mirror of https://github.com/ARMmbed/mbed-os.git
874ff1fe22
On some targets like STM family boards with LPTIM enabled an interrupt is triggered on counter rollover. We need special handling for cases when next_match_timestamp < start_timestamp (interrupt is to be fired after rollover). In such case after first wake-up we need to reset interrupt and go back to sleep waiting for the valid one. On some targets like STM family boards with LPTIM enabled there is a required delay (~100 us) before we are able to reprogram LPTIM_COMPARE register back to back. This is handled by the low level lp ticker wrapper which uses LPTIM_CMPOK interrupt. CMPOK fires when LPTIM_COMPARE register can be safely reprogrammed again. This means that on these platforms we have additional interrupt (CMPOK) fired always ~100 us after programming lp ticker. Since this interrupt wake-ups the board from the sleep we need to go to sleep after CMPOK is handled. Background: There is an errata in LPTIM specification that explains that CMP Flag condition is not an exact match (COUNTER = MATCH) but rather a comparison (COUNTER >= MATCH). As a consequence the interrupt is firing early than expected when programing a timestamp after the 0xFFFF wrap-around. In order to work-around this issue, we implement the below work-around. In case timestamp is after the work-around, let's decide to program the CMP value to 0xFFFF, which is the wrap-around value. There would anyway be a wake-up at the time of wrap-around to let the OS update the system time. When the wrap-around interrupt happen, OS will check the current time and program again the timestamp to the proper value. |
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| .. | ||
| main.cpp | ||
| sleep_api_tests.h | ||
| sleep_test_utils.h | ||