Source: reTerminal Built-In Devices

Note: raw/reTerminal built-in devices 1.md is identical to this file.

Programmable Interfaces via /sys/

All programmable data on Linux is exposed as files. reTerminal built-in devices use this principle.

3 Programmable LEDs

LED	Color
`usr_led0`	green
`usr_led1`	green
`usr_led2`	red or green (STA light)

Control path: /sys/class/leds/<led_name>/brightness

Brightness values: 0 = off, 255 = full brightness

Buzzer

Path: /sys/class/leds/usr_buzzer/brightness

Value: 0 = off, any non-zero = on

Luminosity Sensor

Path: /sys/bus/iio/devices/iio:device0/in_illuminance_input

cat /sys/bus/iio/devices/iio:device0/in_illuminance_input
# Output: 2719 (value in Lux)

Readable by all users (permissions: rw-r--r-- root root) — no sudo needed.

Permissions Problem (LEDs/Buzzer)

The /sys/class/leds/*/brightness files are root-owned, write-restricted:

-rw-r--r-- 1 root root 4096 Jan 26 brightness

These all FAIL:

echo 255 > /sys/class/leds/usr_led0/brightness     # Permission denied
sudo echo 255 > /sys/class/leds/usr_led0/brightness # Still denied! (> runs as user)

Why sudo echo > file fails: sudo applies to the echo command, not to the > redirect. The redirect runs as the current user, which lacks write permission.

Solution: sudo + tee

tee reads stdin and writes to both stdout AND files.

echo 255 | sudo tee /sys/class/leds/usr_led0/brightness   # LED on
echo 0   | sudo tee /sys/class/leds/usr_led0/brightness   # LED off
echo 1   | sudo tee /sys/class/leds/usr_buzzer/brightness  # Buzzer on
echo 0   | sudo tee /sys/class/leds/usr_buzzer/brightness  # Buzzer off

sudo applies to tee, which has root permission to write to the file.

seeed-python-rpi Python Library

Install

pip install git+https://github.com/Seeed-Studio/Seeed_Python_RPi/
pip install RPi-GPIO

Usage

import seeed_python_rpi.core as rt
import time
 
# Buzzer
rt.buzzer = True
time.sleep(1)
rt.buzzer = False
 
# LEDs (same pattern: rt.led0, rt.led1, etc.)

Running with root (required for hardware access)

# Method 1: command substitution (recommended)
sudo $(which python) buzz.py
 
# Method 2: elevate shell first
sudo -i
python buzz.py

The library is a wrapper around the /sys/ file operations.

Screen Orientation (kanshi + labwc)

To set landscape mode permanently:

Edit ~/.config/kanshi/config — change transform to 270
Edit ~/.config/labwc/rc.xml — add touch device mapping for seeed-tp

co-test

Explorer

reterminal-built-in-devices