Interfacing HX711 + Load Cell Weight / Load Cell with STM32 Blue Pill

HX711 + Load Cell practical reference

The HX711 is a 24-bit precision analog-to-digital converter (ADC) chip designed specifically for weigh-scale and industrial control applications. It amplifies and digitizes the tiny differential voltage produced by a load cell's Wheatstone bridge, turning raw strain-gauge signals into a clean digital reading a microcontroller can use. Paired with a bar-type or button load cell, it's the standard combo for building a DIY digital kitchen scale, a bench scale, or a weight-triggered trigger for automation projects.

Key specifications

• ADC resolution: 24-bit
• Operating voltage: 2.6V–5.5V (module regulator allows 5V logic and supply)
• Operating current: ~1.5 mA active, <1 µA in power-down
• Sample rate: 10 SPS or 80 SPS, selectable via the RATE pin
• Input channels: Channel A (gain 128 or 64), Channel B (gain 32)
• Interface: Simple 2-wire synchronous serial (DT/SCK, bit-banged — no dedicated hardware peripheral needed)
• Load cell type: Any 4-wire Wheatstone-bridge load cell (bar, S-type, button, or half-bridge pair)
• Typical load cell range: 1 kg, 5 kg, 10 kg, 20 kg, or 50 kg bar cells are the most common hobbyist sizes

Pinout and connection notes

Most breakout boards label the load cell terminal block as E+/E-/A+/A- and expect the standard 4-wire color code (red=E+, black=E-, white=A+, green=A-); some load cells swap green/white, so if readings are unstable or negative, try swapping A+ and A-. Channel B (B+/B-) is present on the HX711 IC itself but is rarely broken out on cheap modules.

• VCC: Power, 2.6–5.5V DC
• GND: Ground
• DT: Data output — serial data line, read by the microcontroller
• SCK: Serial clock input — clocks out each data bit and also selects gain/channel via pulse count
• E+: Load cell excitation positive — wire to the load cell's red wire
• E-: Load cell excitation negative — wire to the load cell's black wire
• A+: Channel A positive input — wire to the load cell's white wire
• A-: Channel A negative input — wire to the load cell's green wire

Integration checklist

1. Confirm the exact part number and breakout-board revision.
2. Verify supply voltage, current demand, logic levels, and signal direction against the datasheet.
3. Check controller pin assignments and bus address or interface mode against the example code.
4. Power up with external loads disconnected, then test signals before full integration.
5. If readings or communication fail, check power and ground first, then pin mapping, interface settings, and library initialization.

Troubleshooting and reproducibility

Record the board used, wiring, library/version, supply arrangement, and measured behavior. Use the selected board-specific wiring example as the source of truth. Never assume visually similar modules share identical voltage tolerance or pin order.