Track magnet's rotational angle with AS5147U and ATmega324P
Contactless rotary positioning
Published Mar 09, 2023
Click board™
Magnetic Rotary 3 Click
Dev. board
EasyAVR v7
Compiler
NECTO Studio
MCU
ATmega324P
Accurate angular measurement over a full mechanical turn of 360°
A
A
Hardware Overview
How does it work?
Magnetic Rotary 3 Click is based on the AS5147U, a high-resolution rotary position sensor for fast absolute angle measurement over a full 360-degree range from ams AG. The AS5147U continuously generates the angle information, which the different interfaces can request from the device. The internal 14-bit resolution is available by readout register via the SPI interface, while the resolution on the ABI output can be programmed for 10 or 14 bits. It is also equipped with a Dynamic Angle Error Compensation block that corrects the calculated angle regarding latency by using a linear prediction calculation algorithm. The core of the AS5147U represents a CMOS technology Hall-effect magnetic sensor that converts the magnetic field component perpendicular to the surface of the chip into a voltage. The signals from internal Hall sensors are amplified and filtered before their conversion by the ADC and then processed by the CORDIC block
to compute the angle and magnitude of the magnetic field vector. The intensity of the magnetic field is used by the automatic gain control (AGC) to adjust the amplification level to compensate for temperature and magnetic field variations. Magnetic Rotary 3 Click communicates with MCU through a standard SPI interface supporting the common SPI mode, SPI Mode 1, allowing a host MCU to read 14-bit absolute angle position data from the AS5147U. This Click board™ also comes with onboard headers reserved for incremental and commutation signals of their respective A/B/I and U/V/W signals alongside embedded self-diagnostics, including magnetic field strength too high, magnetic field strength too low or lost magnet, and other related diagnostic features. Incremental movements are indicated on ABI signals with a maximum resolution of 16384 steps / 4096 pulses per revolution. Besides, brushless DC (BLDC) motors are also controllable
through a standard UVW commutation interface with a programmable number of pole pairs from 1 to 7. At constant rotation speed, the latency time is internally compensated by the AS5147U, reducing the dynamic angle error at the SPI, ABI, and UVW outputs, while at higher speeds, the interpolator fills in the missing ABI pulses and generates the UVW signals with no loss of resolution. The AS5147U allows selection between a UVW output interface and a PWM-encoded interface on the W pin, which can be seen as an absolute angle position. This Click board™ can only be operated from a 3.3V logic voltage level. Therefore, the board must perform appropriate logic voltage conversion before using MCUs with different logic levels. However, the Click board™ comes equipped with a library containing functions and an example code that can be used as a reference for further development.
Features overview
Development board
EasyAVR v7 is the seventh generation of AVR development boards specially designed for the needs of rapid development of embedded applications. It supports a wide range of 16-bit AVR microcontrollers from Microchip and has a broad set of unique functions, such as a powerful onboard mikroProg programmer and In-Circuit debugger over USB. The development board is well organized and designed so that the end-user has all the necessary elements in one place, such as switches, buttons, indicators, connectors, and others. With four different connectors for each port, EasyAVR v7 allows you to connect accessory boards, sensors, and custom electronics more
efficiently than ever. Each part of the EasyAVR v7 development board contains the components necessary for the most efficient operation of the same board. An integrated mikroProg, a fast USB 2.0 programmer with mikroICD hardware In-Circuit Debugger, offers many valuable programming/debugging options and seamless integration with the Mikroe software environment. Besides it also includes a clean and regulated power supply block for the development board. It can use a wide range of external power sources, including an external 12V power supply, 7-12V AC or 9-15V DC via DC connector/screw terminals, and a power source via the USB Type-B (USB-B)
connector. Communication options such as USB-UART and RS-232 are also included, alongside the well-established mikroBUS™ standard, three display options (7-segment, graphical, and character-based LCD), and several different DIP sockets which cover a wide range of 16-bit AVR MCUs. EasyAVR v7 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
Architecture
AVR
MCU Memory (KB)
32
Silicon Vendor
Microchip
Pin count
40
RAM (Bytes)
2048
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 EasyAVR v7 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 Magnetic Rotary 3 Click driver.
Key functions:
magneticrotary3_write_registerThis function writes desired data to the selected register by using SPI serial interface.magneticrotary3_read_registerThis function reads data from the selected register by using SPI serial interface.magneticrotary3_get_angleThis function reads the absolute position raw data and converts it to degrees (Angle).
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 MagneticRotary3 Click example
*
* # Description
* This example demonstrates the use of Magnetic Rotary 3 Click board by reading and displaying
* the magnet's angular position in degrees.
*
* The demo application is composed of two sections :
*
* ## Application Init
* Initializes the driver and logger.
*
* ## Application Task
* Reads the magnet's angular position in degrees every 100ms and displays the results on the USB UART.
*
* @author Stefan Filipovic
*
*/
#include "board.h"
#include "log.h"
#include "magneticrotary3.h"
static magneticrotary3_t magneticrotary3;
static log_t logger;
void application_init ( void )
{
log_cfg_t log_cfg; /**< Logger config object. */
magneticrotary3_cfg_t magneticrotary3_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.
magneticrotary3_cfg_setup( &magneticrotary3_cfg );
MAGNETICROTARY3_MAP_MIKROBUS( magneticrotary3_cfg, MIKROBUS_1 );
if ( SPI_MASTER_ERROR == magneticrotary3_init( &magneticrotary3, &magneticrotary3_cfg ) )
{
log_error( &logger, " Communication init." );
for ( ; ; );
}
log_info( &logger, " Application Task " );
}
void application_task ( void )
{
float angle;
if ( MAGNETICROTARY3_OK == magneticrotary3_get_angle ( &magneticrotary3, &angle ) )
{
log_printf( &logger, " Angle: %.1f degrees\r\n\n", angle );
Delay_ms ( 100 );
}
}
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
