gistfile1.c

#include <LiquidCrystal.h>

HardwareSPI spiSA9904(2);

const unsigned long LIMIT = 0xFFFFFF;   		//upperlimit for 24 bits  


int CountSamples = 0;
const int nSamples = 1;
bool sample = false;

float U = 0.0f;
float f = 0.0f;

unsigned long iLCDLoop = millis(); 

LiquidCrystal lcd(23, 24, 25, 26, 27, 28); 

void setup()
{
//Serial2.begin(115200);
  lcd.begin(20, 4);

  pinMode(BOARD_SPI2_NSS_PIN, OUTPUT);
  digitalWrite(BOARD_SPI2_NSS_PIN, LOW); 

  const int interruptPinSA9904B = 35;
  pinMode(interruptPinSA9904B, INPUT_FLOATING);
  attachInterrupt(interruptPinSA9904B, _F50sampleSA9904, FALLING);
}

void loop()
{
  if(sample) //read all registers starting from active 
  {
    F50sampleSA9904();
     ZobrazDataLCD();
 
    sample = false;
  }
}

void ZobrazDataLCD()
{
  if( millis() > iLCDLoop + 800 )
  {
        lcd.setCursor(0, 0); 
    lcd.print(millis()/1000, DEC);
    lcd.setCursor(0, 2); 
    lcd.print(U,3);
    lcd.setCursor(0, 3); 
    lcd.print(f,3);
//Serial2.println(U,3);
//Serial2.println(f,3);
    iLCDLoop = millis();
  }
}

void _F50sampleSA9904() // F50 impulse
{
  CountSamples++;
  if(CountSamples == nSamples)
  {
    sample = true;
    CountSamples = 0;
  }
}

void F50sampleSA9904()
{
  byte rx[36] = {};
  unsigned long reg1[4] = {};

  readSA9904B(0, rx, 36);

  reg1[2] = convertbutolong(rx, 6);
  reg1[3] = convertbutolong(rx, 9);

  U = float(reg1[2]);
  f = float(reg1[3]);
}

void readSA9904B(byte startreg, byte *data, byte bytesreq)
{
  spiSA9904.begin(SPI_281_250KHZ, MSBFIRST, SPI_MODE_0); 
  digitalWrite(BOARD_SPI2_NSS_PIN, HIGH);
  spiSA9904.transfer(0x01);
  spiSA9904.transfer(startreg | 0x80);
  spiSA9904.begin(SPI_281_250KHZ, MSBFIRST, SPI_MODE_1); 
  for(byte i = 0; i < bytesreq; i++)
    data[i]=spiSA9904.transfer(0x00);
  digitalWrite(BOARD_SPI2_NSS_PIN, LOW);
  spiSA9904.end();
}

unsigned long convertbutolong(byte *buf, int idx)
{
  return ((unsigned long)buf[idx]<<16 | (unsigned long)buf[idx+1]<<8 | (unsigned long)buf[idx+2])  & LIMIT;
}