Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Add implementation note for embassy-stm32's time-driver #2250

Merged
merged 1 commit into from
Dec 4, 2023
Merged

Add implementation note for embassy-stm32's time-driver #2250

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
11 changes: 11 additions & 0 deletions embassy-stm32/src/time_driver.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,17 @@ use crate::rtc::Rtc;
use crate::timer::sealed::{Basic16bitInstance as BasicInstance, GeneralPurpose16bitInstance as Instance};
use crate::{interrupt, peripherals};

// NOTE regarding ALARM_COUNT:
//
// As of 2023-12-04, this driver is implemented using CC1 as the halfway rollover interrupt, and any
// additional CC capabilities to provide timer alarms to embassy-time. embassy-time requires AT LEAST
// one alarm to be allocatable, which means timers that only have CC1, such as TIM16/TIM17, are not
// candidates for use as an embassy-time driver provider.
//
// The values of ALARM_COUNT below are not the TOTAL CC registers available, but rather the number
// available after reserving CC1 for regular time keeping. For example, TIM2 has four CC registers:
// CC1, CC2, CC3, and CC4, so it can provide ALARM_COUNT = 3.

#[cfg(not(any(time_driver_tim12, time_driver_tim15)))]
const ALARM_COUNT: usize = 3;

Expand Down