brickpipe 0.2.0

A json IPC interface for interacting with pybricks hubs

BrickPipe

Brickpipe provides a JSON-based Inter-Process Communication (IPC) interface to interact with Pybricks hubs. It communicates via standard input (stdin) for commands and standard output (stdout) for events.

Each message (incoming or outgoing) must be a single-line JSON object.

Message Format

All messages are JSON objects that contain an event_type field.

{
  "event_type": "event_name",
  "other_field": "value"
}

---

Incoming Events (Commands)

These commands are sent to the script via stdin.

event_type	Parameters	Description
start_ble_scanning	timout : int | float (required)	Begins bluetooth scanning with a specified timeout.
connect_to_hub	conn_type: "ble" or "usb" (required) ble_address: string (optional) ble_hub_name: string (optional)	Connects to a hub. ble_address and ble_hub_name are used for filtering bluetooth hubs.
disconnect_from_hub	None	Disconnects the currently connected hub.
recompile_download	program_path: string (required)	Stops any running program, recompiles the specified Python file, and downloads it to the hub.
recompile_run	program_path: string (required)	Stops any running program, recompiles, downloads, and then starts the program.
run_stored	None	Stops any running program and starts the program already stored in the hub.
send_string	string: string (required)	Sends a string to the hub's stdin.
cancel_running_program	None	Stops the user program currently running on the hub. This has no effect if a program is not running.
exit	None	Disconnects any active hub and terminates the process.

---

Outgoing Events

These events are sent from the script via stdout.

event_type	Payload Fields	Description
ble_device_found	device_name: string address: string rssi: int	Found a hub from scanning. Also triggered by an rssi update when scanning.
hub_connected	None	Successfully established a connection with a hub.
connection_timeout	None	Failed to find or connect to a hub.
download_progress_update	percentage: float (0.00 - 100.00)	Indicates the current progress when downloading a program onto the hub.
program_started	None	A user program has started running on the hub.
program_complete	None	The user program has finished running or was stopped.
hub_printed_line	line: string	A line of text output from the hub (stdout).
compile_error	traceback: string	The Python script failed to compile. Contains the error details.
precondition_violated	explanation: string	The command could not be executed (e.g., missing arguments, or hub not connected).
hub_firmware_outdated	explanation: string	The hub's firmware version is not supported. Can only appear when connecting to a hub.
hub_disconnected	None	The hub has been disconnected (either manually or due to an error).

---

Example Usage

Connecting and Running a Script

1. Connect via bluetooth:

• Input: {"event_type": "connect_to_hub", "conn_type": "ble", "hub_name": "Robot"}
• Output: {"event_type": "hub_connected"}

2. Download and Run a Program:

• Input: {"event_type": "recompile_run", "program_path": "main.py"}
• Output:
  • {"event_type": "download_progress_update", "percentage": 50.0}
  • {"event_type": "download_progress_update", "percentage": 100.0}
  • {"event_type": "program_started"}
  • {"event_type": "hub_printed_line", "line": "Hello, World!"}
  • {"event_type": "program_complete"}

3. Handling a Compile Error:

• Input: {"event_type": "recompile_run", "program_path": "broken.py"}
• Output: {"event_type": "compile_error", "traceback": "..."}