Convert analog to digital signals with AD7091R and PIC18F25K80 with additional electrical isolation between them
Isolate and digitize with precision
Published Nov 01, 2023
Click board™
ISO ADC 2 Click
Dev. board
EasyPIC v8
Compiler
NECTO Studio
MCU
PIC18F25K80
Unleash the power of isolation with our cutting-edge A/D converter!
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Hardware Overview
How does it work?
ISO ADC 2 Click is based on the AD7091R, a 12-bit successive-approximation analog-to-digital converter (ADC) with an isolated DC-DC converter from Analog Devices. This Click board™ allows single-supply operation and consists of active Analog Devices components: AD8616, a level shifting circuit; AD7091R, an ADC stage; and ADuM5401, an output isolation stage. The AD8616 is chosen for this application because of its low offset voltage, low bias current, and low noise. The output of the OpAmp is 0.1V to 2.4V, which matches the input range of the ADC (0V to 2.5V) with a 100mV safety margin to maintain linearity. A single-pole RC filter (R2/C9) follows the OpAmp output stage to reduce the out-of-band noise. The next part of the circuit is the AD7091R, ADC chosen because of its
ultralow power, which is significantly lower than any competitive A/D converter. It features a power-down option, implemented across the serial interface to save power between conversions, described in the Modes of Operation section in the datasheet. After a successful conversion, the ADC sends the data to the MCU through galvanic isolation provided by the ADuM5401 quad-channel digital isolator with an integrated DC-DC converter. The isolator has a secondary side controller architecture with isolated pulse-width modulation (PWM) feedback, and it works on the principle common to most switching power supplies. The ISO ADC 2 Click communicates with MCU using the 3-wire SPI serial interface that operates at clock rates up to 50MHz used for accessing data from the result register
and controlling the device's modes of operation. The CONVST signal of the AD7091R routed to the RST pin on the mikroBUS™ is used to initiate the conversion process, data acquisition, and select the operation mode. This ADC requires the user to initiate a software reset upon Power-Up, and it should be noted that failure to apply the correct software reset command may result in a device malfunction. This Click board™ can operate with either 3.3V or 5V logic voltage levels selected via the VCC SEL jumper. This way, both 3.3V and 5V capable MCUs can 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
EasyPIC v8 is a development board specially designed for the needs of rapid development of embedded applications. It supports many high pin count 8-bit PIC microcontrollers from Microchip, regardless of their number of pins, and a broad set of unique functions, such as the first-ever embedded debugger/programmer. 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, EasyPIC v8 provides a fluid and immersive working experience, allowing access anywhere and under any
circumstances at any time. Each part of the EasyPIC v8 development board contains the components necessary for the most efficient operation of the same board. In addition to the advanced integrated CODEGRIP programmer/debugger module, which offers many valuable programming/debugging options and seamless integration with the Mikroe software environment, the board 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 DEVICE, and CAN are also included, including the well-established mikroBUS™ standard, two display options (graphical and character-based LCD), and several different DIP sockets. These sockets cover a wide range of 8-bit PIC MCUs, from the smallest PIC MCU devices with only eight up to forty pins. EasyPIC 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
Architecture
PIC
MCU Memory (KB)
32
Silicon Vendor
Microchip
Pin count
28
RAM (Bytes)
3648
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 EasyPIC v8 as your development board.
Software Support
Library Description
This library contains API for ISO ADC 2 Click driver.
Key functions:
uint16_t isoadc2_read_adc ( void )Function for reading 12bit ADC datauint16_t isoadc2_get_mv ( uint16_t adc_data )Function for converting ADC to mV data
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 IsoAdc2 Click example
*
* # Description
* This is an example that demonstrates the use of the ISO ADC 2 Click board.
*
* The demo application is composed of two sections :
*
* ## Application Init
* Initialization of SPI module and additional GPIO pins.
*
* ## Application Task
* Every second reads ADC data and voltage in mV and logs result.
*
* @author Stefan Ilic
*
*/
#include "board.h"
#include "log.h"
#include "isoadc2.h"
static isoadc2_t isoadc2;
static log_t logger;
void application_init ( void ) {
log_cfg_t log_cfg; /**< Logger config object. */
isoadc2_cfg_t isoadc2_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.
isoadc2_cfg_setup( &isoadc2_cfg );
ISOADC2_MAP_MIKROBUS( isoadc2_cfg, MIKROBUS_1 );
err_t init_flag = isoadc2_init( &isoadc2, &isoadc2_cfg );
if ( SPI_MASTER_ERROR == init_flag ) {
log_error( &logger, " Application Init Error. " );
log_info( &logger, " Please, run program again... " );
for ( ; ; );
}
log_info( &logger, " Application Task " );
}
void application_task ( void ) {
uint16_t rx_data;
uint16_t mv_data;
isoadc2_read_adc( &isoadc2, &rx_data );
Delay_ms ( 100 );
isoadc2_get_mv( &isoadc2, &mv_data );
log_printf( &logger, " ADC: %d \r\n", rx_data );
log_printf( &logger, " VIN: %d mV\r\n", mv_data );
log_printf( &logger, "---------------\r\n" );
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
Additional Support
Resources
Category:ADC
