ATtiny202で省電力なレインセンサーを作ってみた。

スイッチサイエンスで販売されている静電容量式のレインセンサー基板を使って省電力なレインセンサーを作ってみた。

以前に公開した光センサーのLEDの代わりにレインセンサー基板を接続しただけだ。

レインセンサーの静電容量(乾燥時約170pF程度)に充電した後に放電を開始し閾値(1.1V)まで電圧が下がるまでの時間を計測する。センサー表面が乾燥時より長い時間のパルスが出力されたら雨が降ってきたと判断することができる。出力は安定しているので誤検出の心配もなさそうだ。

ATtiny202のAC入力インピーダンスはかなり高そう(数十ＧΩ以上)なので数pF程度まで図れるかもしれない。

【回路】
※センサーとの配線距離は極力短くすること！！

【ファームウェア(Microchip Studio)】

/*
 main.cpp - Low Power LED Optical Sensor Firmware for Microchip AVR0/1 Series

 Copyright (c) 2023 Sasapea's Lab. All right reserved.

 This library is free software; you can redistribute it and/or
 modify it under the terms of the GNU Lesser General Public
 License as published by the Free Software Foundation; either
 version 2.1 of the License, or (at your option) any later version.

 This library is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 Lesser General Public License for more details.

 You should have received a copy of the GNU Lesser General
 Public License along with this library; if not, write to the
 Free Software Foundation, Inc., 59 Temple Place, Suite 330,
 Boston, MA  02111-1307  USA
 */

//#define F_CPU 20000000   // 20MHz    (OSC20M)
//#define F_CPU  1250000   // 1.25MHz  (OSC20M)
#define F_CPU    32768   // 32.786KHz (OSCULP32K)

#include <avr/io.h>
#include <avr/cpufunc.h>
#include <avr/interrupt.h>
#include <avr/sleep.h>
#include <util/delay.h>
#include <string.h>

#define INTERVAL_TIME    1000         // ms
#define AC_OUT_MIN_WIDTH 1000         // us

#if defined(__AVR_ATtiny202__)
  #define PIN_LED_CATHODE PIN7_bp     // PA7
  #define PIN_LED_ANODE   PIN6_bp     // PA6
  #define PIN_OUTPUT      PIN2_bp     // PA2
  #define PIN_AC_OUT      PIN3_bp     // PA3
  #define PIN_AC_OUT_CTRL PORTA.PIN3CTRL
#elif defined(__AVR_ATtiny1614__)
  #define PIN_LED_CATHODE PIN7_bp     // PA7
//  #define PIN_LED_ANODE   PIN6_bp     // PA6
  #define PIN_LED_ANODE   PIN4_bp     // PA4 (for test board)
  #define PIN_OUTPUT      PIN2_bp     // PA2
  #define PIN_AC_OUT      PIN5_bp     // PA5
  #define PIN_AC_OUT_CTRL PORTA.PIN5CTRL
#endif

#if !defined(AC_LPMODE_bm)
  #define AC_LPMODE_bm 0
#endif

#define ATOMIC(...) \
do { \
  uint8_t sreg_save = SREG; \
  cli(); \
  __VA_ARGS__; \
  SREG = sreg_save; \
} while (0)

#define SBI(port, bit) \
  do { \
    if (_SFR_IO_REG_P(port)) \
      asm volatile ("sbi %0, %1" :: "I" (_SFR_IO_ADDR(port)), "I" (bit)); \
    else \
      ATOMIC(port |= _BV(bit)); \
  } while (0)

#define CBI(port, bit) \
  do { \
    if (_SFR_IO_REG_P(port)) \
      asm volatile ("cbi %0, %1" :: "I" (_SFR_IO_ADDR(port)), "I" (bit)); \
    else \
      ATOMIC(port &= ~_BV(bit)); \
  } while (0)

ISR(RTC_CNT_vect)
{
  RTC.INTFLAGS = RTC_OVF_bm;
}

ISR(PORTA_PORT_vect)
{
  SBI(VPORTA_INTFLAGS, PIN_AC_OUT);
  // Output LOW
  CBI(VPORTA_OUT, PIN_OUTPUT);
}

void clock_select(void)
{
#if F_CPU == 32768
  _PROTECTED_WRITE(CLKCTRL_MCLKCTRLB, 0);
  _PROTECTED_WRITE(CLKCTRL_MCLKCTRLA, CLKCTRL_CLKSEL_OSCULP32K_gc);
#elif F_CPU == 1250000
  _PROTECTED_WRITE(CLKCTRL_MCLKCTRLB, CLKCTRL_PDIV_16X_gc | CLKCTRL_PEN_bm);
#elif F_CPU == 20000000
  _PROTECTED_WRITE(CLKCTRL_MCLKCTRLB, 0);
#endif
}

void disable_inputs(void)
{
#if defined(PORTA)
  memset((void *)&PORTA.PIN0CTRL, PORT_ISC_INPUT_DISABLE_gc, 8);
#endif
#if defined(PORTB)
  memset((void *)&PORTB.PIN0CTRL, PORT_ISC_INPUT_DISABLE_gc, 8);
#endif
#if defined(PORTC)
  memset((void *)&PORTC.PIN0CTRL, PORT_ISC_INPUT_DISABLE_gc, 8);
#endif
#if defined(PORTD)
  memset((void *)&PORTD.PIN0CTRL, PORT_ISC_INPUT_DISABLE_gc, 8);
#endif
}

int main(void)
{
  // Disable all GPIO inputs
  disable_inputs();

  // PORT Configuration
  SBI(VPORTA_OUT, PIN_LED_CATHODE);
  SBI(VPORTA_DIR, PIN_LED_ANODE);
  SBI(VPORTA_DIR, PIN_OUTPUT);

  // VREF Configuration
  VREF.CTRLA = VREF_DAC0REFSEL_1V1_gc;

  // AC0 Configuration
  AC0.MUXCTRLA = AC_MUXPOS_PIN0_gc | AC_MUXNEG_VREF_gc;
  AC0.CTRLA    = AC_RUNSTDBY_bm | AC_OUTEN_bm | AC_LPMODE_bm | AC_HYSMODE_OFF_gc | AC_ENABLE_bm;

  // RTC Configuration
  while (RTC.STATUS)
    continue;
  RTC.PER     = (INTERVAL_TIME * 32768UL / 1000) - 1;
  RTC.INTCTRL = RTC_OVF_bm;
  RTC.CLKSEL  = RTC_CLKSEL_INT32K_gc;
  RTC.CTRLA   = RTC_RUNSTDBY_bm | RTC_PRESCALER_DIV1_gc | RTC_RTCEN_bm;

  // Sleep Mode Configuration
  set_sleep_mode(SLEEP_MODE_STANDBY);
  sleep_enable();

  // Clock Select
  clock_select();

  // Main Loop
  while (1)
  {
    sei();
    // Minimum LOW Pulse Width
    _delay_us(AC_OUT_MIN_WIDTH);
    // Interval Sleep
    sleep_cpu();
    // Output HIGH
    SBI(VPORTA_OUT, PIN_OUTPUT);
    // Charge to LED Parasitic Capacitance
    SBI(VPORTA_DIR, PIN_LED_CATHODE);
    // Minimum HIGH Pulse Width
    _delay_us(AC_OUT_MIN_WIDTH);
    // AC_OUT Pin Interrupt Enable
    PIN_AC_OUT_CTRL = PORT_ISC_BOTHEDGES_gc;
    cli();
    // Discharge from LED Parasitic Capacitance
    CBI(VPORTA_DIR, PIN_LED_CATHODE);
    // Wait AC_OUT Pin Interrupt
    do
    {
      sei();
      sleep_cpu();
      cli();
    }
    while (VPORTA_OUT & _BV(PIN_OUTPUT));
    // AC_OUT Pin Interrupt Disable
    PIN_AC_OUT_CTRL = PORT_ISC_INTDISABLE_gc;
    SBI(VPORTA_INTFLAGS, PIN_AC_OUT);
  }
}

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main.cpp - Low Power LED Optical Sensor Firmware for Microchip AVR0/1 Series

This library is free software; you can redistribute it and/or

modify it under the terms of the GNU Lesser General Public

License as published by the Free Software Foundation; either

version 2.1 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful,

but WITHOUT ANY WARRANTY; without even the implied warranty of

MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU

Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General

Public License along with this library; if not, write to the

Free Software Foundation, Inc., 59 Temple Place, Suite 330,

Boston, MA 02111-1307 USA

//#define F_CPU 20000000 // 20MHz (OSC20M)

//#define F_CPU 1250000 // 1.25MHz (OSC20M)

#define F_CPU 32768 // 32.786KHz (OSCULP32K)

#include <avr/io.h>

#include <avr/cpufunc.h>

#include <avr/interrupt.h>

#include <avr/sleep.h>

#include <util/delay.h>

#include <string.h>

#define INTERVAL_TIME 1000 // ms

#define AC_OUT_MIN_WIDTH 1000 // us

#if defined(__AVR_ATtiny202__)

#define PIN_LED_CATHODE PIN7_bp // PA7

#define PIN_LED_ANODE PIN6_bp // PA6

#define PIN_OUTPUT PIN2_bp // PA2

#define PIN_AC_OUT PIN3_bp // PA3

#define PIN_AC_OUT_CTRL PORTA.PIN3CTRL

#elif defined(__AVR_ATtiny1614__)

#define PIN_LED_CATHODE PIN7_bp // PA7

// #define PIN_LED_ANODE PIN6_bp // PA6

#define PIN_LED_ANODE PIN4_bp // PA4 (for test board)

#define PIN_OUTPUT PIN2_bp // PA2

#define PIN_AC_OUT PIN5_bp // PA5

#define PIN_AC_OUT_CTRL PORTA.PIN5CTRL

#endif

#if !defined(AC_LPMODE_bm)

#define AC_LPMODE_bm 0

#endif

#define ATOMIC(...) \

do { \

uint8_t sreg_save = SREG; \

cli(); \

__VA_ARGS__; \

SREG = sreg_save; \

} while (0)

#define SBI(port, bit) \

do { \

if (_SFR_IO_REG_P(port)) \

asm volatile ("sbi %0, %1" :: "I" (_SFR_IO_ADDR(port)), "I" (bit)); \

else \

ATOMIC(port |= _BV(bit)); \

} while (0)

#define CBI(port, bit) \

do { \

if (_SFR_IO_REG_P(port)) \

asm volatile ("cbi %0, %1" :: "I" (_SFR_IO_ADDR(port)), "I" (bit)); \

else \

ATOMIC(port &= ~_BV(bit)); \

} while (0)

ISR(RTC_CNT_vect)

{

RTC.INTFLAGS = RTC_OVF_bm;

}

ISR(PORTA_PORT_vect)

{

SBI(VPORTA_INTFLAGS, PIN_AC_OUT);

// Output LOW

CBI(VPORTA_OUT, PIN_OUTPUT);

}

void clock_select(void)

{

#if F_CPU == 32768

_PROTECTED_WRITE(CLKCTRL_MCLKCTRLB, 0);

_PROTECTED_WRITE(CLKCTRL_MCLKCTRLA, CLKCTRL_CLKSEL_OSCULP32K_gc);

#elif F_CPU == 1250000

_PROTECTED_WRITE(CLKCTRL_MCLKCTRLB, CLKCTRL_PDIV_16X_gc | CLKCTRL_PEN_bm);

#elif F_CPU == 20000000

_PROTECTED_WRITE(CLKCTRL_MCLKCTRLB, 0);

#endif

}

void disable_inputs(void)

{

#if defined(PORTA)

memset((void *)&PORTA.PIN0CTRL, PORT_ISC_INPUT_DISABLE_gc, 8);

#endif

#if defined(PORTB)

memset((void *)&PORTB.PIN0CTRL, PORT_ISC_INPUT_DISABLE_gc, 8);

#endif

#if defined(PORTC)

memset((void *)&PORTC.PIN0CTRL, PORT_ISC_INPUT_DISABLE_gc, 8);

#endif

#if defined(PORTD)

memset((void *)&PORTD.PIN0CTRL, PORT_ISC_INPUT_DISABLE_gc, 8);

#endif

}

int main(void)

{

// Disable all GPIO inputs

disable_inputs();

// PORT Configuration

SBI(VPORTA_OUT, PIN_LED_CATHODE);

SBI(VPORTA_DIR, PIN_LED_ANODE);

SBI(VPORTA_DIR, PIN_OUTPUT);

// VREF Configuration

VREF.CTRLA = VREF_DAC0REFSEL_1V1_gc;

// AC0 Configuration

AC0.MUXCTRLA = AC_MUXPOS_PIN0_gc | AC_MUXNEG_VREF_gc;

AC0.CTRLA = AC_RUNSTDBY_bm | AC_OUTEN_bm | AC_LPMODE_bm | AC_HYSMODE_OFF_gc | AC_ENABLE_bm;

// RTC Configuration

while (RTC.STATUS)

continue;

RTC.PER = (INTERVAL_TIME * 32768UL / 1000) - 1;

RTC.INTCTRL = RTC_OVF_bm;

RTC.CLKSEL = RTC_CLKSEL_INT32K_gc;

RTC.CTRLA = RTC_RUNSTDBY_bm | RTC_PRESCALER_DIV1_gc | RTC_RTCEN_bm;

// Sleep Mode Configuration

set_sleep_mode(SLEEP_MODE_STANDBY);

sleep_enable();

// Clock Select

clock_select();

// Main Loop

while (1)

{

sei();

// Minimum LOW Pulse Width

_delay_us(AC_OUT_MIN_WIDTH);

// Interval Sleep

sleep_cpu();

// Output HIGH

SBI(VPORTA_OUT, PIN_OUTPUT);

// Charge to LED Parasitic Capacitance

SBI(VPORTA_DIR, PIN_LED_CATHODE);

// Minimum HIGH Pulse Width

_delay_us(AC_OUT_MIN_WIDTH);

// AC_OUT Pin Interrupt Enable

PIN_AC_OUT_CTRL = PORT_ISC_BOTHEDGES_gc;

cli();

// Discharge from LED Parasitic Capacitance

CBI(VPORTA_DIR, PIN_LED_CATHODE);

// Wait AC_OUT Pin Interrupt

{

sei();

sleep_cpu();

cli();

}

while (VPORTA_OUT & _BV(PIN_OUTPUT));

// AC_OUT Pin Interrupt Disable

PIN_AC_OUT_CTRL = PORT_ISC_INTDISABLE_gc;

SBI(VPORTA_INTFLAGS, PIN_AC_OUT);

}

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