ATtiny1614 Frequency Meter

/**
 * AUDIO FREQUENCY METER V4
 * Based on code from David Johnson-Davies - www.technoblogy.com - 16th March 2021
 * 2021-03-21 John Bradnam (jbrad2089@gmail.com)
 *    - Limited maximum frequency to 99999Hz (Design is primarily for audio frequencies)
 *    - Replaced OLED screen with 5 digit 7-Segment display
 * 
 * ATTiny1614 Pins mapped to Ardunio Pins
 *
 *             +--------+
 *         VCC + 1   14 + GND
 * (SS)  0 PA4 + 2   13 + PA3 10 (SCK)
 *       1 PA5 + 3   12 + PA2 9  (MISO)
 * (DAC) 2 PA6 + 4   11 + PA1 8  (MOSI)
 *       3 PA7 + 5   10 + PA0 11 (UPDI)
 * (RXD) 4 PB3 + 6    9 + PB0 7  (SCL)
 * (TXD) 5 PB2 + 7    8 + PB1 6  (SDA)
 *             +--------+
 *             
 * BOARD: ATtiny1614/1604/814/804/414/404/214/204
 * Chip: ATtiny1614
 * Clock Speed: 20MHz
 * millis()/micros(): "TCA0 (default on 0-series)"
 * Programmer: jtag2updi (megaTinyCore)
*/

//#include <avr/io.h>
//#include <avr/interrupt.h>
#include "LedControl.h"

#define MAX7219_DATA 0 //PA4
#define MAX7219_CLK 1 //PA5
#define MAX7219_LOAD 2 //PA6

#define FREQ_IN 8 //PA1
// PA2 is connected to PA3
// 32.768kHz crystal connected to TOSC1/PB3 and TOSC2/PB2

#define MAX7219_BRIGHTNESS 4
#define MAX7219_TOTAL_DIGITS 5

//LED order 7,3,2,4,6
int8_t digits[] = {6, 4, 2, 3, 7};

LedControl lc=LedControl(MAX7219_DATA,MAX7219_CLK,MAX7219_LOAD,1);

uint32_t overflowCounter;

//---------------------------------------------------------------------
//Set up frequency meter

void setup() 
{
  //The MAX72XX is in power-saving mode on startup, we have to do a wakeup call
  lc.shutdown(0,false);
  //Set the brightness to a medium values
  lc.setIntensity(0,MAX7219_BRIGHTNESS);
  //and clear the display
  lc.clearDisplay(0);

  TCDSetup();
  RTCSetup();
  EvsysSetup();
}

//---------------------------------------------------------------------
// Real-Time Clock Setup

volatile uint16_t MSByte;
volatile uint32_t Counter;

void RTCSetup () 
{
  uint8_t temp;
  // Initialize 32.768kHz Oscillator:

  // Disable oscillator:
  temp = CLKCTRL.XOSC32KCTRLA & ~CLKCTRL_ENABLE_bm;

  // Enable writing to protected register
  CPU_CCP = CCP_IOREG_gc;
  CLKCTRL.XOSC32KCTRLA = temp;

  while (CLKCTRL.MCLKSTATUS & CLKCTRL_XOSC32KS_bm); // Wait until XOSC32KS is 0
  
  temp = CLKCTRL.XOSC32KCTRLA & ~CLKCTRL_SEL_bm;    // Use External Crystal
  
  // Enable writing to protected register
  CPU_CCP = CCP_IOREG_gc;
  CLKCTRL.XOSC32KCTRLA = temp;
  
  temp = CLKCTRL.XOSC32KCTRLA | CLKCTRL_ENABLE_bm;  // Enable oscillator
  
  // Enable writing to protected register
  CPU_CCP = CCP_IOREG_gc;
  CLKCTRL.XOSC32KCTRLA = temp;
  
  // Initialize RTC
  while (RTC.STATUS > 0);                           // Wait until registers synchronized
  
  RTC.PER = 1023;                                   // Set period 1 second
  RTC.CLKSEL = RTC_CLKSEL_TOSC32K_gc;               // 32.768kHz External Crystal Oscillator  
  RTC.CTRLA = RTC_PRESCALER_DIV32_gc | RTC_RTCEN_bm;// Prescaler /32 and enable
}

//---------------------------------------------------------------------
// Timer/Counter TCD0 Setup

volatile boolean Ready = false;                     // New reading ready?

void TCDSetup () 
{ 
  TCD0.CTRLB = TCD_WGMODE_ONERAMP_gc;               // Set one ramp waveform mode
  TCD0.CMPBCLR = 0xFFF;                             // Count up to maximum
  TCD0.INPUTCTRLB = TCD_INPUTMODE_EDGETRIG_gc;      // Capture and reset counter
  TCD0.EVCTRLB = TCD_CFG_ASYNC_gc | TCD_ACTION_bm | TCD_TRIGEI_bm; // Enable event
  TCD0.INTCTRL = TCD_OVF_bm | TCD_TRIGB_bm;         // Enable interrupts

  // Ensure ENRDY bit is set
  while(!(TCD0.STATUS & TCD_ENRDY_bm));
  
  // External clock, no prescaler, enable timer
  TCD0.CTRLA = TCD_CLKSEL_EXTCLK_gc | TCD_CNTPRES_DIV1_gc | TCD_ENABLE_bm;
}

//---------------------------------------------------------------------
// Timer/Counter TCD0 overflow interrupt counts MSByte

ISR (TCD0_OVF_vect) 
{
  TCD0.INTFLAGS = TCD_OVF_bm;                       // Clear overflow interrupt flag
  MSByte++;
}

//---------------------------------------------------------------------
// Timer/Counter TCD0 capture interrupt

ISR (TCD0_TRIG_vect) 
{
  PORTA.IN = PIN4_bm;                               // Toggle LED on
  TCD0.INTFLAGS = TCD_TRIGB_bm;                     // Clear capture interrupt flag
  Counter = TCD0.CAPTUREB;
  Counter = (uint32_t)MSByte<<12 | Counter;
  MSByte = 0;
  Ready = true;
  PORTA.IN = PIN4_bm;                               // Toggle LED off
  TCD0.INTFLAGS = TCD_OVF_bm;                       // Clear overflow interrupt flag
}

//---------------------------------------------------------------------
// Event System Setup

void EvsysSetup (void) 
{
  EVSYS.ASYNCCH1 = EVSYS_ASYNCCH1_RTC_OVF_gc;       // Event generated from RTC OVF
  EVSYS.ASYNCUSER7 = EVSYS_ASYNCUSER7_ASYNCCH1_gc;  // Event causes a TCD0 capture
  
  EVSYS.ASYNCCH0 = EVSYS_ASYNCCH0_PORTA_PIN1_gc;    // PA1 is an event generator
  EVSYS.ASYNCUSER8 = EVSYS_ASYNCUSER8_ASYNCCH0_gc;  // ASYNCUSER8 is EVOUT0 (PA2)
  PORTMUX.CTRLA = PORTMUX_EVOUT0_bm;                // Enable EVOUT0
  PORTA.PIN1CTRL = PORT_INVEN_bm;                   // Invert input
}

//---------------------------------------------------------------------
// Main program loop

void loop() 
{ 
  uint32_t temp;
  unsigned long start = millis();
  while (!Ready) 
  {
    if (millis() - start > 1000) 
    {
      Counter = 0;
      break;
    }
  }
  Ready = false;
  
  cli(); 
  temp = Counter; 
  sei();
  writeNumber(temp);
}

//---------------------------------------------------------------------
// Display a number on the LED display
//   num - Number to display between 0 and 99999

void writeNumber(long num)
{
  if (num > 9999999)
  {
    //Display "Error"
    lc.setChar(0, digits[4], 'E', false);
    lc.setRow(0, digits[3], 0x05);
    lc.setRow(0, digits[2], 0x05);
    lc.setChar(0, digits[1], 'o', false);
    lc.setRow(0, digits[0], 0x05);
  }
  else
  {
    bool X1000 = false;
    if (num > 99999)
    {
      X1000 = true;
      num = (num + 500) / 1000;
    }
    for (int i = 0; i < MAX7219_TOTAL_DIGITS; i++)
    {
      if (X1000 && i == 0)
      {
        lc.setChar(0, digits[i], 'H', false);
      }
      else if (num > 0 || i == 0)
      {
        lc.setDigit(0, digits[i], num % 10, false);
        num = num / 10;
      }
      else
      {
        lc.setChar(0, digits[i], ' ', false);
        num = num / 10;
      }
    }
  }
}