add README

.gitignore

@@ -3,3 +3,4 @@
 .vscode/c_cpp_properties.json
 .vscode/launch.json
 .vscode/ipch
+/.vscode/settings.json

README.md

+# PH-260BD
+
+## Description
+This PlatformIO project allows you to get the pH, EC and temperature values from the cheap online water quality monitor PH-260BD
+
+## Usage
+Open this project in PlatformIO and write it to an ESP32. No further hardware or wiring needed.
+You'll get the values from the PH-260BD, which it sends every second, written to the serial monitor every 5 seconds.
+
+## Hints
+* The EC values are calculated based on the currently selected display unit, because that's what the PH-260BD sends.
+* The PH-260BD uses the factor `700` for `mS` <-> `ppm` calculation, which seems to be the standard in the Australian (and most likely Asian) part of the world.
+* You can change that factor at the top of the code to `500` (US) or `640` (EU), but that will of course only affect the calculated values, not the display on the PH-260BD.
+* The most accurate units to chose on the display for the calculation are probably `uS` and `ppm`.
+* The calculated values are properly rounded as expected.
+* The temperature value is truncated when the device is set to display `ppt`, which is why it's ignored from that data packet (but taken from `pH`).
+
+## Credits
+*  [Bo Jeanes](https://bjeanes.com/), for his [ESPHome implementation](https://gist.github.com/bjeanes/4310d30393a093bc2f1f2bd113fa820bm) of this (which i read less than i really should have)
\ No newline at end of file

src/main.cpp

@@ -44,7 +44,7 @@ void bleDataCallback(const char *match,
   }
   else if (unit == "uS")
   {
-    sensorData->put("ec_ms", value.toFloat() / 1000);
+    sensorData->put("ec_ms", (double) value.toFloat() / 1000);
     sensorData->put("ec_us", value.toFloat());
     sensorData->put("ec_ppm", value.toFloat() / 1000 * factorMsToPpm);
     sensorData->put("ec_ppt", value.toFloat() / 1000 * factorMsToPpm / 1000);