Design of wristband for monitoring physiological parameters of group exercise

In order to monitor the heart rate, blood oxygen saturation and blood pressure abnormalities of athletes during exercise and ensure the safety of athletes during exercise, this paper designs a group exercise physiological parameter monitoring bracelet. The safety thresholds of heart rate, blood oxygen saturation and blood pressure are set through the bracelet, and the heart rate, blood oxygen saturation and blood pressure data of the monitored person during exercise are obtained. If the physiological parameter data is detected outside the safety threshold, the bracelet will give an audible and visual alarm and a vibration prompt to warn the monitored person to make timely relief adjustments. At the same time, all the collected data information is summarized to the host computer through wireless transmission, and the data information is received in the remote monitoring system for information recording and analysis. The supervisor performs data classification and health assessment, and gives a health status assessment conclusion. When an unhealthy state occurs, a warning prompt or rescue information and alarm are issued.

1 Overall design plan

The hardware design of the lower computer uses STM32 as the main control device, connecting the wireless communication module sending end, physiological parameter detection module, power module, display module, and buzzer. The physiological parameter detection module collects the three-dimensional physiological parameters of the human body, transmits them to STM32 through the serial port, and converts the monitored multiple physiological parameter signals into digital signals and packages them, which are transmitted to the computer through the wireless transmission module sending end for recording and processing; the display module displays; when the detected data exceeds the threshold range, the LED and buzzer sound and light alarm. After the upper computer monitoring end is configured with the corresponding baud rate, it can read the data packet data from the wireless communication module receiving end, and then import the data into the software for health status assessment and display.

2 System Hardware Design

2.1 STM32 minimum system module circuit design

The main control device is the most critical module in the system, which requires a small size, low power consumption and strong performance. The STM32 series of microcontrollers are embedded controllers specially designed for embedded applications that require high performance, low cost and low power consumption. Taking comprehensive considerations into account, the STM32F103RCT6 processor is selected for this design of the group sports physiological parameter monitoring and health status assessment system. Its main function is to process, analyze and alarm the data measured by the sensor, and package multiple physiological parameter data and send them to the host computer through serial wireless transparent communication.

2.2 Design of physiological parameter detection module

JFH111 physiological parameter test module is a new type of multi-spectral physiological measurement module. It adopts front-end sensor technology, which can greatly improve the sensitivity and signal-to-noise ratio of the module. It also has the advantages of small size and low power consumption. The physiological index detection device of JFH111 is based on the fuzzy storage method of PPG photoelectric volume pulse wave recording method and non-penetrating blood pressure method, and can accurately record pulse waveform, heart rate, blood oxygen saturation, blood pressure and other information. This system is a multi-spectral physiological data acquisition module that can accurately measure pulse, heart rate, blood oxygen value and microcirculation. The system only needs to communicate with the module through serial port and can directly obtain test data. At the same time, this system has the characteristics of small size and low power consumption, which improves the service life of the bracelet. The STM32 main controller uses serial port to communicate with the module and can directly obtain measurement results from the data packet, which reduces the complexity of the abnormal monitoring and alarm system of multiple physiological parameters under human motion to a certain extent. JFH111 physiological parameter detection module is also equipped with host computer monitoring software.

2.3 Wireless Communication Module Circuit Design

The wireless communication module uses the HC-12 wireless 433 type, which uses TTL level to directly interact with STM32 and transmits data to the PC using radio waves. The MCU or PC transmits serial port data through the TXD interface, and the RXD interface receives the serial port data, and then transmits the data to the wireless communication module, which is restored to the serial port of the MCU or PC through the TXD interface. The HC-12 module replaces the physical connection in half-duplex communication. Each module can only work in half-duplex mode, and cannot receive and receive data at the same time, but can also perform reverse operations under certain conditions.

2.4 Display module circuit design

The system uses a 0.96-inch 7-wire OLED display and communicates through the SPI communication protocol. SPI is the abbreviation of serial peripheral device. It is a high-speed, full-duplex, synchronous communication bus. It has only 4 pins, which saves plugs and PCB space and convenience. Therefore, many chips use SPI. Commonly used OLED communications include IIC communication, but since this system needs to read more data and the IIC communication method uses 2 data lines, the communication data is slower, and the SPI communication method uses four data lines, and the communication data is faster. In this system, simulated SPI is used, that is, the GPIO port is used to simulate the SPI bus to communicate with the SSD1306 bus.

2.5 Other module circuit design

2.5.1 Power module circuit design

A correct and reliable power module is related to the performance of the entire system. The power management module used in this system uses a 1S lithium battery as the system battery. The standard voltage of the battery is 3.7 V. After being boosted by the power management module, it outputs 5 V to power the system. Capacitors are used inside the module to filter the power signal to ensure the quality of the power supply. At the same time, a self-recovery fuse circuit and a Zener diode circuit are designed in the circuit to ensure the safety of the power supply post-chip circuit.

2.5.2 Buzzer Circuit Design

The maximum output current of the I/O port of the STM32F103RCT6 master is 25 mA, while the buzzer needs 30 mA to sound. Therefore, an NPN transistor is used to increase the current and drive the buzzer. In order to prevent the buzzer from sounding by mistake, a 10 k resistor is connected between the base and emitter of the transistor, and the emitter is grounded. When the I/O port connected to the STM32 outputs a high level, the buzzer will sound to indicate an alarm, and when the output is a low level, the buzzer stops ringing.

3 System Software Design

3.1 Overall software design

The main program flow chart of the group sports physiological parameter monitoring bracelet is shown in the figure below. After startup, the system is powered on and initialized. The initialization function mainly includes the initialization of the system clock configuration and delay function, OLED, buzzer, LED, wireless communication module and detection module serial port, timer and interrupt priority. After the initialization is completed, the sensor offline detection subroutine is first entered to determine whether the JFH111 physiological parameter detection module detects human physiological parameters. If the physiological parameter detection module is not detected for a long time and there is no data transmitted to STM32, it means offline, and there is an audible and visual alarm prompt. If the physiological parameter detection module, the JFH111 detection module feeds back the detected data to STM32 for processing, and the STM32 processes the data and displays it on the OLED. If a physiological parameter data detected in the human body motion state exceeds the pre-set threshold range, an audible and visual alarm is issued, and the abnormal data and the monitored person information are wirelessly transmitted to the host computer for display.

3.2 Physiological parameter detection subroutine

The physiological parameter detection process can be divided into two parts. First, determine whether the sensor can work normally. When it is detected that the sensor can detect data normally, the detected data is analyzed and read.

The JFH111 detection module used in this system transmits the collected physiological index information to STM32 through the serial port. Since the detection requires a certain degree of tightness, it is necessary to determine whether the sensor and the STM32 microcontroller are connected normally before the detection. If they are not connected, the system will promptly alarm through the LED.

Since blood pressure data is updated slowly, only the heart rate and blood oxygen saturation data are collected to detect sensor offline. Set the sensor online detection flag, 1 for online, 0 for offline. After the system is turned on, put the skin in contact with the sensor to start detecting heart rate and blood oxygen saturation. When one of the heart rate and blood oxygen saturation data is detected to be 0, start scanning and counting. When the count exceeds 50, the sensor is judged to be offline and an audible and visual alarm is issued. Otherwise, the sensor is judged to be online and enter the data analysis subroutine. The JFH111 physiological parameter detection subroutine flow is shown in Figure 3.

3.3 Alarm subroutine

The alarm function is reflected in two aspects: detecting whether the sensor is offline and alarming when the threshold exceeds the value. After the system starts working, the LED and buzzer are initialized. First, it is determined whether the JFH111 detection module is successfully connected. If the JFH111 detection module is successfully connected, data detection is allowed to continue. If the JFH111 detection module is offline, the LED becomes brighter, showing a yellow light and flashing slowly, and the buzzer sounds intermittently. In the process of detecting physiological parameters, if the parameters are within the set threshold, it indicates a healthy state, the LED lights up green and flashes slowly, and the buzzer does not sound. If the detected parameters exceed the threshold, it indicates an unhealthy state, the LED lights up yellow and flashes quickly, and the buzzer sounds long.