Master electrical power analysis with MCP3910 and ATmega328P
Voltage, current, and beyond
Published Feb 14, 2024
Click board™
PWR Meter 2 click
Dev. board
Arduino UNO Rev3
Compiler
NECTO Studio
MCU
ATmega328P
Our groundbreaking power monitoring solution is designed to provide unrivaled accuracy in measuring and monitoring voltage and current values, ensuring optimal performance and efficiency in your electrical systems.
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Hardware Overview
How does it work?
PWR Meter 2 Click is based on the MCP3910, an integrated two-channel analog front-end (AFE) device from Microchip. This IC is composed of several sections, aimed at accurate capturing of the input voltage. Two sigma-delta input A/D converters used with the internal reference voltage of 1.2V with very low thermal drift, reducing the measurement noise at a minimum, yielding Signal to Noise ratio (SNR) up to 96dB. The input ADCs are fully configurable and can be set to work in 16-bit or 24-bit mode, can use oversampling ratio from 32 X up to 4096 X, gain ratio from 1 X to 32 X, and 24-bit digital offset and gain error correction for each ADC channel. The Click board™ is clocked by a 20MHz crystal. However, it is up to the user to set the pre-scalers correctly, according to the datasheet of the MCP3910. However, the included library offers functions which take care about correct settings. High clock speed allows maximum oversampling rate (OSR) to be used, allowing the best performance to be achieved, but consuming more power at the same time. The voltage and current readings are performed over two differential ADC input channels of the MCP3910 itself. The CH0 (Channel 0) is connected to a resistor voltage
divider, allowing it to measure up to 0.6V when the input voltage is 24V, which is the maximum voltage at the input terminal. Although the voltage across a differential input on the ADC channel can go up to ±2V, it is recommended by the manufacturer to stay within the ±0.6V margin to achieve optimal harmonic distortion and noise ratios, which might affect the measurement accuracy. The CH1 (Channel 1) differential input is connected to the shunt resistor of 0.03 Ω. A small voltage drop is measured by the ADC, allowing up to 5A of current to be measured. More of 5A might destroy the shunt resistor so it is not recommended going over 5A. The current measurement is done by connecting the load in series with the Click board™, so the shunt value of 0.03Ω will not introduce significant error or influence the current through the load. The measurement is performed using so-called Kelvin connections, where the main trace carries the majority of the current, while thin traces are used to measure the voltage across the shunt, reducing the current running through the ADC section of the IC itself. Additional 270 Ω resistors reduce the current through the ADC even further. The MCP3910 contains several additional pins, which
are used to simplify the implementation and reduce the bulkiness of the firmware application. The Data Ready pin can be used to trigger an interrupt event on the host MCU when there is conversion data ready to be read. This simplifies the MCU performance greatly, saving it from having to poll status bits in order to determine if the data is ready for reading. The Data Ready pin is routed to the mikroBUS™ INT pin, labeled as the DR. Two Modulator Output pins are also routed to the mikroBUS™. These pins offer direct 1-bit data output directly from the delta-sigma modulators for a user-defined MCU or DSP filtering, overriding the internal SINC filter, which is turned off if these pins are activated. The DR pin is also disabled when these pins are enabled. MDAT0 and MDAT1 pins offer modulator output from ADC channel 0 and ADC channel 1. These pins are routed to mikroBUS™ pins PWM and AN and are labeled as MDT0 and MDT1, respectively. As already mentioned, the Click board™ offers measurement of either internal power supply from the mikroBUS™, or the externally with up to 24V and 5A. To select the measurement target, the SMD jumper labeled INPUT SEL should be switched to the desired position.
Features overview
Development board
Arduino UNO is a versatile microcontroller board built around the ATmega328P chip. It offers extensive connectivity options for various projects, featuring 14 digital input/output pins, six of which are PWM-capable, along with six analog inputs. Its core components include a 16MHz ceramic resonator, a USB connection, a power jack, an
ICSP header, and a reset button, providing everything necessary to power and program the board. The Uno is ready to go, whether connected to a computer via USB or powered by an AC-to-DC adapter or battery. As the first USB Arduino board, it serves as the benchmark for the Arduino platform, with "Uno" symbolizing its status as the
first in a series. This name choice, meaning "one" in Italian, commemorates the launch of Arduino Software (IDE) 1.0. Initially introduced alongside version 1.0 of the Arduino Software (IDE), the Uno has since become the foundational model for subsequent Arduino releases, embodying the platform's evolution.
Microcontroller Overview
MCU Card / MCU
Architecture
AVR
MCU Memory (KB)
32
Silicon Vendor
Microchip
Pin count
28
RAM (Bytes)
2048
You complete me!
Accessories
Click Shield for Arduino UNO has two proprietary mikroBUS™ sockets, allowing all the Click board™ devices to be interfaced with the Arduino UNO board without effort. The Arduino Uno, a microcontroller board based on the ATmega328P, provides an affordable and flexible way for users to try out new concepts and build prototypes with the ATmega328P microcontroller from various combinations of performance, power consumption, and features. The Arduino Uno has 14 digital input/output pins (of which six can be used as PWM outputs), six analog inputs, a 16 MHz ceramic resonator (CSTCE16M0V53-R0), a USB connection, a power jack, an ICSP header, and reset button. Most of the ATmega328P microcontroller pins are brought to the IO pins on the left and right edge of the board, which are then connected to two existing mikroBUS™ sockets. This Click Shield also has several switches that perform functions such as selecting the logic levels of analog signals on mikroBUS™ sockets and selecting logic voltage levels of the mikroBUS™ sockets themselves. Besides, the user is offered the possibility of using any Click board™ with the help of existing bidirectional level-shifting voltage translators, regardless of whether the Click board™ operates at a 3.3V or 5V logic voltage level. Once you connect the Arduino UNO board with our Click Shield for Arduino UNO, you can access hundreds of Click boards™, working with 3.3V or 5V logic voltage levels.
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 Arduino UNO Rev3 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 PWR Meter 2 Click driver.
Key functions:
pwrmeter2_get_data- This function gets the calculated voltage( V ), current( A ) and power( W ) datapwrmeter2_write_reg- This function writes 24-bit data to the registerpwrmeter2_read_reg- This function reads the desired number of 24-bit data from the register/registers.
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
* \brief PwrMeter2 Click example
*
* # Description
* This app measuring and monitoring voltage up to 24V and current up to 5A.
*
* The demo application is composed of two sections :
*
* ## Application Init
* Initializes device.
*
* ## Application Task
* Gets calculated voltage, current and power data every 500 milliseconds
* and shows results on UART.
*
* \author MikroE Team
*
*/
// ------------------------------------------------------------------- INCLUDES
#include "board.h"
#include "log.h"
#include "pwrmeter2.h"
// ------------------------------------------------------------------ VARIABLES
static pwrmeter2_t pwrmeter2;
static log_t logger;
// ------------------------------------------------------ APPLICATION FUNCTIONS
void application_init ( void )
{
log_cfg_t log_cfg; /**< Logger config object. */
pwrmeter2_cfg_t pwrmeter2_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.
pwrmeter2_cfg_setup( &pwrmeter2_cfg );
PWRMETER2_MAP_MIKROBUS( pwrmeter2_cfg, MIKROBUS_1 );
if ( SPI_MASTER_ERROR == pwrmeter2_init( &pwrmeter2, &pwrmeter2_cfg ) )
{
log_error( &logger, " Communication init." );
for ( ; ; );
}
if ( PWRMETER2_ERROR == pwrmeter2_default_cfg ( &pwrmeter2 ) )
{
log_error( &logger, " Default configuration." );
for ( ; ; );
}
log_info( &logger, " Application Task " );
}
void application_task ( void )
{
float voltage = 0;
float current = 0;
float power = 0;
if ( PWRMETER2_OK == pwrmeter2_get_data( &pwrmeter2, &voltage, ¤t, &power ) )
{
log_printf( &logger, " U = %.3f V\r\n", voltage );
log_printf( &logger, " I = %.3f A\r\n", current );
log_printf( &logger, " P = %.3f W\r\n\n", power );
Delay_ms ( 500 );
}
}
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
