LEGO Hub Library

[sophiebremer]

It looks like LEGO SPIKE hubs are accessible via USB. So a library for TypeScript similar to the ones for C#.NET and Python is possible.

Here comes some initial findings. After connecting the hub to the Mac, it powers up and provides two serial interfaces to read and send data. You should not use these interfaces in parallel with the SPIKE.app as this can immediately crash macOS on disconnect.

$ ls -alt /dev/ |more
crw-rw-rw-   1 root    wheel           0x9000007 Aug 26 09:54 cu.usbmodem3468355632311
crw-rw-rw-   1 root    wheel           0x9000006 Aug 26 09:53 tty.usbmodem3468355632311
: q

One can connect to the integrated MicroPython of the blinking hub. Note that the blinking on the hub changes to a constant light after connecting.

$ screen /dev/cu.usbmodem3468355632311 115200
MicroPython v1.14-877-g908921d1c on 2021-11-19; LEGO Technic Small Hub with STM32F413xx
{"m":0,"p":[[0, []], [0, []], [0, []], [0, []], [0, []], [0, []], [4, -9, 992], [0, 0, 0], [0, 0, 0], "", 0]}
{"m":2,"p":[8.328, 100, true]}

# Press/Send CTRL C characters
Traceback (most recent call last):
  File "main.py", line 8, in <module>
  File "hub_runtime.py", line 1, in start
  File "event_loop/event_loop.py", line 1, in run_forever
  File "event_loop/event_loop.py", line 1, in step
KeyboardInterrupt:
>>>

# Following are some autocompletes with TAB character
>>> hub.
__class__       __name__        __version__     BACK
BOTTOM          BT_VCP          FRONT           LEFT
RIGHT           TOP             USB_VCP         battery
bluetooth       button          config          file_transfer
info            led             motion          port
power_off       repl_restart    reset           status
supervision     temperature
>>> hub_runtime.
__class__       __name__        start           __file__
BT_VCP          Timer           USB_VCP         hub
init            LightMethods    LinegraphMonitorMethods
MotorMethods    MoveMethods     SoundMethods    WaitMethods
ProgramMethods  HubMethods      DeviceMethods   get_event_loop
initialize_ports                TIMER_PACE_HIGH
error_handler   pop_force_reset
cleanup_slot_list               RTTimer
notify_gesture_event            notify_orientation_event
notify_button_event             RPCProtocol     system
ProgramRunner   runtime         HubUI
__connection_changed


# Some calls
>>> hub.info()
{'device_uuid': '03970000-1D00-3800-0C51-313239353034', 'product_variant': 0, 'usb_pid': 13, 'usb_vid': 1684, 'hardware_version': 'Version_D'}
>>> hub.status()
{'gyroscope': (0, 0, 0), 'accelerometer': (7, -73, 992), 'yaw_pitch_roll': (0, -4, 0), 'position': (0, -4, 0), 'port': {'A': [], 'B': []}}
>>> hub.power_off()
>>>
$

I did not verified it yet, but the interfaces might work out of the box similar to the serial interface of the Raspberry Pi GPIO for the Raspberry Pi Build HAT.

[sophiebremer]

The hub interface differs from the HAT interface.

If one keeps the default hub_runtime.start() running after established connection and sends port 0, it returns

{"m":"runtime_error","p":[[1, 0, 0, 71], "191f3ad", "4.0.0-gecko.7", "VHJhY2ViYWNrIChtb3N0IHJlY2VudCBjYWxsIGxhc3QpOgogIEZpbGUgInByb3RvY29sL3Vqc29ucnBjLnB5IiwgbGluZSAxLCBpbiBfaGFuZGxlX21lc3NhZ2UKVmFsdWVFcnJvcjogc3ludGF4IGVycm9yIGluIEpTT04K", ""]}

Decoding the base64 string leads to

Traceback (most recent call last):
  File "protocol/ujsonrpc.py", line 1, in _handle_message
ValueError: syntax error in JSON

JSON-RPC

The hub seems to expect JSON input unlike the CLI of the HAT. According to https://github.com/nutki/spike-tools/blob/master/spikejsonrpc.py#L44 it is some form of JSON-RPC, though not all commands do work (anymore?). Note that the exact spacing of input has to be followed or a syntax error occurs.

get_firmware_info Error

Send:

{"m": "get_firmware_info", "p": {}, "i": "6219"}

Response:

{"i":"6219","e":"eyJtZXNzYWdlIjogImdldF9maXJtd2FyZV9pbmZvIiwgInR5cGUiOiAiVU5LTk9XTl9NRVRIT0QifQ=="}

Decoding:

{"message": "get_firmware_info", "type": "UNKNOWN_METHOD"}

get_storage_status Success

Send:

{"m": "get_storage_status", "p": {}, "i": "8293"}

Response:

{"i":"8293","r":{"storage": {"available": 2420, "total": 3072, "pct": 22.224, "unit": "kb", "free": 2420}, "slots": {}}}

Further testing

$ screen /dev/cu.usbmodem3468355632311 115200
# Press CTRL+A SHIFT+H to start screen log recording as `screenlog.0`
# Send {"m": "METHOD_NAME", "p": {}, "i": "1234"}
# Press CTRL+A SHIFT+H to stop screen log recording