V to Hz 3 Click

V to Hz 3 Click is a compact add-on board that converts an analog voltage input signal into a specific frequency pulse wave signal. This board features the AD7740, an ultrasmall synchronous voltage-to-frequency converter from Analog Devices. The AD7740 has a linear response, so applying a voltage from 3V up to 5V on its VIN terminal will generate the pulse with a frequency linearly proportional to the input voltage. It contains an integrated 2.5V bandgap reference defining the span of the VFC and can be overdriven using an external reference. The full-scale output frequency is synchronous with the input clock signal provided by the LTC6903 programmable oscillator, with a maximum input frequency of 1MHz. Based on the analog input value, the output frequency goes from 10% to 90% of the input frequency.

Click Product page

Click library

• Author : Stefan Filipovic
• Date : Jul 2021.
• Type : SPI type

Software Support

We provide a library for the VtoHz3 Click as well as a demo application (example), developed using MikroElektronika compilers. The demo can run on all the main MikroElektronika development boards.

Package can be downloaded/installed directly from NECTO Studio Package Manager(recommended way), downloaded from our LibStock™ or found on Mikroe github account.

Library Description

This library contains API for VtoHz3 Click driver.

Standard key functions :

• vtohz3_cfg_setup Config Object Initialization function.

  void vtohz3_cfg_setup ( vtohz3_cfg_t *cfg );

• vtohz3_init Initialization function.

  err_t vtohz3_init ( vtohz3_t *ctx, vtohz3_cfg_t *cfg );

Example key functions :

• vtohz3_set_input_frequency This function enables and sets output frequency of the programmable oscillator, which is the AD7740 input frequency.

  err_t vtohz3_set_input_frequency ( vtohz3_t *ctx, uint32_t freq );

• vtohz3_read_an_pin_voltage This function reads results of AD conversion of the AN pin and converts them to proportional voltage level.

  err_t vtohz3_read_an_pin_voltage ( vtohz3_t *ctx, float *data_out );

• vtohz3_get_frequency This function converts voltage to the estimated output frequency in Hz.

  uint32_t vtohz3_get_frequency ( vtohz3_t *ctx, float voltage, float vref_in );

Example Description

This example demonstrates the use of the V to Hz 3 Click board by calculating the estimated output frequency from the input voltage.

The demo application is composed of two sections :

Application Init

Initializes the driver and sets the input frequency.

void application_init ( void )
{
    log_cfg_t log_cfg;        /**< Logger config object. */
    vtohz3_cfg_t vtohz3_cfg;  /**< Click config object. */

    /** 
     * Logger initialization.
     * Default baud rate: 115200
     * Default log level: LOG_LEVEL_DEBUG
     * @note If USB_UART_RX and USB_UART_TX 
     * are defined as HAL_PIN_NC, you will 
     * need to define them manually for log to work. 
     * See @b LOG_MAP_USB_UART macro definition for detailed explanation.
     */
    LOG_MAP_USB_UART( log_cfg );
    log_init( &logger, &log_cfg );
    log_info( &logger, " Application Init " );

    // Click initialization.
    vtohz3_cfg_setup( &vtohz3_cfg );
    VTOHZ3_MAP_MIKROBUS( vtohz3_cfg, MIKROBUS_1 );
    if ( SPI_MASTER_ERROR == vtohz3_init( &vtohz3, &vtohz3_cfg ) ) 
    {
        log_error( &logger, " Application Init Error. " );
        log_info( &logger, " Please, run program again... " );

        for ( ; ; );
    }

    vtohz3_set_input_frequency ( &vtohz3, VTOHZ3_DEFAULT_IN_FREQUENCY );
    log_info( &logger, " Application Task " );
}

Application Task

Reads the input voltage from AN pin and calculates the output frequency from it. The results are being displayed on the USB UART approximately once per second.

void application_task ( void )
{
    float voltage;
    if ( VTOHZ3_OK == vtohz3_read_an_pin_voltage ( &vtohz3, &voltage ) ) 
    {
        log_printf( &logger, " Voltage : %.2f V\r\n", voltage );
        log_printf( &logger, " Output frequency : %lu Hz\r\n\n", 
                    vtohz3_get_frequency ( &vtohz3, voltage, VTOHZ3_VREF_INTERNAL_2V5 ) );
    }
    Delay_ms ( 1000 );
}

The full application code, and ready to use projects can be installed directly from NECTO Studio Package Manager(recommended way), downloaded from our LibStock™ or found on Mikroe github account.

Other Mikroe Libraries used in the example:

• MikroSDK.Board
• MikroSDK.Log
• Click.VtoHz3

Additional notes and informations

Depending on the development board you are using, you may need USB UART Click, USB UART 2 Click or RS232 Click to connect to your PC, for development systems with no UART to USB interface available on the board. UART terminal is available in all MikroElektronika compilers.