From a30877fd3d6b484bd15548eee3c3091bf510967f Mon Sep 17 00:00:00 2001
From: Laurens Valk <laurens@pybricks.com>
Date: Fri, 10 Jul 2020 14:22:07 +0200
Subject: [PATCH] official_models/pup/trains_sensors: tilt project

This adds a project that shows how you can combine LEGO trains with the
Powered Up Tilt Sensor to detect slopes in a train track.
---
 .../trains_sensors/slope_detection/README.md  | 32 +++++++++++++++++
 .../trains_sensors/slope_detection/slope.py   | 35 +++++++++++++++++++
 2 files changed, 67 insertions(+)
 create mode 100644 official_models/pup/trains_sensors/slope_detection/README.md
 create mode 100644 official_models/pup/trains_sensors/slope_detection/slope.py

diff --git a/official_models/pup/trains_sensors/slope_detection/README.md b/official_models/pup/trains_sensors/slope_detection/README.md
new file mode 100644
index 0000000..1effbf8
--- /dev/null
+++ b/official_models/pup/trains_sensors/slope_detection/README.md
@@ -0,0 +1,32 @@
+# Rail slope detection
+
+Made by: The Pybricks Authors
+
+## Introduction
+
+This project shows how you can integrate the
+[Tilt Sensor](https://docs.pybricks.com/en/latest/pupdevices.html#tilt-sensor)
+in your LEGO trains. You can use this sensor to detect a slope in the rail
+track.
+
+## Demo
+
+This program makes the train drive until it detects a slope of 8 degrees or
+more. Then it drives back down. You can watch a video
+[here](https://www.youtube.com/watch?v=Wc0mRIBjhIU).
+
+## Requirements
+- Generic LEGO train, such as 60197 or 60198
+- Powered Up [Tilt Sensor](https://docs.pybricks.com/en/latest/pupdevices.html#tilt-sensor)
+
+## Building instructions
+Build the train using the standard instructions. Mount the Tilt Sensor anywhere
+on the train. See the video for an example. Mount it horizontally. The side
+with the cable should face towards the front: in the direction of driving.
+
+## Ports
+- Train motor on port A 
+- Tilt sensor on port B
+
+## Programming and running instructions
+The train must start on a horizontal track. Then run the program.
diff --git a/official_models/pup/trains_sensors/slope_detection/slope.py b/official_models/pup/trains_sensors/slope_detection/slope.py
new file mode 100644
index 0000000..4615d0a
--- /dev/null
+++ b/official_models/pup/trains_sensors/slope_detection/slope.py
@@ -0,0 +1,35 @@
+from pybricks.pupdevices import TiltSensor, DCMotor
+from pybricks.parameters import Port
+from pybricks.tools import wait
+
+# Initialize the train motor.
+# If you have a motor with encoders, use the Motor class instead.
+train = DCMotor(Port.A)
+
+# Initialize the tilt sensor.
+sensor = TiltSensor(Port.B)
+
+# Measure the tilt while the train is on a flat surface.
+pitch_start, roll_start = sensor.tilt()
+
+# Start driving.
+train.dc(-50)
+
+# We need to reach a constant speed before we can check tilt again,
+# because acceleration affects tilt. So we wait a second.
+wait(1000)
+
+# Wait for the train to sense the hill.
+while True:
+    pitch_now, roll_now = sensor.tilt()
+
+    wait(10)
+
+    # If we reached an extra 3 degrees, exit/break the loop.
+    if pitch_now >= pitch_start + 8:
+        break
+
+# Drive backwards for a few seconds and then stop.
+train.dc(40)
+wait(3000)
+train.dc(0)