Convert analog voltage into PWM signals with LTC6992CS6-1 and STM32F446RE
Generate PWM signals at frequencies up to 1 MHz, providing flexibility for high-speed applications
Published Mar 15, 2024
Click board™
AN to PWM 2 Click
Dev. board
UNI-DS v8
Compiler
NECTO Studio
MCU
STM32F446RE
Achieve precise analog-to-PWM signal conversion, enabling smooth control over devices like LEDs, heaters, and servo motors with minimal effort
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Hardware Overview
How does it work?
AN to PWM 2 Click is based on the LTC6992CS6, a voltage-controlled PWM generator from Analog Devices. This device is chosen because it keeps its output clocking at all times and offers glitch-free, a first cycle-accurate startup within 500μs of Power-On. The output of this Click board™ can source or sink up to 16 mA, and 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 a duty cycle linearly proportional to the input voltage. The output PWM signal is brought to the INT pin of the mikroBUS™ socket to enable fast and precise duty cycle measurement using the interrupt routines. The LTC6992CS6 has a MOD pin, which represents pulse-width modulation input where it is necessary to bring an analog signal. To bring the corresponding signal to that pin, this Click
board™ uses an analog circuitry made of OpAmp AD8616ARZ from Analog Devices. In the first part of the circuit, amplifier OPA1 adjusts the input signal through a reference voltage of 2.5V by the MCP1525 from Microchip and applies input voltage in a range of -2.5 to 2.5V. The next part of the circuit is the voltage divider and amplifier OPA2, which has the function of a buffer, after which the signal required by the MOD pin of the LTC6992CS6 is obtained. The output frequency can range up from 3.81Hz to 1MHz and is controlled via the AD5171, a 64-position (OTP) digital potentiometer from Analog Devices, which programs the LTC6992CS6’s internal master oscillator frequency. The output frequency is determined by this master oscillator and an internal frequency divider programmable to eight settings from 1 to 16384. It
communicates with MCU using the standard I2C serial interface that operates at clock rates up to 400 kHz and represents the most accurate way to set the frequency. It also left the possibility of adjusting the frequency via resistors RH and RL by placing appropriate resistors. This Click board™ is designed to be operated only with a 5V logic level. A proper logic voltage level conversion should be performed before the AN to PWM 2 Click is used with MCUs with different logic levels. More information about the LTC6992CS6’s functionality, electrical specifications, and typical performance can be found in the attached datasheet. However, the Click board™ comes equipped with a library that contains easy-to-use functions and a usage example that can be used as a reference for the development.
Features overview
Development board
UNI-DS v8 is a development board specially designed for the needs of rapid development of embedded applications. It supports a wide range of microcontrollers, such as different STM32, Kinetis, TIVA, CEC, MSP, PIC, dsPIC, PIC32, and AVR MCUs regardless of their number of pins, and a broad set of unique functions, such as the first-ever embedded debugger/programmer over WiFi. The development board is well organized and designed so that the end-user has all the necessary elements, such as switches, buttons, indicators, connectors, and others, in one place. Thanks to innovative manufacturing technology, UNI-DS v8 provides a fluid and immersive working experience, allowing access anywhere and under any
circumstances at any time. Each part of the UNI-DS v8 development board contains the components necessary for the most efficient operation of the same board. An advanced integrated CODEGRIP programmer/debugger module offers many valuable programming/debugging options, including support for JTAG, SWD, and SWO Trace (Single Wire Output)), and seamless integration with the Mikroe software environment. Besides, it also includes a clean and regulated power supply module for the development board. It can use a wide range of external power sources, including a battery, an external 12V power supply, and a power source via the USB Type-C (USB-C) connector. Communication options such as USB-UART, USB
HOST/DEVICE, CAN (on the MCU card, if supported), and Ethernet is also included. In addition, it also has the well-established mikroBUS™ standard, a standardized socket for the MCU card (SiBRAIN standard), and two display options for the TFT board line of products and character-based LCD. UNI-DS v8 is an integral part of the Mikroe ecosystem for rapid development. Natively supported by Mikroe software tools, it covers many aspects of prototyping and development thanks to a considerable number of different Click boards™ (over a thousand boards), the number of which is growing every day.
Microcontroller Overview
MCU Card / MCU
Type
8th Generation
Architecture
ARM Cortex-M4
MCU Memory (KB)
512
Silicon Vendor
STMicroelectronics
Pin count
64
RAM (Bytes)
131072
Used MCU Pins
mikroBUS™ mapper
Take a closer look
Click board™ Schematic
Step by step
Project assembly
Start by selecting your development board and Click board™. Begin with the UNI-DS v8 as your development board.
Track your results in real time
Application Output
1. Application Output - In Debug mode, the 'Application Output' window enables real-time data monitoring, offering direct insight into execution results. Ensure proper data display by configuring the environment correctly using the provided tutorial.
2. UART Terminal - Use the UART Terminal to monitor data transmission via a USB to UART converter, allowing direct communication between the Click board™ and your development system. Configure the baud rate and other serial settings according to your project's requirements to ensure proper functionality. For step-by-step setup instructions, refer to the provided tutorial.
3. Plot Output - The Plot feature offers a powerful way to visualize real-time sensor data, enabling trend analysis, debugging, and comparison of multiple data points. To set it up correctly, follow the provided tutorial, which includes a step-by-step example of using the Plot feature to display Click board™ readings. To use the Plot feature in your code, use the function: plot(*insert_graph_name*, variable_name);. This is a general format, and it is up to the user to replace 'insert_graph_name' with the actual graph name and 'variable_name' with the parameter to be displayed.
Software Support
Library Description
This library contains API for AN to PWM 2 Click driver.
Key functions:
antopwm2_set_frequency- This function sets a frequency output in a range from 500kHz to 1MHz by setting the digipot resistanceantopwm2_set_frequency_otp- This function sets a frequency output in a range from 500kHz to 1MHz by setting the digipot resistance in OTP mode
Open Source
Code example
The complete application code and a ready-to-use project are available through the NECTO Studio Package Manager for direct installation in the NECTO Studio. The application code can also be found on the MIKROE GitHub account.
/*!
* @file main.c
* @brief AN to PWM 2 Click example
*
* # Description
* This example demonstrates the use of AN to PWM 2 Click board by changing the PWM output
* frequency from 500kHz to 1MHz in steps of 50kHz.
*
* The demo application is composed of two sections :
*
* ## Application Init
* Initializes the driver and logger.
*
* ## Application Task
* Changes the PWM output frequency every 5 seconds in steps of 50kHz going through the full range
* from 500kHz to 1MHz. The currently set frequency will be displayed on the USB UART.
*
* @note
* Applying a voltage of -2.5 to 2.5V on the input will generate the PWM pulse train
* with a duty cycle linearly proportional to the input voltage.
*
* @author Stefan Filipovic
*
*/
#include "board.h"
#include "log.h"
#include "antopwm2.h"
static antopwm2_t antopwm2;
static log_t logger;
void application_init ( void )
{
log_cfg_t log_cfg; /**< Logger config object. */
antopwm2_cfg_t antopwm2_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.
antopwm2_cfg_setup( &antopwm2_cfg );
ANTOPWM2_MAP_MIKROBUS( antopwm2_cfg, MIKROBUS_1 );
if ( I2C_MASTER_ERROR == antopwm2_init( &antopwm2, &antopwm2_cfg ) )
{
log_error( &logger, " Communication init." );
for ( ; ; );
}
log_info( &logger, " Application Task " );
}
void application_task ( void )
{
static uint32_t freq = ANTOPWM2_FREQ_MIN;
if ( ANTOPWM2_OK == antopwm2_set_frequency ( &antopwm2, freq ) )
{
log_printf ( &logger, " Frequency: %lu Hz\r\n\n", freq );
}
freq += 50000;
if ( freq > ANTOPWM2_FREQ_MAX )
{
freq = ANTOPWM2_FREQ_MIN;
}
Delay_ms ( 1000 );
Delay_ms ( 1000 );
Delay_ms ( 1000 );
Delay_ms ( 1000 );
Delay_ms ( 1000 );
}
int main ( void )
{
/* Do not remove this line or clock might not be set correctly. */
#ifdef PREINIT_SUPPORTED
preinit();
#endif
application_init( );
for ( ; ; )
{
application_task( );
}
return 0;
}
// ------------------------------------------------------------------------ END
