mdp-raspberrypi

This repository contains the Python scripts for the Raspberry Pi component of the CZ3004 Multi-Disciplinary Project (MDP).

Topology Diagram

Raspberry Pi Message formats

Android to RPi

General

Set robot mode

{"cat": "mode", "value": "manual"}
{"cat": "mode", "value": "path"}

Possible responses:

{"cat": "info", "value": "Robot is now in Path mode."}
{"cat": "info", "value": "Robot is now in Manual mode."}
{"cat": "error", "value": "Robot already in Path mode."}
{"cat": "error", "value": "Robot already in Manual mode."}

Path Mode Commands

The following commands are only valid if the robot is currently operating in the Path mode. If the robot is in the manual mode, the robot will respond with an error.

{"cat": "error", "value": "Robot must be in Path mode to set obstacles."}
{"cat": "error", "value": "Robot must be in Path mode to start robot on path."}

Set obstacles

RPi will make a call to the Algorithms API and store the received commands and path.

The contents of obstacles together with the configured turning radius (settings.py) will be passed to the Algorithm API.
Please refer to the format for the /path endpoint. Reference: https://github.com/CZ3004-Group-28/Algo

{
  "cat": "obstacles",
  "value": {
    "obstacles": [{"x": 5, "y": 10, "id": 1, "d": 2}],
    "mode": "0"
  }
}

Mode:

• 0: indoors
• 1: outdoors

Navigate around obstacle

RPi will make a call to the Algorithms API and store the received commands and path. This path only consists of the steps for navigating around the obstacle.

{"cat": "single-obstacle", "value": {"robot" : {"x" : 10, "y" : 7, "d" : 0},"obstacle" : {"x" : 10, "y" : 10}}}

Start

Signals to the robot to start dispatching the commands (when obstacles were set).

{"cat": "control", "value": "start"}

If there are no commands in the queue, the RPi will respond with an error:

{"cat": "error", "value": "Command queue is empty, did you set obstacles?"}

Manual Mode Commands

The following commands are only valid if the robot is currently operating in the Manual mode. If the robot is in the Path mode, the robot will respond with an error.

{"cat": "error", "value": "Manual movement not allowed in Path mode."}

Movement commands

Movement commands for the manual mode will set the robot moving indefinitely until a STOP command is received.

For example, when the "forward" button is pressed (and held) in the android app, one command FW-- should be sent and this will make the robot move forward forever. When the user lifts the finger from the "forward" button, another command STOP is sent to stop the robot.

{"cat": "manual", "value": "FW--"}
{"cat": "manual", "value": "BW--"}
{"cat": "manual", "value": "TL--"}
{"cat": "manual", "value": "TR--"}
{"cat": "manual", "value": "STOP"}

Capture image and call Image Recognition API

Pi will immediately capture an image using the camera and make a call to the Image Recognition API.

{"cat": "manual", "value": "MANSNAP"}

Start Robot on the Fastest Car Challenge

{"cat": "manual", "value": "WN01"}
{"cat": "manual", "value": "WN02"}

---

RPi to Android

The RPi will send messages to the Android app in the following format:

{"cat": "xxx", "value": "xxx"}

Message categories:

• info: general messages
• error: error messages, usually in response of an invalid action
• location: the current location of the robot (in Path mode)
• image-rec: image recognition results
• mode: the current mode of the robot (manual or path)
• status: status updates of the robot (running or finished)

Image recognition results

{"cat": "image-rec", "value": {"image_id": "A", "obstacle_id":  "1"}}

Location Updates

In Path mode, the robot will periodically notify android with the updated location of the robot.

{"cat": "location", "value": {"x": 1, "y": 1, "d": 0}}

where x, y is the location of the robot, and d is its direction.

Robot Mode

This message is sent to the Android upon the initial Bluetooth connection and subsequent reconnections.

{"cat": "mode", "value": "path"}
{"cat": "mode", "value": "manual"}

---

STM32 to RPi

After every command received on the STM32, an acknowledgement (string: ACK|xxx) must be sent back to the RPi. This signals to the RPi that the STM32 has completed the command, and is ready for the next command.

---

RPi to STM32

The RPi will only send the following commands to the STM32.

Path mode commands

Indoors: High speed forward/backward, with turning radius of 3x1

• FW0x: Move forward x units
• BW0x: Move backward x units
• FL00: Move to the forward-left location
• FR00: Move to the forward-right location
• BL00: Move to the backward-left location
• BR00: Move to the backward-right location

Outdoors: Slow speed forward/backward, with turning radius of 3x1 or 4x2 (configurable in settings.py)

• FS0x: Move forward x units
• BS0x: Move backward x units
• FL20: Move to the forward-left location (turning radius 3x1)
• FR20: Move to the forward-right location (turning radius 3x1)
• BL20: Move to the backward-left location (turning radius 3x1)
• BR20: Move to the backward-right location (turning radius 3x1)
• FL30: Move to the forward-left location (turning radius 4x2)
• FR30: Move to the forward-right location (turning radius 4x2)
• BL30: Move to the backward-left location (turning radius 4x2)
• BR30: Move to the backward-right location (turning radius 4x2)

Manual mode commands

• FW--: Move forward indefinitely
• BW--: Move backward indefinitely
• TL--: Steer left indefinitely
• TR--: Steer right indefinitely
• STOP: Stop all servos

Miscellaneous commands

• ZZ0x: Buzz the buzzer x times

Buzzer

• 1 buzz : Robot Mode changed or Robot finished path
• 2 buzzes: Bluetooth device connected
• 3 buzzes: Bluetooth disconnected
• 4 buzzes: API is down, start command aborted