I designed a PCB with a low power STM32 microcontroller, a low noise density biosensor from ST (although I just use its IMU), and an AD8232 for performing an Electrocardiogram (ECG). My microcontroller receives an external interrupt from the IMU when a new measurement is ready, it triggers a read using Direct Memory Access (DMA) for both the IMU and the Analog to Digital Converter (ADC) which reads the ECG almost perfectly in sync with the corresponding acceleration. I have implemented a slightly modified version of the Pan-Tompkins algorithm to detect the peaks of the R waves from the ECG and I am able to calculate instantaneous and moving average heart rate and heart rate variability. This data is streamed to my computer over a bare-metal USB Virtual COM port and is stored/plotted. I am getting started with filtering the signal from the IMU so I can mount the board on my chest and be able to get a clean Seismocardiogram (SCG).
Log in to leave a comment