Design of Mobile Glucose Meter Monitoring System

Diabetes poses significant challenges to human health, often leading to complications such as hyperglycemia, cardiovascular disease, and kidney disease. Despite advancements in medical technology, a definitive cure for diabetes remains elusive. In response, the blood glucose meter was developed as a valuable tool. Its introduction enables patients to effectively monitor fluctuations in blood sugar levels, facilitating necessary adjustments to their diet, as well as their work and rest routines. In this article, TechSparks will explore the concept of designing a wireless blood glucose monitoring system. Our objective is to empower users with the ability to monitor their blood sugar levels conveniently and reliably anytime and anywhere, leveraging the capabilities of wireless networks.

Table of Contents

Wireless Blood Glucose Monitoring System Project Overview

The project revolves around the design of a blood glucose monitoring system that utilizes the MSP430 microprocessor and GSM mobile communication. The complete system comprises two essential components: the mobile phone monitoring system and the diabetes monitoring center. The accompanying diagram provides a concise overview of the project’s operational workflow. Patients can conveniently monitor their blood sugar levels using a mobile blood glucose meter, which enables them to upload the collected data to the GSM network. Subsequently, the network undertakes data deployment, and the monitoring center, in turn, delivers diagnostic feedback based on the received data.

System working mode

Mobile blood glucose detector: The designated mobile phone model is Motorol A388c, while the blood glucose meter primarily relies on the MSP430 single-chip microcomputer and enzyme electrode sensor. The mobile phone establishes a connection via a serial port, facilitating control and display of blood glucose test results through the mobile phone’s keyboard and LCD screen. Essentially, this function seamlessly integrates blood glucose monitoring into the mobile phone’s capabilities.

Monitoring Center: The hardware configuration comprises a server connected to an MC35 wireless communication module through a serial port. The software system is primarily responsible for overseeing MC35’s reception of text messages, as well as patient information management and maintenance.

Design Ideas of Mobile Blood Glucose Meter

System Hardware Design

The project encompasses the design of a blood glucose monitoring system based on the MSP430 microprocessor. It comprises several essential components, including the enzyme electrode sensor, signal processing, single-chip data acquisition and processing, and serial communication between the single-chip and mobile phone. The enzyme electrode sensor utilizes a three-electrode system, incorporating a reference electrode, a counter electrode, and a working electrode. The hardware system operates as follows:

The front-end signal processing controls the electrode access circuit through an analog switch, enabling different working states. Signal processing involves amplification and low-pass filtering of the sensor’s current signal, effectively eliminating high-frequency interference and ensuring high-quality signals for subsequent data acquisition circuits.

Data collection and serial port communication of the blood glucose concentration are facilitated by TI’s MSP430 series microcontroller, serving as the primary control unit for processing. Additionally, the system features temperature compensation functionality to mitigate the impact of ambient temperature on test results and enhance their accuracy.

The compact blood glucose testing module measures 3cm x 1cm, allowing seamless integration with the mobile phone case. This integration enhances portability and convenience for users, enabling them to perform blood glucose testing on the go.

Measuring Principle of Blood Glucose Concentration

The measurement of blood sugar concentration is carried out using a bio-enzyme electrode sensor. When blood is applied to the sensor, the glucose enzyme catalyzes the oxidation of the electron transfer material on the carbon electrode surface. The resulting oxidation current, generated during the oxidation-reduction reaction, exhibits a linear correlation with the glucose concentration. By measuring the intensity of this oxidation current, the blood sugar concentration can be calculated.

A constant working voltage of 0.4V is applied to the electrode. When the blood sample to be measured is placed on the electrode’s testing area, the immobilized glucose oxidase on the electrode undergoes a chemical reaction with the glucose in the blood sample. After a specific delay, the response current of the enzyme electrode shows a linear relationship with the glucose concentration in the measured blood sample.

Enzyme electrode current change curve

In correspondence to the blood glucose concentration ranging from 2.2-27.8mmol/L, the enzyme electrode exhibits a response current in the range of approximately 3-50μA. The blood glucose meter utilizes this correlation to calculate and display the concentration value of glucose in the blood sample. Analyzing the curve, it is observed that the reaction current on the enzyme electrode reaches its peak around 11s. Consequently, the system designates the first 11s as the reaction time of the enzyme electrode, while the last 5.3s is designated as the data collection time for the enzyme electrode. By integrating the current area over the duration of 5.3s, the electric quantity Q is obtained. Then, utilizing the known blood sugar concentration C0, the standard coefficient K can be derived using the following formula:

Q =∫I(t)dt = K C0
K = Q/ C0

Now find the tested blood glucose concentration:

Cx = Q/K

Temperature is a crucial factor that influences enzyme activity and the rate of enzyme-catalyzed reactions. Hence, to ensure measurement accuracy, temperature compensation is essential. Through comprehensive system testing and result analysis, the following temperature compensation formula has been derived:

Kt = 0.0133t + 0.067

Considering the temperature compensation, therefore, the blood glucose concentration calculation formula is as follows:

Cx = Q/(K ×Kt)

Communication Software Design

Java mobile phone operating systems universally support the J2ME MIDP1.0 Java standard, which is a development platform introduced by SUN for embedded consumer electronics products. Motorola388, A388C, and other Motorola mobile phones not only comply with the J2ME MIDP1.0 Java standard but also offer the Motorola SDK for J2ME, which implements specific interface functions provided by CLDC/MIDP.

Establishing a reliable and real-time connection between the mobile phone and the blood glucose meter via the serial port is crucial. Extensive experimentation has led to the adoption of a multi-threaded development approach, ensuring accurate and efficient data reception from the blood glucose meter to the mobile phone.

When creating a serial communication program, the package provides the Connector class along with the StreamConnection, InputStream, and OutputStream interfaces. In J2ME, connections are established using the open(String connect) method of the Connector class, allowing for different connections by passing appropriate parameters to the connect method.

Running on Motorola A388

  1. Packaging: Once the compilation is successful, use the Archive Builder feature in the JBuilder Wizard menu. Select “MIDlet” as the Archive type and follow the prompts to complete the packaging process.
  2. Running on PC: Run the MIDlet and update the packaged files: .jar and .jad.
  3. Downloading: Connect the mobile phone and the PC using the provided data cable. On the phone, select the “Download via Data Cable” menu option. Then, use the free pcjal.exe download tool provided by Motorola388 to easily transfer the MIDlet to the phone.
  4. Installation: After downloading a J2ME program on the phone, it will typically initiate the installation automatically. The program will be stored in the designated location on the phone.
  5. Running on Motorola A388C: Once the program is installed, it will appear in the application menu on the phone. Users can select the corresponding menu item to run the program. The interface is shown in Figure.
running interface

Diabetes Care Center System Design

The hardware components of the diabetes care center system primarily consist of a server connected to a GSM module. Specifically, the wireless module MC35 from SIEMENS Company is selected for this purpose. The hardware circuit can be divided into four main sections: power supply circuit, responsible for providing a 6V-12V power source; serial port circuit, enabling connectivity with the computer’s serial port; SIM card circuit, facilitating the connection between the SIM card and the module; and the MC35 module drive circuit, utilized to initialize and operate the MC35 wireless communication module.

The software system is depicted in the diagram below. The human-machine interface module has been enhanced to include a feature allowing manual data input by the user. The diabetes pathology database comprises a knowledge base, rule base, and differential diagnosis rules. Additionally, the patient information database is utilized to store the patient’s blood glucose measurement values and relevant background information. The system communicates with the GSM module using the serial communication protocol, while SMS management is carried out using the AT command.

System function block diagram

Results and Discussion

The mobile blood glucose meter is designed for easy operation. When conducting a test, the user enters the blood glucose test interface and clicks the “Run” button. The screen will prompt the user to insert the blood sample test strip, followed by a 15-second countdown. Once the countdown reaches “0,” the blood glucose concentration test result will be displayed. The test result can be directly sent to MA35I via the GSM network by clicking the “Send SMS” button. The remote diabetes diagnosis system then receives and stores the data, providing a diagnosis conclusion and feedback to the patient.

Currently, the most accurate measurement method is the venous blood test performed in hospitals. However, as this system aims for user convenience, a Johnson & Johnson blood glucose meter with relatively accurate measurements is selected.

The test results indicate that the maximum repeatability error of the mobile phone-based blood glucose meter is 1.01%, and the maximum relative error of the concentration is 5.98%. These values fall within the error range specified by medical device standards.

After testing the sending and receiving of text messages, the system operates normally. The measured data is compared with the knowledge base, and based on simple rules, an automatic diagnosis conclusion can be generated. Doctors also have the option to modify or add suggestions as needed.

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