Advanced heart monitoring with MCP609 and PIC32MZ2048EFM100

ECG Click is based on two MCP609s, a micropower CMOS operational amplifier from Microchip. These are unity-gain stable, rail-to-rail output swing operational amplifiers with a low offset voltage and input bias current designed to prevent phase reversal when the input pins exceed the supply voltages. ECG Click has a seven-block design. It comprises ESD, overvoltage and overcurrent protection (protecting both the hardware and the user), a pre-amplifier and amplifier, two high-pass filters, a low-pass filter, and a DRL circuit. When the electrical signal from the heart reaches the skin's surface, it becomes significantly faint, measuring only a few millivolts. However, this weak signal faces further obstruction due to muscle activity originating from different body parts. Additionally, electromagnetic interference from the surrounding environment, where the body can act as an antenna, presents another noise source. An onboard 3.5mm phone jack connects cables/electrodes to the Click board™.

The electrode collects voltage from the skin, after which the signal is amplified and filtered and then sent to the analog AN pin of the host MCU over the mikroBUS™ socket. The three electrodes should be placed on the left arm, right arm, and the left side of the abdomen (below the heart), on the left leg. ECG Click has one jumper and a trimmer potentiometer for setting the output voltage to match the input voltage level of the ADC, which will be used (10-bit ADC - 12-bit recommended). As a reference, it uses the MAX6106, a low-cost, micropower, low-dropout, high-output-current voltage reference from Analog Devices. The SMD (0805) jumper determines its output voltage range. When connecting all three electrodes, the output should be a constant voltage (1.024V or 2.048V, depending on the jumper position). The trimmer potentiometer is for adjusting the gain. So, if you set the jumper to the 2.048 position (zero is now 1.024V), the gain will be set so that the ECG

waveform is in the range of 0-2.048V. If you set the jumper to the 4.096 position (zero is now 2.048V), the gain will be set so that the ECG waveform is in the range of 0-4.096V. The final measurement results can be displayed as an Electrocardiogram using a free app, the MikroPlot, a free data visualization tool (Windows). It's a simple tool to help you visualize sensor data recorded over time, suitable for biosignals (ECG, EEG, EMG) and environmental data logging (temperature, humidity, and more). The app can receive data sets from a microcontroller through a USB UART connection. This Click board™ can only be operated with a 5V logic voltage level. The board must perform appropriate logic voltage level conversion before using MCUs with different logic levels. However, the Click board™ comes equipped with a library containing functions and an example code that can be used, as a reference, for further development.

Curiosity PIC32 MZ EF development board is a fully integrated 32-bit development platform featuring the high-performance PIC32MZ EF Series (PIC32MZ2048EFM) that has a 2MB Flash, 512KB RAM, integrated FPU, Crypto accelerator, and excellent connectivity options. It includes an integrated programmer and debugger, requiring no additional hardware. Users can expand

functionality through MIKROE mikroBUS™ Click™ adapter boards, add Ethernet connectivity with the Microchip PHY daughter board, add WiFi connectivity capability using the Microchip expansions boards, and add audio input and output capability with Microchip audio daughter boards. These boards are fully integrated into PIC32’s powerful software framework, MPLAB Harmony,

which provides a flexible and modular interface to application development a rich set of inter-operable software stacks (TCP-IP, USB), and easy-to-use features. The Curiosity PIC32 MZ EF development board offers expansion capabilities making it an excellent choice for a rapid prototyping board in Connectivity, IOT, and general-purpose applications.