Heart rate detection architecture
There is provided a system architecture including a PPG hardware module and a MEMS hardware module. The PPG hardware module processes PPG raw data, which is generally composed of analog signals or digital signals. The PPG hardware module filters the raw data for later digital calculation to, for example, find out frequency signals with higher peak values. The PPG hardware module then outputs the selected frequency signals to an MCU for heart rate calculation. The MEMS hardware module receives MEMS raw data from a motion detector made of MEMS elements. The MEMS raw data represents motion status of a user that could possibly affect the heart rate determination result. The MEMS hardware module filters the raw data for later digital calculation to find out frequency signals with higher peak values caused by motion.
1. A heart rate detection device, comprising:
a photoplethysmography (PPG) hardware module configured to receive PPG raw data and comprising a bandpass filter configured to filter the PPG raw data, the PPG hardware module further configured to generate PPG frequency data and first frequency domain information comprising a first frequency index set and a first spectrum value set associated with the first frequency index set;
a microelectromechanical systems (MEMS) hardware module configured to receive MEMS raw data and comprising a bandpass filter to filter the MEMS raw data, the MEMS hardware module further configured to generate MEMS frequency data and second frequency domain information including a second frequency index set and a second spectrum value set associated with the second frequency index set; and
a microcontroller unit (MCU), electrically coupled to the PPG hardware module and the MEMS hardware module, and configured to estimate a heart rate according to the PPG frequency data in referencing the MEMS frequency data by
determining a reference index according to a frequency index corresponding to a spectrum peak value in the second frequency domain information,
determining a denoising parameter according to the reference index,
removing spectrum values in the first frequency domain information corresponding to the reference index and nearby reference indexes according to the denoising parameter to generate denoised first frequency domain information, and
calculating the heart rate according to a spectrum peak value of the denoised first frequency domain information,
wherein the PPG hardware module and the MEMS hardware module respectively output the PPG frequency data and the MEMS frequency data without MCU operation to share loading of the MCU, and
wherein the estimated heart rate is configured to be shown on a display.
2. The heart rate detection device as claimed in claim 1 , wherein the MCU is further configured to calibrate the estimated heart rate according to a local oscillation frequency of the heart rate detection device and an external oscillation frequency received from an external host.
3. The heart rate detection device as claimed in claim 1 , wherein the MCU is further configured to generate a confidence level of the PPG frequency data, wherein the confidence level depends on a number of peak values in the PPG frequency data larger than a predetermined threshold.
4. The heart rate detection device as claimed in claim 1 , wherein the MCU is further configured to determine an airborne status according to at least one of the PPG frequency data and the MEMS frequency data.
5. The heart rate detection device as claimed in claim 1 , wherein the MCU is further configured to perform at least one of a sensor input setting, a first heart rate output setting, a heart rate estimation model setting, a heart rate filter setting and a heart rate tracking setting.
6. The heart rate detection device as claimed in claim 5 , wherein the MCU is further configured to output a motion state according to the MEMS frequency data.
7. The heart rate detection device as claimed in claim 6 , wherein the motion state is configured to determine at least one of the heart rate estimation model setting and the heart rate tracking setting.
8. The heart rate detection device as claimed in claim 1 , wherein
the PPG hardware module is further configured to receive the MEMS raw data from the MEMS hardware module to convert the received MEMS raw data to the MEMS frequency data at first, and then
the MCU is further configured to receive both the PPG frequency data and the MEMS frequency data from the PPG hardware module.
9. The heart rate detection device as claimed in claim 1 , wherein
the PPG hardware module is further configured to receive the MEMS raw data from the MEMS hardware module via the MCU to convert the received MEMS raw data to the MEMS frequency data at first, and then
the MCU is further configured to receive both the PPG frequency data and the MEMS frequency data from the PPG hardware module.
10. The heart rate detection device as claimed in claim 1 , wherein
the MEMS hardware module is configured to send the MEMS raw data to a bus line at first,
the PPG hardware module is further configured to receive the MEMS raw data from the bus line to convert the received MEMS raw data to the MEMS frequency data, and then
the MCU is further configured to receive both the PPG frequency data and the MEMS frequency data from the PPG hardware module.
11. The heart rate detection device as claimed in claim 1 , wherein the PPG hardware module is further configured to search peak values among the PPG frequency data.
12. The heart rate detection device as claimed in claim 1 , wherein the MEMS hardware module is further configured to search peak values among the MEMS frequency data.
13. A heart rate detection device, configured to receive a photoplethysmography (PPG) raw data from a PPG detector and a microelectromechanical systems (MEMS) raw data from a MEMS accelerometer, the heart rate detection device comprising:
a PPG hardware module configured to receive the PPG raw data, the PPG hardware module comprising:
a first bandpass filter configured to filter the PPG raw data;
a first conversion module configured to convert the filtered PPG raw data to PPG spectrum values and PPG frequency index; and
a first peak extraction module configured to search PPG peak spectrum values among the PPG spectrum values, and output the PPG peak spectrum values and the PPG frequency index;
a MEMS hardware module configured to receive the MEMS raw data, the MEMS hardware module comprising:
a second bandpass filter configured to filter the MEMS raw data;
a second conversion module configured to convert the filtered MEMS raw data to MEMS spectrum values and MEMS frequency index; and
a second peak extraction module configured to search a MEMS peak spectrum value among the MEMS spectrum values, and output the MEMS peak spectrum values and the MEMS frequency index; and
a microcontroller unit (MCU), electrically coupled to the PPG hardware module and the MEMS hardware module, and configured to estimate a heart rate according to the PPG peak spectrum values, the PPG frequency index, the MEMS peak spectrum values and the MEMS frequency index by
determining a reference index according to a frequency index corresponding to the MEMS peak spectrum value in the MEMS spectrum values,
determining a denoising range according to the reference index,
removing the PPG spectrum values in the PPG spectrum values corresponding to the denoising range to generate denoised PPG frequency data, and
calculating the heart rate according to a PPG peak spectrum value of the denoised PPG frequency data,
wherein the PPG hardware module outputs the PPG peak spectrum values as well as the PPG frequency index and the MEMS hardware module outputs the MEMS peak spectrum value as well as the MEMS frequency index without MCU operation to share loading of the MCU, and
wherein the estimated heart rate is configured to be shown on a display.
14. The heart rate detection device as claimed in claim 13 , wherein the first and second conversion modules are configured to perform fast Fourier transform.
15. The heart rate detection device as claimed in claim 13 , wherein a pass band of the first and second bandpass filters is between 0.5 Hz and 4 Hz.