Feature #589

Enhanced I/O events

Added by Thomas Schöpping 3 months ago.

Status:NewStart date:2019-03-08
Priority:NormalDue date:
Assignee:-% Done:


Category:-Estimated time:4.00 hours
Target version:-


Currently I/O interrupts result in I/O events and propagate the causing EXTI line via event flags (e.g. EXTI #3 propagates (1 << 3) = 0x00000008). Since EXTI lines can aggregate multiple I/O pins (e.g. PA3 and PC3) this method can result in ambiguous events, because only the EXTI line but not the actual pin is specified.

To solve this issue, I/O events should not propagate plain eventflags_t data, but a struct like

struct {
  uint32_t flags : 24; // alternatively 28
  uint32_t pin   :  8; // alternatively  4
Since there is no EXTI hardware so far which provides more than 24 lines this solution is feasible. Alternatively the ratio can be set to 28:4 assuming that there will not be more than 2^4-1 pins aggregated in a single EXTI line. The -1 is important here, since the value of pin = 0 must be reserved to indicate ambiguity. This was the new method is compatible to plain eventflags_t and there might be cases where the exact pin can not be determined.
The determination can be realized within the ISR, which is called by the EXTI driver.

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