07_driving_base_input.md

Drive Base as Sensor

- learn to read how far the dirve base has traveled
- learn to read how much the drive base has turned
- learn to read the measurement of the drive base travelling on a curve
- learn to reset the drive base values

:class: important
To explore all Pybricks' features check the **[Pybricks documentaion](https://docs.pybricks.com/en/stable/index.html)**. This can also be seen in the right-hand panel of the Pybricks IDE.

Since the drive base is made up of motors, the encoders can also be used to measure what the robot has done.

Drive Base Measurement Functions

There are three functions that can extract measurements from the drive base:

• distance()→ int: mm → Gets the estimated driven distance (mm).
• angle()→ int: deg → Gets the estimated rotation angle (deg) of the drive base.
• state()→ Tuple[int, int, int, int] → Gets the state of the robot. The return tuple is (distance, speed, angle, turn_rate)

There is also one configuration function:

• reset() → Resets the estimated driven distance and angle to 0.

Drive Base Measurement Example

Now use the code below to explore these functions:

1. Create a new file called drive_base_inputs.py
2. Type the code below into the file
3. Predict what you think will happen.
4. When running your code you will need to interact with the robot:
   • to get an arc movement reading, press the left button
   • to get a straight line distance reading, press the right button
   • to get a turn degrees reading, press the Bluetooth button

:linenos:

- **lines 3 - 7** → imports all the Pybricks command for use with your robot
- **line 10** → initialises the hub
- **lines 12 - 14** → initialises the drive base
- **line 16** → sets the robot's distance and angle counters to `0`
- **line 19** → create the main loop
- **line 20** → checks for pressed buttons and stores them in `pressed`
- **line 22** → checks if the left button was pressed
- **line 23** → get the robot's state tuple and stores the values in `distance`, `speed`, `angle`, and `rate_of_turn`
- **line 24** → prints the robot state values stored in `distance`, `speed`, `angle`, and `rate_of_turn`
- **line 25** → drives the robot in an arc
- **line 26** → get the robot's state tuple and stores the values in `distance`, `speed`, `angle`, and `rate_of_turn`
- **line 27** → prints the robot state values stored in `distance`, `speed`, `angle`, and `rate_of_turn`
- **line 29** → checks if the right button is pressed
- **line 30** → reads the current robot distance count and stores it in `distance`
- **line 31** → prints th current robot distance count
- **line 32** → moves the robot in a straight line
- **line 33** → reads the current robot distance count and stores it in `distance`
- **line 34** → prints th current robot distance count
- **line 36** → checks if the Bluetooth button is pressed
- **line 37** → reads the current robot angle count and stores it in `angle`
- **line 38** → prints th current robot angle count
- **line 39** → turns the robot
- **line 40** → reads the current robot angle count and stores it in `angle`
- **line 41** → prints th current robot angle count
- **line 43 - 44** → if not button is pressed stop the drive base

:class: caution
- what happens if you move line 16 to inside the main loop?
- can you use `my_robot.state()` to measure a straight move by the robot?