m: float,
)

distance_m is the measured distance in meters.

reading = robot.radiobeacon.read()
if reading.ok and reading.distance_m < 1.0:
    print("Beacon is nearby")

Missing and stale samples¶

Before a sample arrives, typed readings contain zero-valued sensor fields, timestamp == 0, age == math.inf, and ok == False.

After a sample becomes older than 250 ms, its values remain available but ok becomes false. Always check ok before using a reading to command motion.