From 195be43f5a241bd40332f8755f0dbbba8da40bc5 Mon Sep 17 00:00:00 2001 From: Gregg Date: Sat, 25 Jul 2020 08:47:05 -0500 Subject: [PATCH] Completed Example 5 --- examples/Intermediate/5-WorkingLED/DEV_LED.h | 68 +++++++++++++++++++- src/Settings.h | 21 +++--- 2 files changed, 79 insertions(+), 10 deletions(-) diff --git a/examples/Intermediate/5-WorkingLED/DEV_LED.h b/examples/Intermediate/5-WorkingLED/DEV_LED.h index 66d0420..f3ad550 100644 --- a/examples/Intermediate/5-WorkingLED/DEV_LED.h +++ b/examples/Intermediate/5-WorkingLED/DEV_LED.h @@ -25,7 +25,7 @@ struct DEV_LED : Service::LightBulb { // First we create a derived StatusCode update(){ - digitalWrite(ledPin,power->newValue.BOOL); // use a standard Arduino function to turn on/off ledPin based on the boolean variable power->newValue.BOOL + digitalWrite(ledPin,power->newValue.BOOL); // use a standard Arduino function to turn on/off ledPin based on the boolean variable power->newValue.BOOL (see below for more info) return(StatusCode::OK); // return OK status code. There are other possibilties we will explore in later examples. @@ -33,3 +33,69 @@ struct DEV_LED : Service::LightBulb { // First we create a derived }; ////////////////////////////////// + +// How update() works: +// +// Whenever a HomeKit controller requests HomeSpan to update a Characteristic, HomeSpan calls the update() method for the SERVICE that contains the +// Characteristic. It calls this only one time, even if multiple Characteristics updates are requested for that Service. For example, if you +// direct HomeKit to turn on a light and set it to 50% brightness, it will send HomeSpan two requests: one to update the "On" Characteristic of the +// LightBulb Service from "false" to "true" nd another to update the "Brightness" Characteristic of that same Service to 50. This is VERY inefficient +// and would require the user to process multiple updates to the same Service. +// +// Instead, HomeSpan combines both requests into a single call to update() for the Service itself, where you can process all of thre Characteristics +// that change at the same time. In the example above, we only have a single Characteristic to deal with, so this does not mean much. But in later +// examples we'll see how this works with multiple Characteristics. + +// How to access Characteristic values: +// +// HomeSpan stores the values for its Characteristics in a union structure that allows for different types. The current value of a Characteristic +// is stored in a union named "value" whereas upon an update request, the requested value is stored in a union named "newValue." To access the data +// underlying either "value" or "newValue" you need to select the element of the union that matches the type. This is arguably sloppy, but using +// C++ templates did not seem to make the process any less cumbersome. The names of each element are based on those specified in HAP Table 6-5, and map +// to the Arduino data types as follows: +// +// BOOL -> (boolean) +// UINT8 -> (uint8_t) +// UINT16 -> (uint16_t) +// UINT32 -> (uint32_t) +// UINT64 -> (uint64_t) +// INT -> (int) +// FLOAT -> (double) +// STRING -> (const char *) +// +// In the above example we created pointer named "power" to point to our newly-created "On" Characteristic. Hence, to access the current value of that +// Characteristic we use "power->value.BOOL" To access to new value requested by HomeKit for this update, we use "power->newValue.BOOL" as shown above. +// In most cases, we can manage the update by just reading the newValue requested, regardless of the whatever the current value is, but access to the +// current value is available if neeed. + +// How to determine the value type for any Characteristic: +// +// All HomeKit Characteristics that have been implemented in HomeSpan are defined in "Services.h" in the HomeSpan library. The top part of "Services.h" defines +// all the implemented Services. The bottom part defines the collection of Characteristics needed for those Services. Within the definition of each +// Characteristic you'll see the HAP ID number, as well as the data type, such as (boolean), (uint16_t), etc. Select the corresponding element name +// from the table above to access the underlying "value" or "newValue" data elements. + +// What the return code means: +// +// HomeKit requires each Characteristic to return a status code when an attempt to update it's value is made. HomeSpan automatically takes care of +// some of errors, such as a Characteristic not being found, or a request to update a Characteristic that is read only. In these cases update() is never +// even called. But if it is, HomeSpan will apply the return code you specify to each of the Characteristics that were to be updated in that Service. +// By returning StatusCode:OK you tell HomeSpan that the newValues requested are okay and you've made the required updates to the physical device. Upon +// receiving an OK status, HomeSpan updates the Characteristics themselves by copying the "newValue" data elements into the current "value" data elements. +// HomeSpan then sends a message back to HomeKit letting it know that the new values it requested have been sucessfully processed. At no point does +// HomeKit as for, or allow, a value to be sent back from HomeSpan indicating the data in a Characteristic. When requesting an update, HomeKit simply +// expects an okay or not okay. +// +// If for some reason the update() code cannot process an update request, it must return a HAP error code. These are listing in Settings.h. As noted above, +// some are created automatically by HomeSpan and update() is never called. Others can only be determined from within an update() call and should be +// used as the return value. The StatusCodes that can be used in this fashion are: OK, Unable, Busy. Any of the other StatusCode listed in Settings.h +// are automatically handled by HomeSpan and should not be used as a return code, though nothing bad happens if you do. This is because the +// HomeKit application itself only seems to distinguish an "OK" status code from a an not-"OK" code. HomeKit does not seem to process any error code +// differently from any other error code. All error codes lead HomeKit to simply say "Device Not Reponding" in the Controller. This suggests that the +// differences between "Unable" and "Busy" don't mean anything to HomeKit. They are all interpreted as an error, so pick anyone you'd like in the event +// you can't update a characteristic to the requested value. Note that when you do return an error code, HomeSpan will NOT copy the newValue data elements +// requested into the the current value data elements, thus keeping all Characteristics in the Service unchanged. +// +// Final note: There are very few reasons you should need to return an error code since so much checking is done in advance by either HomeSpan or HomeKit +// itself. For instance, HomeKit does not allow you to use the Controller, or even Siri, to change the brightness of LightBulb to a value outside the +// range of allowable values you specified. This means that any update() requests you receive should only contain newValue data element that are in-range. diff --git a/src/Settings.h b/src/Settings.h index 80e164a..563b6ac 100644 --- a/src/Settings.h +++ b/src/Settings.h @@ -76,13 +76,16 @@ enum class Category { // Reference: HAP Table 6-11 // enum class StatusCode { - OK=0, - Unable=-70402, - Busy=-70403, - ReadOnly=-70404, - WriteOnly=-70405, - NotifyNotAllowed=-70406, - UnknownResource=-70409, - InvalidValue=-70410, - TBD=-1 // status To-Be-Determined (TBD) once service.update() called + + OK=0, // Can be returned by user in update() + Unable=-70402, // Can be returned by user in update() + Busy=-70403, // Can be returned by user in update() + + ReadOnly=-70404, // HomeSpan takes care of this internally + WriteOnly=-70405, // HomeSpan takes care of this internally + NotifyNotAllowed=-70406, // HomeSpan takes care of this internally + UnknownResource=-70409, // HomeSpan takes care of this internally + InvalidValue=-70410, // HomeSpan takes care of this internally + + TBD=-1 // status To-Be-Determined (TBD) once service.update() called - internal use only };