Oximeter 2 Click

How does it work?

Oximeter 2 Click is based on the ADPD144RI, a highly integrated, photometric front end optimized for photoplethysmography (PPG) detection of blood oxygenation from Analog Devices. It combines highly efficient, red and infrared LED emitters, with 660nm red and 880nm IR wavelengths, and a sensitive 4-channel photodiode with a custom ASIC that provides optical isolation between the integrated LED emitters and the detection photodiodes to improve the signal-to-noise ratio. It uses synchronous detection of optical pulses to enhance the rejection of ambient light in addition to low power consumption.

The Oximeter 2 Click is designed for ultralow direct optical reflections, with independent AFE settings per channel and I2C control interface. The integrated LED emitters produce light pulses synchronous with the active sampling period of the AFE, which consisting of a programmable TIA, a band-pass filter, and an integrator. The processed analog signals are digitized by a 14-bit ADC and summed by the 20-bit burst accumulator. Four simultaneous sampling channels are matrixed into two independent time slots (one for each LED wavelength). An adjustable number of pulses per sample, accumulation, and averaging can be applied to multiple samples to increase the dynamic range to 27 bits.

Oximeter 2 Click communicates with MCU using the standard I2C 2-Wire interface, with a typical clock frequency of 400kHz. A high-speed I2C interface allows data to be read from output registers directly or through a FIFO buffer. All register writes are single word only and require 16 bits of data. It also comes with a programmable interrupt line, labeled as INT and routed on the INT pin of the mikroBUS™ socket that simplifies timely data access. The ADPD144RI does not require a specific Power-Up sequence but requires a supply voltage of 1.8V in order to work properly. Therefore, a small regulating LDO is used, the ADP160 from Analog Devices, providing a 1.8V out of 3.3V mikroBUS™ rail.

This Click board™ is designed to be operated only with a 3.3V logic voltage level. A proper logic voltage level conversion should be performed before the Click board™ is used with MCUs with different logic levels. However, Mikroe equipped its users with a library that contains functions and an example code that can be used, as a reference, for further development.

Specifications

Pinout diagram

This table shows how the pinout on Oximeter 2 Click corresponds to the pinout on the mikroBUS™ socket (the latter shown in the two middle columns).

Notes	Pin					Pin	Notes
	NC	1	AN	PWM	16	NC
	NC	2	RST	INT	15	INT	Interrupt
	NC	3	CS	RX	14	NC
	NC	4	SCK	TX	13	NC
	NC	5	MISO	SCL	12	SCL	I2C Clock
	NC	6	MOSI	SDA	11	SDA	I2C Data
Power Supply	3.3V	7	3.3V	5V	10	NC
Ground	GND	8	GND	GND	9	GND	Ground

Onboard settings and indicators

Oximeter 2 Click electrical specifications

Software Support

We provide a library for the Oximeter 2 Click as well as a demo application (example), developed using MikroElektronika compilers. The demo can run on all the main MikroElektronika development boards.

Package can be downloaded/installed directly form compilers IDE(recommended way), or downloaded from our LibStock, or found on mikroE github account.

Library Description

This library contains API for Oximeter 2 Click driver.

Key functions:

• void oximeter2_cfg_setup ( oximeter2_cfg_t *cfg ); – Config Object Initialization function.
• OXIMETER2_RETVAL oximeter2_init ( oximeter2_t *ctx, oximeter2_cfg_t *cfg ); – Initialization function.

Examples description

This application collects data from the sensor, calculates it and then logs the result.

The demo application is composed of two sections :

void oximeter2_write_res ( uint32_t data_write )
{
    log_printf( &logger, "%urn", data_write );
}

void oximeter2_logs_results( void )
{
    uint8_t final_result;
    
    oximeter2_read_data( &oximeter2, &res_slot[ 0 ] );

    log_printf( &logger, "Average result per photodiode is: rn" );
    
    switch ( oximeter2.enabled_channel )
    {
        case OXIMETER2_CH3_CH4_SELECTED:
        {
            log_printf( &logger, "PD3: " );
            oximeter2_write_res( res_slot[ 2 ] );
            log_printf( &logger, "PD4: " );
            oximeter2_write_res( res_slot[ 3 ] );

            final_result = ( res_slot[ 2 ] + res_slot[ 3 ] ) / 1000;
            break;
        }
        case OXIMETER2_ALL_CHANNELS_SELECTED:
        {
            log_printf( &logger, "PD1: " );
            oximeter2_write_res( res_slot[ 0 ] );
            log_printf( &logger, "PD2: " );
            oximeter2_write_res( res_slot[ 1 ] );
            log_printf( &logger, "PD3: " );
            oximeter2_write_res( res_slot[ 2 ] );
            log_printf( &logger, "PD4: " );
            oximeter2_write_res( res_slot[ 3 ]);

            final_result = ( res_slot[ 0 ] + res_slot [ 1 ] + res_slot[ 2 ] + res_slot[ 3 ] ) / 1000;
            break;
        }
        default:
        {
            break;
        }
    }
    
    if (final_result > 100)
    {
        final_result = 100;
    }
    log_printf( &logger, "Average result, in percentage: %urn", ( uint16_t )final_result );
    log_printf( &logger, "-------------------------rn" );

    Delay_ms( 300 );
}

void application_task ( void )
{
    oximeter2_logs_results();
}

The full application code, and ready to use projects can be installed directly form compilers IDE(recommneded) or found on LibStock page or mikroE GitHub accaunt.

Other mikroE Libraries used in the example:

• MikroSDK.Board
• MikroSDK.Log
• Click.Oximeter2

Additional notes and informations

Depending on the development board you are using, you may need USB UART click, USB UART 2 click or RS232 click to connect to your PC, for development systems with no UART to USB interface available on the board. The terminal available in all MikroElektronika compilers, or any other terminal application of your choice, can be used to read the message.

mikroSDK

This Click board™ is supported with mikroSDK – MikroElektronika Software Development Kit. To ensure proper operation of mikroSDK compliant Click board™ demo applications, mikroSDK should be downloaded from the LibStock and installed for the compiler you are using.

For more information about mikroSDK, visit the official page.