Pulse oximeter presentation

PULSEOXIMETER

Digital Health And Bioinformatic Engineering Embedded Systems A.A. 2019/2020

CONFIGURATION

Useful to set The user can enter a thresholds to have new configuration or correct readings use an existing one. If a new configuration is provided, it overrides the previous one, stored in the EEPROM parameters.

DATA ACQUISITION

Pressing the user MAX30100 acquire button the data acquisition starts. If the average sample is exceeded, the buzzer shown on LCD emits a sound.

LOG MESSAGES

Each 10 seconds a status message is printed on UART to show the current status date and time. The status message is also sent via MQTT.

HARDWARE SCHEMA

• STM32F401RE
• PO MAX30100
• LCD1602
• RTC DS1307
• WIFI ESP8266
• EEPROM AT24C256
• Passive buzzer

Board logic levels 3.3V. Connection to 3.3V power. Resistor for the LCD contrast and for the LCD led.

CONNECTIONS

LCD led connection to 5V to increase backlight.

of devices that use I²C, to the same 2 pins, to create a single master-multiple slaves connection

Loop to acquire PO data

Filters to remove noise from PO raw data

Global variable used to detect if the button has been pressed and two loops used to check if the button has been pressed or not

Structures to store configuration and datetime

SOFTWARE ARCHITECTURES

Use PWM to control passive buzzer tones

Creation of a circular buffer for USART, since the USART usually use only one byte, but here some parameters have variable length

Creation of a personalized ISR because default callback cannot use a circular buffer

EEPROM initialized to 0xFF

ESP8266 equipped with a default firmware