[DISCUSSION] Async timer trait for Counting and Capture timer in embedded-hal-async

[Shaibal-Microsoft]

Hello Everyone,

This is my first open-source discussion. Apologies in case I am not aware of some etiquettes.

I wanted to propose following asynchronous trait in embedded-hal-async for HW timers which I have reviewed with respect to NXP RT6xx, STM32 and Infineon PSOC62 design its fitting correctly with the design. The requirements for the HW timer moduels are -

1 - User shall be able to start Counting Timer
2 - User shall be able to start Capture Timer for capturing timestamp for an event
3 - User shall be able to pass input event for capturing timestamp
4 - User shall be able to pass output event to capture timer match/capture event in a HW pin

TriggerInput -

1. Logical event space for input events. Used to capturing timer counter value
2. HW implementation needs to map from logical to physical event representation

TriggerOutput -

1. Logical event space for output events. Used to set a GPIO pin based on match or capture event
2. HW implementation needs to map from logical to physical event representation

// This super trait will be useful to access the logical timer ID
// An implementation can choose to implement a timer as a logical entity keeping HW details away from user. In that case, logical //entity is required to be identified with an ID field for later uses like resource release/cleanup once timer usage is completed.
// In case implementation chooses to expose HW details such as base address of the timer module, the get_id can be left blank or // return base address of the HW module
trait AsyncTimerId {
fn get_id(&self) -> usize;
}

pub trait AsyncTimer : AsyncTimerId {
/// Starts a timer with the specified count and event input/output.
/// # Arguments
/// * count - The count value for the timer.
/// * event_input - The event input for the timer.
/// * event_output - The event output for the timer.
/// This function takes event input and output as option to provide flexibility to user to use it or not.
fn start(&mut self, count: u32, event_input: Option, event_output: Option);

/// Waits asynchronously for the count/capture timer to complete or to record an event timestamp.
async fn wait(&mut self);

}

Please let me know in case I need to add more info.

Thanks and Regards
Shaibal