AN To PWM Click

How does it work?

AN to PWM Click is a device that converts an analog voltage input signal into a pulse width modulated (PWM) output signal. This Click board™ consists of an analog circuitry, made of two comparators and two op-amps, needed for the described device. Op-amps used on this Click board™ are OPA365 series, while comparators used are TLV 3201, both from Texas Instruments. It has a linear response, so applying a voltage in a range of -2.5 to 2.5V on its input, will result in generating the PWM pulse train with duty cycle linearly proportional to the input voltage.

This circuit on this Click board™ utilizes a triangle wave generator and comparator to generate a pulse-width-modulated (PWM) waveform with a duty cycle that is inversely proportional to the input voltage. An op amp and comparator generate a triangular waveform which is passed to the inverting input of a second comparator. By passing the input voltage to the non-inverting comparator input, a PWM waveform is produced. Negative feedback of the PWM waveform to an error amplifier is utilized to ensure high accuracy and linearity of the output.

One op-amp (U1a) and one comparator (U3) are used in order to form the triangle wave generator. The error amplifier, composed of one op-amp U1b, serves two purposes. First, the error amplifier accommodates feedback of the output PWM waveform in order to correct for any errors in the output voltage introduced by the comparator on the output of the circuit (U2). Second, it adds a dc offset to the input voltage so that negative input voltages can be accommodated by the circuit. That way, in case that input signal is equal to 0V, the value of PWM duty cycle on the output is 50%.

The output PWM signal on the AN to PWM Click is brought to the INT pin of the mikroBUS™ socket, in order to enable fast and precise duty cycle measurement, using the interrupt routines. The frequency of the PWM signal is fixed to 500kHz.

This Click Board™ is designed to be operated only with 5V logic level. A proper logic voltage level conversion should be performed before the Click board™ is used with MCUs with logic levels of 3.3V.

Specifications

Pinout diagram

This table shows how the pinout on V to HZ click corresponds to the pinout on the mikroBUS™ socket (the latter shown in the two middle columns).

Notes	Pin					Pin	Notes
	NC	1	AN	PWM	16	NC
	NC	2	RST	INT	15	INT	PWM Output
	NC	3	CS	RX	14	NC
	NC	4	SCK	TX	13	NC
	NC	5	MISO	SCL	12	NC
	NC	6	MOSI	SDA	11	NC
	NC	7	3.3V	5V	10	5V	Power Suppluy
Ground	GND	8	GND	GND	9	GND	Ground

Onboard settings and indicators

Software Support

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

Library Description

The library contains a interrupt pin state function.

Key functions:

• uint8_t antopwm_get_int_state( ) – Gets interrupt pin state

Examples description

The application is composed of three sections :

• System Initialization – Initializes the INT pin required to measure.
• Application Initialization – Initializes the driver and timer on 1us
• Application Task – Waits for the + command entered. When a command is entered, it calculates the PWM signal and the voltage on the INT pin.

void application_task ( )
{
    uint8_t drdy;
    char rsp_data;

    drdy = UART_Rdy_Ptr( );

    if ( drdy != 0 )
    {
        rsp_data = UART_Rd_Ptr( );

        switch ( rsp_data )
        {
            case '+' :
            {
                // Reset flags
                period_flag = 0;
                idle_high_cnt = 0;
                idle_low_cnt = 0;
                period_cnt = 0;
                    
                while ( period_flag != 1 );
                
                idle_high_cnt /= 10;
                idle_low_cnt /= 10;

                if ( ( idle_high_cnt != 0 ) && ( idle_high_cnt != 0 ) )
                {
                    tmp_value = calc_percentage( idle_high_cnt );
                    FloatToStr( tmp_value, demo_text );
                    mikrobus_logWrite( "> Idle [HIGH]: ~ ", _LOG_TEXT );
                    mikrobus_logWrite( demo_text, _LOG_TEXT );
                    mikrobus_logWrite( " %", _LOG_LINE );

                    tmp_value = calc_percentage( idle_low_cnt );
                    FloatToStr( tmp_value, demo_text );
                    mikrobus_logWrite( "> Idle [LOW]: ~ ", _LOG_TEXT );
                    mikrobus_logWrite( demo_text, _LOG_TEXT );
                    mikrobus_logWrite( " %", _LOG_LINE );

                    tmp_value = calc_voltage( idle_high_cnt );
                    FloatToStr( tmp_value , demo_text );
                    mikrobus_logWrite( "> Voltage: ~ ", _LOG_TEXT );
                    mikrobus_logWrite( demo_text, _LOG_TEXT );
                    mikrobus_logWrite( " mV", _LOG_LINE );

                    mikrobus_logWrite( "--------------------------------", _LOG_LINE );
                }
                mikrobus_logWrite( "--- Please, enter the command [ + ].", _LOG_LINE );
                break;
            }
        }
    }
}

Additional Functions :

• calc_percentage( ) – Represented data as a percentage
• calc_voltage( ) – Voltage calculation
• timer_init_1us( ) – Sets timer on 1us

The full application code, and ready to use projects can be found on our LibStock page.

Other mikroE Libraries used in the example:

• Conversions
• UART library

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. The terminal available in all MikroElektronika compilers, or any other terminal application of your choice, can be used to read the message.

mikroSDK

This Click board™ is supported with mikroSDK – MikroElektronika Software Development Kit. To ensure proper operation of mikroSDK compliant Click board™ demo applications, mikroSDK should be downloaded from the LibStock and installed for the compiler you are using.

For more information about mikroSDK, visit the official page.