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Fully describe behavior of Pin.value() and Pin.value(x) in different modes, as well as clarificatiosn for other Pin methods.

Paul Sokolovsky 2015-11-03 19:37:05 +02:00
parent 526b060ae3
commit 41d3e3a9ad
1 changed files with 15 additions and 10 deletions
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25
Hardware-API.md

@ -147,19 +147,24 @@ As specified above, Pin class allows to set alternate function for particular pi
### Methods ### Methods
Do we really need 3 ways to set the value? TOD: Do we really need 2+ ways to set the value?
- `pin.init(...)` re init. - `pin.init(...)` - (Re)initinialize a pin, accepts the same parameters as constructor, except `id`.
- `pin.value()` NOHEAP; get value (returns 1 or 0). See the note below. - `pin.value()` NOHEAP - Get pin value (returns 1 or 0). Behavior depends on the mode of a pin:
- `pin.value(x)` NOHEAP; set value (value can be any valid Boolean expression) - `Pin.IN` - Returns the actual input value currently present on a pin.
- `pin()` NOHEAP; fast method to get the value of the pin. See the note below. - `Pin.OUT` - Undefined. MAY return value stored in the output buffer of a pin.
- `pin(value)` NOHEAP; fast method to set the value of the pin. - `Pin.OPEN_DRAIN` - If pin is in "0" state, undefined. MAY return value stored in the output buffer of a pin (i.e. 0). Or MAY return actual input value on a pin. Otherwise, if pin is in "1", MUST return actual input value on a pin. (Note that if open-drain pin is in 0 state, entire bus to which pin is connected, expected to be in 0 state, so there's little point to read actual input value; the only reason for another value in this case would be voltage conflict on a bus, which is usually a hardware malfunction and in some cases may lead to physical damage of a pin).
- `pin.toggle()` NOHEAP - `pin.value(x)` NOHEAP - Set output value of a pin (value can be any valid expression, which is cast to True/False valur for 1/0 output value respectively). Exact behavior depends on the pin mode:
- `Pin.IN` - Value is stored in the output buffer for a pin. Pin state doesn't change (it keeps being in high-impedance state, as required for IN mode). The stored value will become active on a pin as soon as it is changed to OUT or OPEN_DRAIN mode.
**Note:** When the mode is `Pin.OPEN_DRAIN`, it must be possible to read the input value of the Pin. - `Pin.OUT` - Pin is set to the `x` value immediately.
- `Pin.OPEN_DRAIN` - If value is "0", ping is set to low state. Otherwise, it is set to high-impedance state.
- `pin.out_value()` NOHEAP, optional - Return value stored in the output buffer of a pin, regardless of its mode.
- `pin()` NOHEAP - Fast method to get the value of the pin. Fully equivalent to `Pin.value()`.
- `pin(x)` NOHEAP - Fast method to set the value of the pin. Fully equivalent to `Pin.value(x)`.
- `pin.toggle()` NOHEAP, optional - Toggle output value of a pin.
**Getters and setters** **Getters and setters**
- `pin.id()` NOHEAP; get only. - need to clarify what this really returns. I'm assuming a board ID. - `pin.id()` NOHEAP; get only. - Return ID of a pin. This MAY return `id` as specified in the constructor. Or it MAY return "normalized" software-specific pin ID.
- `pin.mode([mode])` NOHEAP - `pin.mode([mode])` NOHEAP
- `pin.pull([pull])` NOHEAP - `pin.pull([pull])` NOHEAP
- `pin.drive([drive])` NOHEAP - `pin.drive([drive])` NOHEAP