update README with usage

README.md

@@ -8,8 +8,33 @@ This repository reproduces the C++ implementation of the [DFRobot Gravity TDS](h
 micropython -m mip install github:WendelHime/micropython-dftds
 ```
 
+If you're installing through thonny or developing something with another IDE, the package is also available on pypi:
+```bash
+pip install micropython-dftds
+```
+
 ## Testing
 
 ```bash
 micropython -m unittest tests/*
 ```
+
+## Usage
+
+```python
+from machine import ADC
+
+import dftds
+
+# must be an analog pin
+TDS_PIN = 28
+# create TDS object remembering to set the values according to your device. On raspberry pico the ADC range is 65535.
+# another thing to observe, on rasberry pico we have memory flash available, if you need this code to work on another storage device such as EEPROM you might need to create another implementation of KValueRepository. Feel free to open an PR and contribute.
+tds_sensor = dftds.GravityTDS(TDS_PIN, adc_range=65535, k_value_repository=dftds.KValueRepositoryFlash('tds_calibration.json'))
+tds_sensor.begin()
+
+# you can read the temperature using a dht22 or other device
+tds_sensor.temperature = 25.0
+tds_value = tds_sensor.update()
+print("TDS: {}ppm, EC: {} mS/cm".format(tds_value, tds_value*2))
+```