I didn't have time to post anything worth it this week.
To give a side view of my last post about software classes, here is a link to DO-178B on wikipedia. It is the reference about software embarked in aircrafts.
If you take time to read this document, you will see that it goes very further than what we have today in IEC 62304. The constraints about design on high classes are very very hard to respect. That's normal, when you think that software is used in flight commands and other stuff in the cockpit.
It has some side effects, mainly to stretch software development projects, and to ban software from some parts of the plane, for cost-driven reasons.
For example, a microcontroler plus software plus electric motors would be perfect to memorize and retreive the position settings of the pilot's seat. But the cost to develop such software is very high, as the pilot's seat is seen as a critical component. Aircraft manufacturers prefer replacing software and microcontroler by good old analogic electronics to do the same task on some models.
In my humble opinion, the constraints of the two highest classes for software in aircrafts would be to high for medical devices. There is always a pratician, or an emergency medical service, able to "catch" the patient if something goes wrong. Whereas there is nobody to "catch" a falling plane if its flight commands fail. The consequences of risks are far higher in aircrafts, with potentially hundreds of victims in an accident.
That is why classes A, B and C, and their design constraints are enough for medical devices.
Next week, I'll talk about exemptions of ISO13485 for standalone software medical devices.