cpu/cc2538: RTT: implement missing API functions#14700
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benpicco merged 3 commits intoRIOT-OS:masterfrom Aug 7, 2020
Merged
cpu/cc2538: RTT: implement missing API functions#14700benpicco merged 3 commits intoRIOT-OS:masterfrom
benpicco merged 3 commits intoRIOT-OS:masterfrom
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We can't set the hardware counter directly, so always add an offset.
We can't read back the alarm, so just store it in a variable.
Previously the setting the alarm would overwrite the overflow callback and vice versa. Since we can only set one alarm in hardware, always set the alarm to the closest event of the two.
fjmolinas
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The overhead is just a few instructions and if those functions are useful after all, we might as well add them.
It's a pity there are no tests for those / the API is not clear here.
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Contribution description
This PR is a takeover of #13630, rest of the description is as in the original PR, I only removed comments made in #13630 (review). This PR should help addressing #13686 since the application does not compile because of the missing functions.
The RTT implementation of
cpu/cc2538is based on the sleep timer, a 32 bit 32kHz timer that can only be read and that only supports one alarm. (No overflow interrupt)This implements functions that are defined by the RIOT API, but are not directly supported by the hardware:
rtt_set_counter(): as we can't set the counter directly, add an offset to the raw counter value insteadrtt_get_alarm(): we can't read back the alarm time, so store it in a local variable. This is also needed forrtt_set_overflow_cb(): In the previous implementation the overflow callback would always overwrite the alarm callback and vice versa.To fix this, check which event will occur first and set that alarm as well as a flag to tell which alarm it was.
When the alarm rings, set the alarm to the other event if there is one.
Testing procedure
There are no tests for those functions.
Issues/PRs references
I implemented those for #13519, but then discovered I don't need them.
So I'm not sure if this should be added just for completeness' sake when we could just as well do without.