I am going to realize a real time monitoring system for medical care and finally the system should make phone calls according to the severity of the result , I would like to know is it best to perform realtime signal processing on raspberry or stm , the processed signal is ECG and the processing will include denoising , segmentation , feature extraction , classification . I am using an ECG acquisition sensor ad8232 and I found while doing my research that stm32 provides a dsp unit(digital signal processor) , that raspberry pi is not suitable for realtime activities because it has no timer and so u need to add other components , also I found real time operating systems such as RTAI https://www.rtai.org/ that should work on raspberry's os what how can I choose ? an other question is does working on the os of the raspberry make this count as an embedded project ?
This sounds like a great project.
You should have a list of at least 20 processors from at least 10 companies that you are choosing from when starting a new project. Understand your requirements and make an informed decision.
You will find that most available processor manufacturers are careful about using their products in life critical systems. For example, STMicroelectronics health products brochure says
UNLESS EXPRESSLY APPROVED IN WRITING BY AN AUTHORIZED ST REPRESENTATIVE, ST PRODUCTS ARE NOT RECOMMENDED, AUTHORIZED OR WARRANTED FOR USE IN LIFE SAVING, OR LIFE SUSTAINING APPLICATIONS, NOR IN PRODUCTS OR SYSTEMS WHERE FAILURE OR MALFUNCTION MAY RESULT IN PERSONAL INJURY, DEATH, OR SEVERE PROPERTY OR ENVIRONMENTAL DAMAGE.
Most chip manufacturers have something similar.
This should not stop your project, but you should keep in mind that if you make enough progress, you will eventually need to use processors and components that can be certified for use in your country.