Interfacing US 100 Distance with STM32 Blue Pill

US 100 practical reference

A drop-in HC-SR04 upgrade that adds temperature compensation and an optional UART mode for more consistent readings. The US-100 uses the same physical dual-transducer layout as the classic HC-SR04, so it fits existing mounts and wiring, but internally it corrects for the fact that the speed of sound changes with air temperature — giving noticeably steadier distance readings across hot and cold environments — and it can optionally be switched into a simple 3-wire UART mode that skips the fussy pulse-timing of the standard trigger/echo interface entirely.

Key specifications

• Sensor type: Dual-transducer ultrasonic ranging module with onboard temperature compensation
• Operating voltage: 2.4V–5.5V DC
• Operating current: ~2.2 mA
• Measuring range: 2cm to 450cm
• Accuracy: ±1% typical, improved over standard HC-SR04 thanks to temperature compensation
• Interface modes: Trigger/Echo pulse mode (pin-compatible with HC-SR04) or UART serial mode, selectable by a jumper
• UART settings: 9600 baud, 8N1, when jumper-configured for serial mode
• Temperature sensor: Onboard temperature sensor used internally to correct the speed-of-sound calculation

Pinout and connection notes

A small onboard jumper (often a solder pad or physical switch) selects between classic trigger/echo pulse mode — wired and coded exactly like an HC-SR04 — and UART serial mode, which instead streams distance readings as simple serial bytes at 9600 baud, avoiding the need for precise pulse-width timing in your microcontroller code.

• VCC: Power, 2.4–5.5V DC
• Trig / TX: Trigger input in pulse mode, or UART TX in serial mode (set by onboard jumper)
• Echo / RX: Echo output in pulse mode, or UART RX in serial mode
• GND: Ground

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.