File content as of revision 9:0b84a8ce225a:

/*
 * mbed Application program / Frequency Counter
 *
 * Copyright (c) 2014,'15,'20 Kenji Arai / JH1PJL
 *  http://www7b.biglobe.ne.jp/~kenjia/
 *  https://os.mbed.com/users/kenjiArai/
 *      Created: October   18th, 2014
 *      Revised: August     4th, 2020
 */

//#define USE_TEXT_LCD    // use Text LCD/I2C Interface

#include "mbed.h"
#include "freq_counter.h"

#define GATE_TIME_10SEC     10000000
#define GATE_TIME_1SEC      1000000
#define GATE_TIME_100MS     100000
#define GATE_TIME_10MS      10000

#define GATE_TIME   GATE_TIME_1SEC

extern void print_revision(void);

// LPC1768 ---------------------------------------------------------------------
#if defined(TARGET_LPC1768)

// LPC1768 Frequency example
// Ref Clock output -> "PWM6" pin to 96MHZ/19 = 5.052MHz (Approx)
#   define CLK_REFRENCE()  PWM6_SETCLK(19)
// Outout mbed's "PWM6" pin to 96MHZ/96 = 1.000MHz (Approx)
//#define CLK_REFRENCE()    PWM6_SETCLK(96)

DigitalOut led_gate(LED1);
I2C i2cBus(p9, p10);    // SDA, SCL
PwmOut fmclck(p21);     // for RESERVE pin21 as PWM1[6]
F_COUNTER fc(p30);

void PWM6_SETCLK(int div);


// LPC1114 ---------------------------------------------------------------------
#elif defined(TARGET_LPC1114)

// LPC1114 Frequency example
// Ref Clock output -> "dp24" pin as CLOCKOUT

DigitalOut led_gate(LED2);
I2C i2cBus(dp5,dp27);   // SDA, SCL
F_COUNTER fc(dp14);

void clock_out(void);
#   define CLK_REFRENCE()  clock_out()
#   warning "Don't forget LPC1114 runs with internal clock."
#   warning "Measurement data is not accurate!!"

// STM32 / Nucleo --------------------------------------------------------------
#elif defined(TARGET_NUCLEO_F401RE)\
    || defined(TARGET_NUCLEO_F411RE)\
    || defined(TARGET_NUCLEO_F446RE)

// STM32 Frequency example
// Ref Clock output -> "PC_9" pin as MCO2 System clock / 4

DigitalOut led_gate(LED1);
I2C i2cBus(PB_9,PB_8);  // SDA, SCL
F_COUNTER fc(PA_0);

void port_mco2_set(void);
#   define CLK_REFRENCE()  port_mco2_set()

// Other CPU's -----------------------------------------------------------------
#else
#   error "No support for your CPU"
#endif

//  Only for LCD control -------------------------------------------------------
#if defined(USE_TEXT_LCD)
#include "TextLCD.h"    // Std. lib./ LCD control
// LCD(Akizuki AQM0802A)
TextLCD_I2C_N lcd(&i2cBus, 0x7c, TextLCD::LCD8x2);
void lcd_onotialize(void);
void display_on_lcd(float freqency, uint32_t t_gate);
#   define LCD_INITIALIZE()     lcd_onotialize()
#   define DISPLAY_ON_LCD(x,y)  display_on_lcd(x,y)
#else
#   define LCD_INITIALIZE()     {;}
#   define DISPLAY_ON_LCD(x,y)  {;}
#endif

//------------------------------------------------------------------------------
//  Control Program
//------------------------------------------------------------------------------
int main()
{
    float freqency;
    uint32_t t_gate;

    print_revision();
    printf("\r\nFrequency Counter by JH1PJL created on " __DATE__ "\r\n");
    // lcd
    LCD_INITIALIZE();
    // Set Internalclock for reference
    CLK_REFRENCE();
    while(true) {
        led_gate = 1;
        t_gate = GATE_TIME;
        freqency = (float)fc.read_frequency(t_gate);
        led_gate = 0;
        printf("f= %9.0f [Hz], gate= %4.3f [Sec]\r\n",
               freqency, (float)t_gate / 1e6);
        DISPLAY_ON_LCD(freqency, t_gate);
    }
}

#if defined(TARGET_LPC1768)

// Clock Output From pin21(PWM6)
// Set Clock Freq with div.
// if mbed is running at 96MHz, div is set 96 to Get 1MHz.
void PWM6_SETCLK(int div)
{
    // 1)Reset counter, disable PWM
    LPC_PWM1->TCR = (1 << 1);
    LPC_SC->PCLKSEL0 &= ~(0x3 << 12);
    // 2)Set peripheral clock divider to /1, i.e. system clock
    LPC_SC->PCLKSEL0 |= (1 << 12);
    // 3)Match Register 0 is shared period counter for all PWM1
    LPC_PWM1->MR0 = div - 1;
    LPC_PWM1->MR6 = (div + 1)>> 1;
    // 4)Start updating at next period start
    LPC_PWM1->LER |= 1;
    // 5)Enable counter and PWM
    LPC_PWM1->TCR = (1 << 0) + (1 << 3);
    printf("Set pin21(PWM6) for clock output\r\n");
}

#elif defined(TARGET_LPC1114)

// CLOCKOUT from pin24(dp18)
//      Freq = 48MHz/4 = 12MHz
void clock_out(void)
{
    LPC_SYSCON->CLKOUTCLKSEL = 3;       // System clock
    LPC_SYSCON->CLKOUTDIV = 4;          // div 1/4
    LPC_IOCON->PIO0_1 = 1;              // select CLKOUT to P0_1(pin24)/dp18
    LPC_SYSCON->CLKOUTUEN = 1;          // enable output
    printf("Set P0_1(pin24)/dp18 for clock output\r\n");
}

#elif defined(TARGET_NUCLEO_F401RE)\
    || defined(TARGET_NUCLEO_F411RE)\
    || defined(TARGET_NUCLEO_F446RE)

void port_mco2_set(void)
{
    // PC9 -> MCO_2
    DigitalOut dumy1(PC_9);
    uint32_t temp =
        ((uint32_t)(GPIO_AF0_MCO) << (((uint32_t)9 & (uint32_t)0x07) * 4)) ;
    GPIOC->AFR[9 >> 3] &=
        ~((uint32_t)0xf << ((uint32_t)(9 & (uint32_t)0x07) * 4)) ;
    GPIOC->AFR[9 >> 3] |= temp;
    GPIOC->MODER &= ~(GPIO_MODER_MODER0 << (9 * 2));
    GPIOC->MODER |= (0x2 << (9 * 2));
    GPIOC->OSPEEDR |= (0x03 << (9 * 2)); // High speed
    // Select output clock source
    RCC->CFGR &= 0x009fffff;
    // MCO_2 output SYSCLK 1/4
    //             MCO2          MCO2PRE
    RCC->CFGR |= (0x0 << 30) + (0x6 << 27);
    printf("Set PC9 for clock output\r\n");
}

#else
#   error "No support for your CPU"
#endif

#if defined(USE_TEXT_LCD)
void lcd_onotialize(void)
{
    // Initialize LCD
    lcd.locate(0, 0);    // 1st line top
    //          12345678
    lcd.printf("Fre-Cntr");
    lcd.locate(0, 1);    // 2nd line top
    //        12345678
    lcd.puts(" JH1PJL ");
    lcd.setCursor(TextLCD::CurOff_BlkOff);
    lcd.setContrast(0x16);
    thread_sleep_for(5000);
    lcd.locate(0, 1);    // 2nd line top
    //        12345678
    lcd.puts("        ");
}

void display_on_lcd(float freqency, uint32_t t_gate)
{
    lcd.locate(0, 0);    // 1st line top
    lcd.printf("%8.0f", freqency);
    lcd.locate(0, 1);    // 2nd line top
    switch (t_gate) {
        case GATE_TIME_10SEC:
            //          12345678
            lcd.printf("Hz  x0.1");
            break;
        case GATE_TIME_1SEC:
            //          12345678
            lcd.printf("Hz    x1");
            break;
        case GATE_TIME_100MS:
            //          12345678
            lcd.printf("Hz   x10");
            break;
        case GATE_TIME_10MS:
            //          12345678
            lcd.printf("Hz  x100");
            break;
        default:
            //          12345678
            lcd.printf("Hz gate?");
            break;
    }
}
#endif