docs: Expand README for hts221 driver. (#220)

* docs: Expand README for hts221 driver.

* docs: Rewrite hts221 README addressing all review comments.

---------

Co-authored-by: Sébastien NEDJAR <sebastien@nedjar.com>

Author: Charly-sketch

lib/hts221/README.md

@@ -1,9 +1,139 @@
-# MicroPython Driver for the HTS221 Humidity Sensor
+# HTS221 MicroPython Driver
 
-This library is a port of the [MicroPython Driver for the HTS221 Humidity Sensor](https://github.com/jposada202020/MicroPython_HTS221/tree/master).
+MicroPython driver for the **STMicroelectronics HTS221** humidity and temperature sensor.
 
-The examples could be easily tested with [mpremote](https://docs.micropython.org/en/latest/reference/mpremote.html) with the following command :
+This library is a port of [MicroPython_HTS221](https://github.com/jposada202020/MicroPython_HTS221).
 
-```sh
- mpremote mount . run examples/humidity.py
+## Supported Sensor
+
+| Parameter            | Value             |
+| -------------------- | ----------------- |
+| Interface            | I²C               |
+| Default I²C address  | `0x5F`            |
+| Device ID            | `0xBC`            |
+| Humidity range       | 0–100 %RH         |
+| Humidity accuracy    | ±3.5 %RH          |
+| Temperature range    | −40 to +120 °C    |
+| Temperature accuracy | ±0.5 °C           |
+
+## Features
+
+* I²C communication
+* Device identification (`WHO_AM_I`)
+* Humidity and temperature measurement
+* One-shot and continuous measurement modes
+* Configurable output data rate (ODR)
+* Configurable averaging
+* Data-ready status flags
+* Power management (on/off, reboot)
+* Factory calibration (automatic)
+* User temperature calibration (offset and two-point)
+
+## Basic Usage
+
+```python
+from machine import I2C
+from hts221 import HTS221
+
+i2c = I2C(1)
+sensor = HTS221(i2c)
+
+humidity = sensor.humidity()
+temperature = sensor.temperature()
+
+print("Humidity:", humidity, "%")
+print("Temperature:", temperature, "°C")
+
+# Read both at once
+h, t = sensor.read()
+```
+
+## API Reference
+
+### Initialization
+
+```python
+sensor = HTS221(i2c, address=0x5F)
+```
+
+### Device Information
+
+```python
+sensor.device_id()
 ```
+
+Returns the sensor device ID (`WHO_AM_I` register, expected `0xBC`).
+
+### Measurements
+
+* `sensor.temperature()` — temperature in °C
+* `sensor.humidity()` — relative humidity in %
+* `sensor.read()` — returns `(humidity, temperature)`
+* `sensor.read_one_shot()` — triggers a one-shot conversion and returns `(humidity, temperature)` after a fixed 15 ms delay
+
+### Data Readiness
+
+* `sensor.data_ready()` — `True` when both humidity and temperature are available
+* `sensor.temperature_ready()` — `True` when temperature is available
+* `sensor.humidity_ready()` — `True` when humidity is available
+
+### One-Shot Mode
+
+```python
+sensor.trigger_one_shot()
+```
+
+Triggers a single conversion with a 15 ms delay. Used internally by `read_one_shot()`.
+
+### Configuration
+
+* `sensor.get_odr()` — returns current output data rate
+* `sensor.set_odr(odr)` — set ODR (0 = one-shot, 1 = 1 Hz, 2 = 7 Hz, 3 = 12.5 Hz)
+* `sensor.set_continuous(odr)` — enable continuous mode. Raises `ValueError` if `odr=0`.
+
+### Averaging
+
+* `sensor.get_av()` — returns current averaging configuration register
+* `sensor.set_av(av)` — set humidity and temperature averaging (raw register value)
+
+The AV_CONF register controls internal averaging for both channels. Higher values improve noise but increase conversion time. Refer to the HTS221 datasheet for the register encoding.
+
+### Power Management
+
+* `sensor.power_on()` — enable sensor
+* `sensor.power_off()` — disable sensor
+* `sensor.reboot()` — reload factory calibration data from non-volatile memory
+
+### Temperature Calibration
+
+```python
+# Simple offset correction
+sensor.set_temp_offset(-1.2)
+
+# Two-point calibration (gain + offset)
+sensor.calibrate_temperature(
+    ref_low=0.0,
+    measured_low=0.8,
+    ref_high=50.0,
+    measured_high=48.7,
+)
+```
+
+No calibration is required for basic usage — the driver applies factory calibration automatically.
+
+## Examples
+
+| File          | Description                            |
+| ------------- | -------------------------------------- |
+| `humidity.py` | Basic humidity and temperature reading |
+
+```bash
+mpremote mount lib/hts221 run lib/hts221/examples/humidity.py
+```
+
+## Notes
+
+* The driver uses factory calibration data stored in the sensor, read automatically at initialization.
+* `temperature()`, `humidity()`, and `read()` poll the sensor's status bits via `_ensure_data()` to wait for fresh data before returning.
+* `read_one_shot()` triggers a conversion and waits a fixed 15 ms delay before reading registers (no status polling).
+* In power-down or one-shot mode, calling a measurement method automatically triggers a new conversion.