/stm8-hc-sr04

Ultrasonic range meter on STM8+HC-SR04

Primary LanguageC

Ultrasonic range meter on STM8+HC-SR04

HC-SR04

  • Range: 2-400 cm
  • Trigger: 10+ us
  • Interval: 60+ ms
  • Range [cm] = X us / 58
  • Echo pulse length: 116-23200 us
  • Delay until echo: ~480 us

STM8

Clock

  • HSI = 16 MHz
  • HSI DIV = 8
  • MASTER CLK = 2 MHz
  • CPU DIV = 1
  • CPU CLK = 2 MHz

CCO

  • PC4 - CCO

UART

  • PD5 - TX
  • PD6 - RX

GPIO

  • PB5 - LED
  • PD2 - Trigger
  • PD3 - Echo (TIM2_CH2)

TIM2

Measures echo delay

  • TIM2 Prescaler = 2
  • TIM2 CLK = 1 MHz
  • TIM2 Tick = 1 us
  • TIM2 Max Interval = 65535 us = 65.5 ms

TIM4

Triggers measurement every ~ 1s