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Welcome to blog 3 of Neonatal Incubator Monitoring System. In this blog, we will learn how to interface the sensors with the PSoC 62S4 pioneer kit and write a simple interface example program for Ambient Light & Temperature, Heart Rate sensor, Interface with ESP32, and Interface with IoT sense expansion kit with the PSoC62S4.
Hardware Requirements
To follow this tutorial, you will need:
- PSoC62S4 Pioneer Kit
- ESP32 Dev board
- MAX30102 Heart Rate Sensor
- IoT sense expansion kit
Ambient Light & Temperature Sensor Interface
The Ambient Light & Temperature Sensor is used for monitoring the environment of the incubator. The PSoC62S4 pioneer kit has an onboard ambient light sensor {P10.7} and a temperature sensor {P10[4], P10[5] and P10[6]}. Run the following example for the ambient light & temperature application.
#include "cy_pdl.h"
#include "cyhal.h"
#include "cybsp.h"
#include "cy_retarget_io.h"
#include "math.h"
/*******************************************************************************
* Macros
********************************************************************************/
/* Defines for the ADC channels */
#define THERMISTOR_SENSOR_CHANNEL (1)
#define REF_RESISTOR_CHANNEL (0)
#define ALS_SENSOR_CHANNEL (2)
/* Number of channels used */
#define CHANNEL_COUNT (3)
/* Reference resistor in series with the thermistor is of 10kohm */
#define R_REFERENCE (float)(10000)
/* Beta constant of NCP18XH103F03RB thermistor is 3380 Kelvin. See the thermistor
data sheet for more details. */
#define B_CONSTANT (float)(3380)
/* Resistance of the thermistor is 10K at 25 degrees C (from the data sheet)
Therefore R0 = 10000 Ohm, and T0 = 298.15 Kelvin, which gives
R_INFINITY = R0 e^(-B_CONSTANT / T0) = 0.1192855 */
#define R_INFINITY (float)(0.1192855)
/* Zero Kelvin in degree C */
#define ABSOLUTE_ZERO (float)(-273.15)
/* ALS offset in Percent */
/* To configure this value, begin with offset of 0 and note down the lowest ALS
percent value. Configure the ALS_OFFSET with the lowest observed ALS percent. */
#define ALS_OFFSET (20)
/* ALS low threshold value - if ALS percentage is lower than this value, user
* LED is turned ON */
#define ALS_LOW_THRESHOLD (45)
/* ALS high threshold value - if ALS percentage is higher than this value, user
* LED is turned OFF */
#define ALS_HIGH_THRESHOLD (55)
/*******************************************************************************
* Function Prototypes
********************************************************************************/
/* Function to convert the measured voltage in the thermistor circuit into
* temperature */
double get_temperature(int32 therm_count, int32 ref_count);
/* Function to convert the measured voltage in the ALS circuit into percentage */
uint8 get_light_intensity(int32 adc_count);
/* IIR Filter implementation */
int32 low_pass_filter(int32 input, uint8 data_source);
/* FIFO Interrupt Handler */
void sar_fifo_interrupt_handler(void);
/* Function to initialize analog resources */
/* Resources include SAR ADC and its associated FIFO, analog references and
deep sleep resources */
void init_analog_resources(void);
/*******************************************************************************
* Global Variables
********************************************************************************/
/* IIR Filter variables */
int32 filt_var[CHANNEL_COUNT];
/* FIFO interrupt configuration structure */
/* Source is set to FIFO 0 and Priority as 7 */
const cy_stc_sysint_t fifo_irq_cfg = {
.intrSrc = (IRQn_Type) pass_interrupt_fifo_0_IRQn,
.intrPriority = 7
};
/* This flag is set in the FIFO interrupt handler */
volatile uint8 fifo_intr_flag = false;
/*******************************************************************************
* Function Name: main
********************************************************************************
* Summary:
* This is the main function for CM4 CPU. It initializes the ADC, does the
* measurement of thermistor and ALS and sends the data over UART.
*
* Parameters:
* void
*
* Return:
* int
*
*******************************************************************************/
int main(void)
{
/* Configure P6[5] - JTAG Data to Analog High Z to avoid leakage current */
/* This pin is logic high by default which causes leakage current on CY8CKIT-062S4 Pioneer Kit. */
cyhal_gpio_configure(P6_5, CYHAL_GPIO_DIR_OUTPUT, CYHAL_GPIO_DRIVE_ANALOG);
/* Variable to capture return value of functions */
cy_rslt_t result;
/* FIFO read structure */
cy_stc_sar_fifo_read_t fifo_data = {0};
/* Variable for filtered reference voltage (thermistor circuit) and als data */
int32 filtered_data[CHANNEL_COUNT];
/* Temperature value in deg C */
double temperature;
/* Light intensity in percentage */
uint8 light_intensity;
/* Variable to initialize IIR filter for the first iteration */
uint8 first_run[CHANNEL_COUNT]= {true, true, true};
/* Variable for number of samples accumulated in FIFO */
uint8 data_count;
uint16 display_delay = 0;
/* Initialize the device and board peripherals */
result = cybsp_init() ;
if (result != CY_RSLT_SUCCESS)
{
CY_ASSERT(0);
}
/* Initialize the debug uart */
result = cy_retarget_io_init(CYBSP_DEBUG_UART_TX, CYBSP_DEBUG_UART_RX,
CY_RETARGET_IO_BAUDRATE);
if (result != CY_RSLT_SUCCESS)
{
CY_ASSERT(0);
}
/* Print message */
/* \x1b[2J\x1b[;H - ANSI ESC sequence for clear screen */
printf("\x1b[2J\x1b[;H");
printf("---------------------------------------------------------------------------\r\n");
printf("PSoC 6 MCU: SAR ADC Low-Power Sensing - Thermistor and Ambient Light Sensor\r\n");
printf("---------------------------------------------------------------------------\r\n\n");
printf("Touch the thermistor and block/increase the light over the ambient light \r\n");
printf("sensor to observe change in the readings. \r\n\n");
/* Initialize and enable analog resources */
init_analog_resources();
/* Configure the LED pin */
result = cyhal_gpio_init(CYBSP_USER_LED2, CYHAL_GPIO_DIR_OUTPUT , CYHAL_GPIO_DRIVE_STRONG, CYBSP_LED_STATE_OFF);
if (result != CY_RSLT_SUCCESS)
{
CY_ASSERT(0);
}
/* Enable the global interrupt */
__enable_irq();
/* Enable the timer to start the sampling process */
/* Using the device configurator, trigger interval from the timer is
* set to 2.5ms which results in effective scan rate of 400sps for the SAR ADC.
*/
Cy_SysAnalog_TimerEnable(PASS);
for (;;)
{
/* Wait till printf completes the UART transfer */
while(cyhal_uart_is_tx_active(&cy_retarget_io_uart_obj) == true);
/* Put the device to deep-sleep mode. Device wakes up with the level interrupt from FIFO.
With the effective scan rate of 400sps, level count of 120 and 3 channels, device
wakes up every 120/(400*3) seconds, that is, 100ms. */
Cy_SysPm_CpuEnterDeepSleep(CY_SYSPM_WAIT_FOR_INTERRUPT);
/* Check if the interrupt is from the FIFO */
if(fifo_intr_flag)
{
/* Clear the flag */
fifo_intr_flag = false;
/* Check how many entries to be read. Should be equal to (LEVEL+1) when level
* interrupt is enabled */
data_count = Cy_SAR_FifoGetDataCount(SAR0);
/* Take all the readings from the FIFO and feed through IIR Filter */
while(data_count > 0)
{
data_count--;
/* Read the FIFO */
Cy_SAR_FifoRead(SAR0, &fifo_data);
/* If it is the first time reading the data, initialize the IIR filter
* variable and result variable */
if(first_run[fifo_data.channel] == true)
{
filtered_data[fifo_data.channel] = fifo_data.value;
filt_var[fifo_data.channel] = fifo_data.value << 8;
/* Clear the flag */
first_run[fifo_data.channel] = false;
}
else /* Push the data to the IIR filter */
filtered_data[fifo_data.channel] = low_pass_filter((int16)fifo_data.value, fifo_data.channel);
}
/* Calculate the temperature value */
temperature = get_temperature(filtered_data[THERMISTOR_SENSOR_CHANNEL], filtered_data[REF_RESISTOR_CHANNEL]);
/* Calculate the ambient light intensity in percentage */
light_intensity = get_light_intensity(filtered_data[ALS_SENSOR_CHANNEL]);
/* Control the LED */
if(light_intensity < ALS_LOW_THRESHOLD)
cyhal_gpio_write(CYBSP_USER_LED2, CYBSP_LED_STATE_ON);
else
if(light_intensity > ALS_HIGH_THRESHOLD)
cyhal_gpio_write(CYBSP_USER_LED2, CYBSP_LED_STATE_OFF);
/* Send over UART every 500ms */
if(display_delay == 4)
{
/* Print the temperature and the ambient light value*/
printf("Temperature: %2.1lfC Ambient Light: %d%%\r\n", temperature, light_intensity);
/* Clear the counter */
display_delay = false;
}
else /* Increment the counter */
display_delay++;
}
}
}
/*******************************************************************************
* Function Name: init_analog_resources
********************************************************************************
* Summary:
* This function initializes the analog resources such as SAR ADC, reference block,
* and deep sleep resources.
*
* Parameters:
* None
*
* Return:
* None
*
*******************************************************************************/
void init_analog_resources()
{
/* Variable to capture return value of functions */
cy_rslt_t result;
/* Initialize AREF */
result = Cy_SysAnalog_Init(&pass_0_aref_0_config);
if (result != CY_RSLT_SUCCESS)
{
CY_ASSERT(0);
}
/* Initialize deep sleep resources - Timer, LPOSC */
result = Cy_SysAnalog_DeepSleepInit(PASS, &cy_cfg_pass0_deep_sleep_config);
if (result != CY_RSLT_SUCCESS)
{
CY_ASSERT(0);
}
/* Enable AREF */
Cy_SysAnalog_Enable();
/* Enable Low-Power Oscillator */
Cy_SysAnalog_LpOscEnable(PASS);
/* Initialize the SAR ADC; it includes initialization of FIFO */
result = Cy_SAR_Init(SAR0, &pass_0_saradc_0_sar_0_config);
if (result != CY_RSLT_SUCCESS)
{
CY_ASSERT(0);
}
/* Initialize common resources for SAR ADCs in the pass block.
Common resources include simultaneous trigger parameters, scan count
and power up delay */
result = Cy_SAR_CommonInit(PASS, &pass_0_saradc_0_config);
if (result != CY_RSLT_SUCCESS)
{
CY_ASSERT(0);
}
/* Enable SAR block */
Cy_SAR_Enable(SAR0);
/* Enable the FIFO Level Interrupt mask */
Cy_SAR_SetFifoInterruptMask(SAR0, CY_SAR_INTR_FIFO_LEVEL);
/* Configure the interrupt and provide the ISR address. */
(void)Cy_SysInt_Init(&fifo_irq_cfg, sar_fifo_interrupt_handler);
/* Enable the interrupt. */
NVIC_EnableIRQ(fifo_irq_cfg.intrSrc);
}
/*******************************************************************************
* Function Name: get_temperature
********************************************************************************
* Summary:
* This function calculates the temperature in degree celsius.
*
* Parameters:
* ADC results for thermistor and reference resistor voltages
*
* Return:
* temperature in degree celsius (float)
*
*******************************************************************************/
double get_temperature(int32 therm_count, int32 ref_count)
{
double temperature;
double rThermistor;
/* Calculate the thermistor resistance */
rThermistor = (double)therm_count * R_REFERENCE / ref_count;
/* Calculate the temperature in deg C */
temperature = (double)(B_CONSTANT/(logf(rThermistor/R_INFINITY))) + ABSOLUTE_ZERO;
return(temperature);
}
/*******************************************************************************
* Function Name: get_light_intensity
********************************************************************************
* Summary:
* This function calculates the ambient light intensity in terms of percentage.
*
* Parameters:
* ADC measurement result of the photo-transistor
*
* Return:
* ambient light intensity in percentage (uint8: 0 - 100)
*
*******************************************************************************/
uint8 get_light_intensity(int32 adc_count)
{
int16 als_level;
if(adc_count < 0)
adc_count = 0;
/* Calculate the ambient light intensity in terms of percentage */
/* Adjust the shift parameter for the required sensitivity */
als_level = ((adc_count * 100)>>10) - ALS_OFFSET;
/* Limit the values between 0 and 100 */
if(als_level > 100)
als_level = 100;
if(als_level < 0)
als_level = 0;
return((uint8)als_level);
}
/*******************************************************************************
* Function Name: low_pass_filter
********************************************************************************
* Summary:
* This function implements IIR filter for each SAR channel data. Cut-off frequency
* is given by F0 = Fs / (2 * pi * a) where, a is the attenuation constant and Fs
* is the sample rate, that is, 400 sps.
*
* In this function, for thermistor and reference resistor channel, a = 256/160 and
* cut-off frequency is approximately 40Hz; for ALS, a=256/4, cut-off frequency is
* approximately 1Hz.
*
* Parameters:
* Data to be filtered and the data source.
*
* Return:
* Filtered data
*
*******************************************************************************/
int32 low_pass_filter(int32 input, uint8 data_source)
{
int32 k;
input <<= 8;
switch(data_source)
{
case THERMISTOR_SENSOR_CHANNEL:
filt_var[THERMISTOR_SENSOR_CHANNEL] = filt_var[THERMISTOR_SENSOR_CHANNEL] + (((input-filt_var[THERMISTOR_SENSOR_CHANNEL]) >> 8) * 160);
k = (filt_var[THERMISTOR_SENSOR_CHANNEL]>>8) + ((filt_var[THERMISTOR_SENSOR_CHANNEL] & 0x00000080) >> 7);
break;
case REF_RESISTOR_CHANNEL:
filt_var[REF_RESISTOR_CHANNEL] = filt_var[REF_RESISTOR_CHANNEL] + (((input-filt_var[REF_RESISTOR_CHANNEL]) >> 8) * 160);
k = (filt_var[REF_RESISTOR_CHANNEL]>>8) + ((filt_var[REF_RESISTOR_CHANNEL] & 0x00000080) >> 7);
break;
case ALS_SENSOR_CHANNEL:
filt_var[ALS_SENSOR_CHANNEL] = filt_var[ALS_SENSOR_CHANNEL] + (((input-filt_var[ALS_SENSOR_CHANNEL]) >> 8) * 4);
k = (filt_var[ALS_SENSOR_CHANNEL]>>8) + ((filt_var[ALS_SENSOR_CHANNEL] & 0x00000080) >> 7);
break;
default:
k = 0;
break;
}
return k;
}
/*******************************************************************************
* Function Name: sar_fifo_interrupt_handler
********************************************************************************
* Summary:
* This function is the handler for FIFO level interrupt
*
* Parameters:
* None
*
* Return:
* None
*
*******************************************************************************/
void sar_fifo_interrupt_handler()
{
/* Clear the FIFO interrupt */
Cy_SAR_ClearFifoInterrupt(SAR0, CY_SAR_INTR_FIFO_LEVEL);
/* Set the flag */
fifo_intr_flag = true;
}
Interfacing the MAX30102 Heart Rate Sensor
The Heart-rate and the SpO2 levels of the baby are monitored using the MAX30102. The MAX30102 pulse oximeter and heart rate sensor is an I2C-based low-power plug-and-play biometric sensor. Connect the Heart Rate sensor module to the I2C pins of the PSoC62S4 Pioneer Kit using jumper wires.
/*******************************************************************************
* File Name: main.c
*
* Description: This example project demonstrates the basic operation of the
* I2C resource as Master using HAL APIs. The I2C master sends the
* command packets to the I2C slave to control an user LED.
*
* Related Document: See README.md
*
*
********************************************************************************
* Copyright 2019-2023, Cypress Semiconductor Corporation (an Infineon company) or
* an affiliate of Cypress Semiconductor Corporation. All rights reserved.
*
* This software, including source code, documentation and related
* materials ("Software") is owned by Cypress Semiconductor Corporation
* or one of its affiliates ("Cypress") and is protected by and subject to
* worldwide patent protection (United States and foreign),
* United States copyright laws and international treaty provisions.
* Therefore, you may use this Software only as provided in the license
* agreement accompanying the software package from which you
* obtained this Software ("EULA").
* If no EULA applies, Cypress hereby grants you a personal, non-exclusive,
* non-transferable license to copy, modify, and compile the Software
* source code solely for use in connection with Cypress's
* integrated circuit products. Any reproduction, modification, translation,
* compilation, or representation of this Software except as specified
* above is prohibited without the express written permission of Cypress.
*
* Disclaimer: THIS SOFTWARE IS PROVIDED AS-IS, WITH NO WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, NONINFRINGEMENT, IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. Cypress
* reserves the right to make changes to the Software without notice. Cypress
* does not assume any liability arising out of the application or use of the
* Software or any product or circuit described in the Software. Cypress does
* not authorize its products for use in any products where a malfunction or
* failure of the Cypress product may reasonably be expected to result in
* significant property damage, injury or death ("High Risk Product"). By
* including Cypress's product in a High Risk Product, the manufacturer
* of such system or application assumes all risk of such use and in doing
* so agrees to indemnify Cypress against all liability.
*******************************************************************************/
/*******************************************************************************
* Header Files
*******************************************************************************/
#include "cyhal.h"
#include "cybsp.h"
#include "cy_retarget_io.h"
#include "cy_pdl.h"
#include "stdio.h"
#define I2C_MASTER_ADDRESS 0x57
#define HRM_FIFO_ADDRESS 0x05
#define HRM_FIFO_RD_PTR_ADDRESS 0x04
#define HRM_MODE_CONFIG_ADDRESS 0x09
cy_rslt_t result;
cyhal_i2c_t i2c_master;
uint8_t readBuffer[6];
uint8_t writeBuffer[2];
uint32_t hrmData = 0;
/*******************************************************************************
* Macros
*******************************************************************************/
/* Delay of 1000ms between commands */
#define CMD_TO_CMD_DELAY (1000UL)
/* Packet positions */
#define PACKET_SOP_POS (0UL)
#define PACKET_CMD_POS (1UL)
#define PACKET_EOP_POS (2UL)
/* Start and end of packet markers */
#define PACKET_SOP (0x01UL)
#define PACKET_EOP (0x17UL)
/* I2C slave address to communicate with */
#define I2C_SLAVE_ADDR (0x24UL)
/* I2C bus frequency */
#define I2C_FREQ (400000UL)
/* Command valid status */
#define STATUS_CMD_DONE (0x00UL)
/* Packet size */
#define PACKET_SIZE (3UL)
/*******************************************************************************
* Global Variables
*******************************************************************************/
/*******************************************************************************
* Function Prototypes
*******************************************************************************/
/*******************************************************************************
* Function Definitions
*******************************************************************************/
/*******************************************************************************
* Function Name: handle_error
********************************************************************************
* Summary:
* User defined error handling function
*
* Parameters:
* uint32_t status - status indicates success or failure
*
* Return:
* void
*
*******************************************************************************/
void handle_error(uint32_t status)
{
if (status != CY_RSLT_SUCCESS)
{
CY_ASSERT(0);
}
}
void i2c_write(uint8_t address, uint8_t value)
{
writeBuffer[0] = address;
writeBuffer[1] = value;
cyhal_i2c_master_write(&i2c_master, I2C_MASTER_ADDRESS, writeBuffer, 2, 0, true);
}
uint8_t i2c_read(uint8_t address)
{
uint8_t value;
cyhal_i2c_master_write(&i2c_master, I2C_MASTER_ADDRESS, &address, 1, 0, true);
cyhal_i2c_master_read(&i2c_master, I2C_MASTER_ADDRESS, &value, 1,0, false);
return value;
}
void hrm_init()
{
i2c_write(HRM_MODE_CONFIG_ADDRESS, 0x03); // Enable HR and SPO2 sensors
}
uint32_t hrm_read_data()
{
uint8_t read_pointer = i2c_read(HRM_FIFO_RD_PTR_ADDRESS);
uint8_t fifo_data = i2c_read(HRM_FIFO_ADDRESS);
uint8_t num_samples = (read_pointer - fifo_data + 32) % 32;
if (num_samples == 0) return 0;
uint8_t sample_data[6 * num_samples];
cyhal_i2c_master_write(&i2c_master, I2C_MASTER_ADDRESS, HRM_FIFO_ADDRESS, 1,0, true);
cyhal_i2c_master_read(&i2c_master, I2C_MASTER_ADDRESS, sample_data, 6 * num_samples, 0, false);
uint32_t sum = 0;
for (int i = 0; i < num_samples; i++)
{
uint32_t value = ((uint32_t)sample_data[i * 6 + 3] << 16) | ((uint32_t)sample_data[i * 6 + 4] << 8) | sample_data[i * 6 + 5];
sum += value;
}
uint32_t average = sum / num_samples;
return average;
}
/*******************************************************************************
* Function Name: main
********************************************************************************
* Summary:
* This is the main function.
* 1. I2C Master sends command packet to the slave
* 2. I2C Master reads the response packet to generate the next command
*
* Parameters:
* void
*
* Return:
* int
*
*******************************************************************************/
int main(void)
{
printf("Heart Rate Sensor Data", hrmData);
cyhal_i2c_cfg_t i2c_config;
i2c_config.frequencyhal_hz = 100000;
i2c_config.is_slave = false;
result = cyhal_i2c_init(&i2c_master, CYBSP_I2C_SDA, CYBSP_I2C_SCL, NULL);
if (result != CY_RSLT_SUCCESS) return -1;
result = cyhal_i2c_configure(&i2c_master, &i2c_config);
if (result != CY_RSLT_SUCCESS) return -1;
hrm_init();
while (1)
{
hrmData = hrm_read_data();
printf("Heart Rate: %lu\n", hrmData);
cyhal_system_delay_ms(1000);
}
}
Interfacing ESP32
Connect the ESP32 microcontroller to the UART pins of the PSoC62S4 Pioneer Kit using jumper cables. We will be sending all the sensor data to the ESP32 over serial. The data will be sent to the dashboard over HTTP or MQTT broker.
/* Print sensor data on serial */
printf("Heart Rate: %d bpm\r\n", hrmData);
printf("SpO2: %d%%\r\n", spo2);
printf("Temperature: %2.1lfC\r\n",temperature);
printf("Ambient Light: %d%%\r\n", light_intensity);
Interfacing the IoT Sense Expansion Kit
The Sensor data and interface require an OLED display. We use the IoT sense expansion kit, a low-cost Arduino UNO compatible shield board that can be used to easily interface a variety of sensors with the PSoC 6 MCU platform, specifically targeted for audio and machine learning applications. Connect the IoT Sense Expansion Kit to the PSoC62S4 Pioneer Kit using the Arduino Header pins.
I2C device address (7-bit) : OLED display (ACC6) -> 0x3C
SCL P6[0] I2C SCL (connected to PSoC and the I2C devices in the shield)
SDA P6[1] I2C SDA (connected to PSoC and the I2C devices in the shield)
Done!
In this blog, I have shown you how to interface with a Heart Rate sensor, Ambient Light & Temperature, ESP32 microcontroller, and IoT Sense Expansion Kit using the PSoC62S4 Pioneer Kit. This was fun, getting started with interfacing various sensors and external modules with the PSoC62S4 microcontroller. In the next blog, we will be configuring the dashboard. Thank you for reading, and please stay tuned for more updates.
