Full Arduino Mini LoraWAN below 1uA Sleep Mode

End Devices (Nodes)
32

@lex_ph2lb
Thanks for the pictures, very nice,

Yeah for AA clip I saw that and immediately fixed it in V1.1. But I didn’t shared the board before testing. I should receive new version soon (they have been shipped). V1.1 also add SCL/SDA other pinout so you can plug other type of Arduino Mini Clones, button has also been moved :wink:

But if you want to try before here is the link of V1.1 and even more exactly the same board with Grove connector instead

You can avoid RGB led and use the Mini on board led if you need :wink: Avoid blink while talking with RFM since onboard led is connected to a SPI pin as far as I remember. You can also solder a 3mm classic LED and I think it’s even possible to solder 0805 RGB between 2 pins of the RGB LED.

For voltage divider (I don’t like them because of consomption and I don’t have place to control voltage measurement with controlled FET to reduce consomption).
But, I have a trick for you, you can measure VCC (voltage applied on VCC pin of ATMega) from software, that’s what I do with my ULPNode Library (you may need to adapt code) but it works like a charm, I’m doing 8 samples and Using ADC in Low Power Mode to avoid noise.

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


volatile uint8_t  _adc_irq_cnt;

/* ======================================================================
Function: ADC_vect
Purpose : IRQ Handler for ADC 
Input   : - 
Output  : - 
Comments: used for measuring 8 samples low power mode, ADC is then in 
          free running mode for 8 samples
====================================================================== */
ISR(ADC_vect)  
{
  // Increment ADC counter
  _adc_irq_cnt++;
}


/* ======================================================================
Function: readADCLowNoise
Purpose : Read Analog Value with reducing noise
Input   : true return the average value, false return only the sum
Output  : average value read
Comments: hard coded to read 8 samples each time
          AD MUX Channel and ADC must have been set before this call
====================================================================== */
uint16_t readADCLowNoise(boolean average)
{
  uint8_t low, high;
  uint16_t sum = 0;
  
  // Start 1st Conversion, but ignore it, can be hazardous
  ADCSRA |= _BV(ADSC); 
  
  // wait for first dummy conversion
  while (bit_is_set(ADCSRA,ADSC));

  // Init our measure counter
  _adc_irq_cnt = 0;

  // We want to have a interrupt when the conversion is done
  ADCSRA |= _BV( ADIE );

  // Loop thru samples
  // 8 samples (we don't take the 1st one)
  do {
    // Enable Noise Reduction Sleep Mode
    set_sleep_mode( SLEEP_MODE_ADC );
    sleep_enable();

    // Wait until conversion is finished 
    do {
      // enabled IRQ before sleeping
      sei();
      sleep_cpu();
      cli();
    }
    // Check is done with interrupts disabled to avoid a race condition
    while (bit_is_set(ADCSRA,ADSC));

    // No more sleeping
    sleep_disable();
    sei();
    
    // read low first
    low  = ADCL;
    high = ADCH;
    
    // Sum the total
    sum += ((high << 8) | low);
  }
  while (_adc_irq_cnt<8);
  
  // No more interrupts needed for this
  // we finished the job
  ADCSRA &= ~ _BV( ADIE );
  
  // Return the average divided by 8 (8 samples)
  return ( average ? sum >> 3 : sum );
}

/* ======================================================================
Function: readVcc
Purpose : Read and Calculate V powered, the Voltage on Arduino VCC pin
Input   : -
Output  : value readed
Comments: ADC Channel input is modified
====================================================================== */
uint16_t readVcc() 
{
  uint16_t value; 

  // Enable ADC (just in case going out of low power)
  power_adc_enable();
  ADCSRA |= _BV(ADEN)  ;

  // Read 1.1V reference against AVcc
  // REFS1 REFS0          --> 0 1, AVcc internal ref. -Selects AVcc external reference
  // MUX3 MUX2 MUX1 MUX0  --> 1110 1.1V (VBG)         -Selects channel 14, bandgap voltage, to measure
  ADMUX = (0<<REFS1) | (1<<REFS0) | (0<<ADLAR) | (1<<MUX3) | (1<<MUX2) | (1<<MUX1) | (0<<MUX0);

  // Take care, changing reference from VCC to 1.1V bandgap can take some time, this is due
  // to the fact that the capacitor on aref pin need to discharge
  // or to charge when we're just leaving power down mode
  // power down does not hurt and 15ms strong enough for ADC setup
  delay(15);  

  // read value
  value = readADCLowNoise(true);

  // Vcc reference in millivolts
  _vcc =  ( 1023L * 1100L /*config.aRef*/) / value ; 
  
  // Operating range of ATMega
  if (_vcc < 1800 ) _vcc = 1800 ;
  if (_vcc > 5500 ) _vcc = 5500 ;
    
  // Vcc in millivolts
  return ( _vcc ); 
}

Yeah will put this on github as soon as I have a descent readme to push with it :wink:

5 Likes