lf-tds-ec

A reusable, self-contained TDS (Total Dissolved Solids) and EC (Electrical Conductivity) sensor driver library for the Raspberry Pi Pico / Pico 2 (RP2040 and RP2350 microcontrollers) using the Pico C SDK.

Features

• Averaged ADC Reads: Reads and averages 30 samples to filter out electrical noise from the analog breakout board.
• Third-Order Polynomial Conversion: Maps the non-linear relationship of voltage to raw Electrical Conductivity (\mu\text{S/cm}).
• Temperature Compensation (2% per °C): Adjusts conductivity readings according to temperature relative to a standard 25^\circ\text{C} baseline.
• Persistent Calibration (Flash-Based): Automatically loads and saves the probe's calibration factor (K) to the final 4KB sector of the Pico's external QSPI flash, keeping it safe across reboots.

Pinout & Connections

Make sure to power the transmitter board with 3.3\text{V} (Pico's 3V3 OUT pin), so the analog output does not exceed the Pico's ADC range.

TDS Breakout Pin	Pico GPIO Pin	Description
+	3V3 OUT	3.3V Power input
-	GND	Power Ground (0V)
A	GP26 (ADC0)	Analog output representing EC (Default in example)

Standalone Compilation

To compile the standalone example project:

mkdir build
cd build
cmake -DPICO_PLATFORM=rp2350 -DPICO_BOARD=pico2 ..
make

Flash the generated tds_ec_example.uf2 binary to your Pico 2.

Integrating as a Submodule / Subdirectory

You can drop this repository into your project directory (e.g. under drivers/lf-tds-ec) and add it to your root CMakeLists.txt:

add_subdirectory(drivers/lf-tds-ec)

target_link_libraries(my_project_name
    lf_tds_ec
)

This registers the static library target lf_tds_ec and handles header include paths automatically.