Add methods to enable/disable the entire timer

[justacec]

I am submitting this simple PR to start discussion on the recently opened issue #182. I have simply renamed the existing enable and disable methods to be channel_enable and channel_disable. I have also added two new methods, enable/disable, which would then be expected to be used to enable/disable the entire timer.

I think that this functionality is useful so that one does not need to temporarily store the current duty for each channel in order to "disable" the timer. The state would be maintained and it results in a single read/write to the timer control registers.

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @therealprof (or someone else) soon.

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[ryankurte]

cc. @rust-embedded/hal, if this change is desirable perhaps we should break this in the v1 migration? (the caveat being this has not been demonstrated as per the new hal guidelines)

[therealprof]

I think the desire to have this came up in stm32-rs/stm32f1xx-hal#176 .

[therealprof]

@justacec Would you mind fixing the conflicts?

[therealprof]

Ping @justacec.

[therealprof]

@justacec Are you still around?

[justacec]

@therealprof Working on it now.

[justacec]

@therealprof Ok, I think I synced this up. As I was updating this PR, I was not sure if the other "channel" specific methods (such as try_get_duty) should be changed to try_get_duty_channel when called from the Pwm object. That name makes sense for the PwmPin, but maybe not intuitive enough for the Pwm object.

[therealprof]

Looks good to me. Any objections @ryankurte?

[ryankurte]

Looks good to me! Even though it is rather straightforward I think it would still be good to demonstrate an implementation / driver, as well as to add this change to the changelog.

[justacec]

@ryankurte I just updated the changelog as requested. As for the implementation, I suppose that would need to be done in the stm32f1xx_hal crate.

[ryankurte]

has anyone had a chance to implement this? would be excellent to get it merged ^_^