ATtiny85: protótipo de sensor sem fio

Geralmente, para passar de uma ideia para uma implementação, é necessário um protótipo do dispositivo, conveniente para verificar e depurar no local, o que é especialmente importante para um dispositivo móvel. A seguir, tentarei analisar em detalhes o processo de criação de um protótipo de um sensor sem fio baseado no ATtiny85.

— , , : , , . CR2032, , 2.7V ( TMP36), 200mAh.

ATtiny85 5 / RESET . :

• 3 — NRF24L01+, , 3- ;
• 1 — BPW17N;
• 2 — TMP36, , .

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RESET /

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Arduino ATTiny Fuse Reset with 12 Volt Charge Pump. , 12V (Charge Pump).

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KiCad GitHub, attwlight_sensor.pcb.

, YouTube KiCAD Quick-Start Tutorial.

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NRF24L01+

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, CE (chip enable) , CSN (chip select) , . , CSN , SCK (clock). SCK C2 CSN , SCK , CSN. MISO MOSI , .

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ATtiny85

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BPW17N

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• NRF24L01+;
• ;
• ;
• WDT (WatchDog Timer);
• Pin Change PCINT;
• .

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• TMRh20/RF24
• TMRh20/RF24Network

NRF24L01+, ATtiny85. libraries Arduino.

. GitHub attwlight_sensor, attwlight_rx .

void sleep() void loop() PCINIT3 WDT. .

, . ATtiny85 datasheet «23. Register Summary», .

#include <avr/wdt.h>
#include <avr/sleep.h>
#include <avr/interrupt.h>

#define WDTO_INFINITE 255
#define SLEEP_PERIOD WDTO_8S
#define SKIP_WDT_WAKEUPS 14 // x SLEEP_PERIOD + SLEEP_PERIOD (14 ~= 120 sec)

//  ()  PCINT,  ATtiny85   (B),     PCINT
ISR(PCINT0_vect)
{
  light_pcint = true;
}

//    WDT
ISR(WDT_vect)
{
  wakeup_counter++;
}

void sleep()
{
  GIMSK = _BV(PCIE); //  Pin Change 
  if (SLEEP_PERIOD == WDTO_INFINITE || payload.light != LIGHT_FUZZY)
    PCMSK |= _BV(LIGHT_PIN); // PCINT3;           
  ADCSRA &= ~_BV(ADEN); //  ADC;  

  if (SLEEP_PERIOD != WDTO_INFINITE) {
    wdt_enable(SLEEP_PERIOD); //  
    WDTCR |= _BV(WDIE); //    ;   ATtiny85
  }

  //    Power-down; MCUSR &= ~_BV(SM0); MCUSR |= _BV(SM1);
  set_sleep_mode(SLEEP_MODE_PWR_DOWN);
  sleep_enable(); //   ; MCUSR |= _BV(SE);
  sei(); //  

  sleep_cpu(); // 

  cli(); //  ;    PCINT3
  PCMSK &= ~_BV(LIGHT_PIN); // PCINT3; 
  sleep_disable(); //   ; MCUSR &= ~_BV(SE);
  ADCSRA |= _BV(ADEN); //  ADC
  sei(); //  ;     
}

« ». , , 20μA.

#define FUZZY_VOLTAGE 0.4 //      ,  

const unsigned int fuzzy_start = int(1024.0 * (1.0 - FUZZY_VOLTAGE) / 2.0);
const unsigned int fuzzy_stop = 1023 - fuzzy_start;

light_t readLightStatus(unsigned int ms)
{
  delay(ms); //     
  int input = analogRead(LIGHT_PIN); // ADC3

  //   
  if (input >= fuzzy_start && input <= fuzzy_stop)
    return LIGHT_FUZZY;
  if (input < fuzzy_start)
    return LIGHT_OFF;
  if (input > fuzzy_stop)
    return LIGHT_ON;

  // ;     
  return LIGHT_UNKNOWN;
}

AREF , , . , , . .

, Vbg (Bandgap reference voltage) 1.1V. Vbg 1.0-1.2V, 1125300.

long readVcc()
{
  //    Vcc    Vbg == 1.1V
  ADMUX = _BV(MUX3) | _BV(MUX2);
  delay(2); //   1ms  
  ADCSRA |= _BV(ADSC); // ADC Start conversion -  
  while (bit_is_set(ADCSRA, ADSC)); // ADSC == 1   

  //  ADCL  ADCH,  ADCH    => ADCL  
  uint8_t low  = ADCL; //    ADC
  uint8_t high = ADCH; //    ADC

  long result = (high << 8) | low;

  result = 1125300L / result; // 1125300 = 1.1*1023*1000
  return result; // Vcc  
}

, .

float readTmp36(long vcc)
{
  int input = analogRead(TMP36_PIN); //   refVolts
  float refVolts = float(vcc) / 1000.0;
  float voltage = float(input) * refVolts / 1024.0; //  
  float temperatureC = (voltage - 0.5) * 100.0; //  500mV & 10mV == 1°C
  return temperatureC;
}

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, , 8KiB :

Sketch uses 7,120 bytes (86%) of program storage space. Maximum is 8,192 bytes.
Global variables use 227 bytes (44%) of dynamic memory, leaving 285 bytes for local variables. Maximum is 512 bytes.

, , Fuses RESET /. Arduino IDE , :

avrdude -c stk500v1 -p attiny85 -P /dev/ttyUSB0 -v -C /etc/avrdude.conf -b 19200 -U lfuse:w:0x62:m -U hfuse:w:0x5f:m -U efuse:w:0xff:m

• avrdude — Arduino IDE hardware/tools/avr/bin/;
• /dev/ttyUSB0 — ;
• /etc/avrdude.conf — Arduino IDE hardware/tools/avr/etc/avrdude.conf.

Fuses, Engbedded Atmel AVR® Fuse Calculator.

, : 8 ( 1MHz); , ; BOD (Brown-out Detector) — ; ; RESET.

. : 120sec, , ; ; 200mAh.

, . , 8MHz . , .

GitHub