mirror of
https://github.com/jbranchaud/til
synced 2026-07-05 17:00:17 +00:00
jbranchaud
90 lines
3.0 KiB
Markdown
90 lines
3.0 KiB
Markdown
# Read The Lid Angle Sensor For A MacBook
|
||
|
||
MacOS has a bunch of internal HID (Human Interface Device) data that can surface
|
||
details about all kinds of "devices" that comprise your machine. Some obvious
|
||
ones are the keyboard and trackpad as well as external mice and keyboards. The
|
||
battery and power source details are another which is sometimes integrated into
|
||
tools that display battery status (e.g.
|
||
[`tmux-battery`](https://github.com/tmux-plugins/tmux-battery)), though it uses
|
||
`pmset` directly). And many, many more.
|
||
|
||
One example I'd never considered is that there is a sensor for the lid angle of
|
||
the laptop that can tell the system whether the lid is open or closed and how
|
||
open it is (i.e. at what angle). There is no public interface for this lid angle
|
||
sensor, but people exploring all the HID devices have found the identifiers that
|
||
correspond to it (e.g.
|
||
[`pybooklid`](https://github.com/tcsenpai/pybooklid/blob/main/pybooklid/macbook_lid.py)).
|
||
|
||
Here is a minimal script that uses `uv`, `hidapi` (python bindings), and
|
||
`libhidapi` (shared runtime lib for those bindings):
|
||
|
||
```python
|
||
#!/usr/bin/env -S uv run --quiet --script
|
||
# /// script
|
||
# requires-python = ">=3.10"
|
||
# dependencies = ["hidapi"]
|
||
# ///
|
||
"""Print MacBook lid angle in degrees."""
|
||
import os, sys
|
||
|
||
if sys.platform == "darwin":
|
||
brew = "/opt/homebrew/lib"
|
||
if os.path.exists(brew):
|
||
os.environ["DYLD_LIBRARY_PATH"] = f"{brew}:{os.environ.get('DYLD_LIBRARY_PATH','')}"
|
||
|
||
import hid
|
||
|
||
VENDOR_ID, PRODUCT_ID = 0x05AC, 0x8104
|
||
USAGE_PAGE, USAGE = 0x0020, 0x008A
|
||
REPORT_ID = 1
|
||
|
||
def read_angle():
|
||
for info in hid.enumerate(VENDOR_ID, PRODUCT_ID):
|
||
if info.get("usage_page") == USAGE_PAGE and info.get("usage") == USAGE:
|
||
d = hid.device()
|
||
path = info["path"]
|
||
d.open_path(path if isinstance(path, bytes) else path.encode())
|
||
try:
|
||
data = d.get_feature_report(REPORT_ID, 8)
|
||
if data and len(data) >= 3:
|
||
return float((data[2] << 8) | data[1])
|
||
finally:
|
||
d.close()
|
||
return None
|
||
|
||
if __name__ == "__main__":
|
||
a = read_angle()
|
||
if a is None:
|
||
sys.exit("sensor not available")
|
||
print(f"{a:.0f}")
|
||
```
|
||
|
||
These IDs and usage values are the undocumented values that allow the script to
|
||
navigate specifically to the lid angle sensor and specifically to the usage page
|
||
and value that represent the current lid angle reading.
|
||
|
||
```
|
||
VENDOR_ID, PRODUCT_ID = 0x05AC, 0x8104
|
||
USAGE_PAGE, USAGE = 0x0020, 0x008A
|
||
REPORT_ID = 1
|
||
```
|
||
|
||
I added [this
|
||
script](https://github.com/jbranchaud/dotfiles/blob/cbc7196607d1d6b25885f5387ca85b658bd765de/bin/lidangle)
|
||
to [my dotfiles](https://github.com/jbranchaud/dotfiles) and made it executable
|
||
(`chmod +x bin/lidangle`) so that I can try it out. I first ran it while it was
|
||
closed and connected to my external monitor (`0`), then I opened it as far as it
|
||
could go (`129`), and then I tried angling it close to what I thought was 90
|
||
degress (`92`, so close).
|
||
|
||
```bash
|
||
❯ lidangle
|
||
0
|
||
|
||
❯ lidangle
|
||
129
|
||
|
||
❯ lidangle
|
||
92
|
||
```
|