Design a receiver in a 4-20mA current loop standard with INA196 and ATmega328P
Receive and interpret the current signal
Published Feb 14, 2024
Click board™
4-20 mA R Click
Dev Board
Arduino UNO Rev3
Compiler
NECTO Studio
MCU
ATmega328P
Compact and efficient solution for receiving and monitoring current in industrial systems
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Hardware Overview
How does it work?
4-20mA R Click is based on the INA196, a current shunt monitor with a voltage output from Texas Instruments. The INA196 can sense drops across a shunt at a range of voltages without interference with its supply voltage and uses 500KHz bandwidth in current control loops. The 4-20mA R Click receives output current from 4 to 20mA from a compatible transmitter and converts it into low voltage. The transmitted loop current on this board comes directly to the load side of the INA196 shunt resistor from a VLOOP screw terminal. The
differential input voltage to the INA196 supply side comes from a TPS61041, a DC/DC boost converter from Texas Instruments. By default configuration, it provides a 16V and can be enabled over the EN pin of the mikroBUS™ socket. In addition, by replacing the R2 0ohm resistor with other values, it can also convert other voltages. The output of the INA196 then comes to the MCP3201, a 12-bit ADC from the Microchip. It communicates with the host microcontroller over an SPI serial interface of the mikroBUS™ socket, with the referent voltage of
2.048V. The ADC receives its reference from the MAX6106, a voltage reference LDO from Analog Devices. This Click board™ can operate either with 3.3V or 5V logic voltage levels selected via the PWR SEL jumper. This way, it is allowed for both 3.3V and 5V capable MCUs to use the communication lines properly. However, the Click board™ comes equipped with a library containing easy-to-use functions and an example code that can be used, as a reference, for further development.
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
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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
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 via Debug Mode
1. Once the code example is loaded, pressing the "DEBUG" button initiates the build process, programs it on the created setup, and enters Debug mode.
2. After the programming is completed, a header with buttons for various actions within the IDE becomes visible. Clicking the green "PLAY" button starts reading the results achieved with the Click board™. The achieved results are displayed in the Application Output tab.
Software Support
Library Description
This library contains API for 4-20mA R Click driver.
Key functions:
c420mar_read_data- This function reads the 16-bit current value from the SPI data register, and then normalizes and converts it to float
Open Source
Code example
This example can be found in NECTO Studio. Feel free to download the code, or you can copy the code below.
/*!
* \file
* \brief 420MaR Click example
*
* # Description
* This example showcases how to initialize, configure and use the 4-20 mA R click. It is a
* simple SPI communication module that acts as a receiver in a 4-20 current loop. The click
* reads current data and converts the analog signal to a digital 12-bit format.
*
* The demo application is composed of two sections :
*
* ## Application Init
* This function initializes and configures the logger and click modules.
*
* ## Application Task
* This function reads and displays current data every half a second.
*
* \author MikroE Team
*
*/
// ------------------------------------------------------------------- INCLUDES
#include "board.h"
#include "log.h"
#include "c420mar.h"
// ------------------------------------------------------------------ VARIABLES
static c420mar_t c420mar;
static log_t logger;
// ------------------------------------------------------ APPLICATION FUNCTIONS
void application_init ( )
{
log_cfg_t log_cfg;
c420mar_cfg_t cfg;
/**
* 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.
c420mar_cfg_setup( &cfg );
c420MAR_MAP_MIKROBUS( cfg, MIKROBUS_1 );
c420mar_init( &c420mar, &cfg );
}
void application_task ( )
{
float current;
current = c420mar_read_data( &c420mar );
log_printf( &logger, "-----------------------------\r\n" );
log_printf( &logger, " * Current: %.3f mA * \r\n", current );
Delay_ms( 500 );
}
void main ( )
{
application_init( );
for ( ; ; )
{
application_task( );
}
}
// ------------------------------------------------------------------------ END
