Good afternoon, seniors.
I'm learning about Z-Wave and have some Z-Wave specifications.
But they are not sufficient to understand Open-Zwave concept..
Especially, the principle of Polling and State machine in Open-Zwave is so hard for me to understand..
Could you explain to me about it? or Could I get some documents or pictures for it?
Polling
Polling is simply when the controller sends a message to a device requesting its current status (on/off, current temperature, etc.). When a controller first starts up, it polls all the devices that are present in its configuration file. After startup, it's often no longer necessary to poll a device unless it's an older Z-Wave device or the manufacturer is concerned about implementing functionality that is patented by another company. Most current Z-Wave devices are configured to automatically report their statuses at regular user-defined intervals. Battery-powered Z-Wave devices that sleep a majority of the time, such as a motion/temperature/humidity sensor, cannot be polled when they're asleep. Most wake up at scheduled (user-defined) intervals and send a message to the controller that they are awake. They typically report their current status at that time. If the controller sends a polling request to a sleeping device,it's added to the queue of messages that are transmitted to the device when it informs the controller that it is awake. Some battery-powered devices don't always sleep and can be polled, such as some door locks.
State Machine
The Z-Wave state machine is the method used by Z-Wave to enable devices to be polled. When the controller wants to communicate with a device, it passes the Z-Wave frame to be sent, which sets the machine in the BEGIN state. The controller transmits the frame and enters the WAIT state. If the controller receives a valid response to its transmission, it enters the END state and begins communicating with the device. If no response is received after a timeout period, it enters the ERR state and retries the transmission. After a maximum of three ERR states, Z-Wave returns a NULL. it looks something like this:
In August 2016, Sigma Designs released most of the Z-Wave specification to the public, with resources for developers who want to include Z-Wave in their applications. Prior to August 2016, the specification was closely guarded. You can read more about the Z-Wave Public Specification here.
Related
When the device is in confirmed mode, it waits for a downlink confirmation (ACK) from the network after each uplink. If the confirmation is not received by the device, it will repeat (up to a maximum of 8 times and increasing the SF of the UL if it was lowered before) the uplink until it receives a confirmation. It may take about 30 seconds to send the 8 repetitions.
If the device does not see a confirmation and needs to send another uplink (e.g. alarm or new periodic measurement), it will send the new uplink and forget the previous one. To operate in confirmed mode, the device must be declared in confirmed mode (or ACK) on the network platform. You can activate it via the IoT configurator in the network parameters
Be aware that this operation consumes much more battery power than a traditional operation, even more, if the network quality is poor.
If the transmitter loses a lot of frames, it would be better to reposition the transmitter (if possible) or the GW (if possible) to improve the transmission rather than activating the ACK which will drain the battery faster than "expected" depending on the network condition.
Is this answer correct or not?
The app I worked on got an alert from apple wallet: "Some passes are receiving too many updates, which may affect battery life. Automatic updates for *** passes will be disabled. Choose RE-enable if you want automatic updates to continue." I only have 2 passes in the wallet from that app.
Does anyone know what's the reason trigger this alert? If we send 2 push notifications within 5 seconds, will that trigger this kind of alert?
It means pretty much what it says. Apple is respectful of user's battery life and data consumption and recognises that a pass update is a high energy activity that the user has little control over, and so if a pass issuer makes too many updates, then iOS takes action to alert the device owner so they can choose if they would like to continue to receive these updates (at the expense of reduced battery life).
Apple's previous policy was to silently throttle updates, but this led to problems, since users were unaware that they were being throttled and would wonder why their passes were not updating.
Apple recognises that developers may need to push content more frequently, which is why you can disable rate limiting on your device via the developer menu (that appears when you have your iPhone hooked up to Xcode).
Apple doesn't publish the criteria that it uses to throttle, and normally a quick burst of activity (E.g. a one-off burst of 2 or 3 messages in the space of a few minutes) would be tolerated. But if the issuer is sending dozens of messages every few minutes, then you can almost certainly expect they will see this message.
App that I am working on is offering a VPN connection, that can run even when the app is not running at all. This service is paid, but also I would like to offer a free trial limited by session length and maximum data transfered.
The problem I've encoutered, is with monitoring the data trasnfered when the app is in background or not runing at all. So far the best solution I've came up with, would be to periodically run small task that checks if the user is still within the data limit and if not, the VPN will be disconnected and notification shown to the user.
Will silent notification get priority every time it will be required? According to this quote from developer.apple.com, they are low-priority which isn't what I need, but I was unable to find anything else.
Silent notifications are not meant as a way to keep your app awake in the background, nor are they meant for high priority updates. APNs treats silent notifications as low priority and may throttle their delivery altogether if the total number becomes excessive. The actual limits are dynamic and can change based on conditions, but try not to send more than a few notifications per hour.
How can this be done reliably? Is there any other way?
If this is a personal VPN connection (i.e. you're just providing a config to the standard system) and you're not in the flow, then this isn't possible. There is intentionally no "I want my program to run all the time" solution. Even if you come up with one, Apple will probably shut you down.
If you're writing an MDM/supervised VPN connection (i.e. you're providing a ...Flow object of your own), then you're already running all the time and you can just control it as you want. I'm assuming you have the former or you wouldn't be asking.
I believe you're doing this backwards. Monitor the session length on the server, and disconnect there. When you disconnect, send a push notification, which can display a message directly without having to open the app. That is both robust and the intended solution.
Periodically posting a silent notification to wake yourself up will definitely not work because Apple specifically does not want you to do that and they explicitly break it (as they note "silent notifications are not meant as a way to keep your app awake in the background"). It's bad for battery life. This is intended to be solved on your sever, on on the user's device.
Preamble
I wrote a mobile application which should show upcoming events. The app downloads it's data from server. Data is prepared in batches once every 24 hours and it's ready to be fetched after 4 am. This gives me a perfect opportunity to sync it overnight and to make new data immediately available when the user opens the app.
Background fetch
This was my first approach for syncing data with the server. It's advertised as very powerful feature, but using it alone (out of the test environment) is not enough:
There is no way to force background fetches to execute at exact intervals.
I thought that the frequency of background fetch operations could be configured
// Setup background fetch
let timeIntervalEveryHour: NSTimeInterval = 3600
let sharedApp = UIApplication.sharedApplication()
sharedApp.setMinimumBackgroundFetchInterval(timeIntervalEveryHour)
but it's still dynamic and I think it is never for users who did't use app very often.
If 'Background App Refresh' is disabled, which automatically happen if device is in 'Low power mode', background fetch won't be triggered.
Other problems like Data Protection when device is locked and 30 seconds window for completion of all tasks are considered.
Remote (silent) notifications
So I took the next step and configured the server to post silent notifications once the batch is ready just to found that this is also not enough:
If application is force killed by the user or device is rebooted, notification won't be handled.
Rate limits. Delivery will be delayed, this depends on a variety of factors that are not explicitly specified by Apple, but probably - battery life, whether phone is on cellular, etc.
Sometimes silent push notifications are dispatched when application starts, which could lead to race conditions with the check for manual synchronisation. So I'll try to force it by adding "alert" = ""; to payload. (As it is suggested here)
Silent Push notifications could be disabled by the user be setting off 'Background App Refresh' - source
Manual synchronisation
To be sure that data is always up to date, if it's not recently updated, when app comes to foreground user is presented with alert which asks for manual synchronisation. Also it could be started later from settings tab. Unfortunately, according to analytics, most of the fetch requests are made manually.
First run case is also handled.
Next steps
I'm considering using VOIP notification. They should wake the app even if it's force killed. However I'm concerned that that would cause app get rejected.
Questions
Is there something I'm missing? I know that background synchronisation depends on a variety of factors, there could be no internet connection and etc, but is there any way to make it more reliable?
We are working in a groupon-like app where alerts are displayed to the user when he/she enters in the range of an offer.
The client insists on having alerts even when the app is in the background.
Due to the architecture of the system, the app gets the location of the client at intervals and checks with the server if there is any new alert. If so, the app does some processing in the local database and displays a notification.
APN cannot be used since changes in the server are out of reach for this project.
My question is whether Apple would accept it in AppleStore as I have read different opinions about it and Apple discourages its use as in this extract from iOS Developer Library
http://developer.apple.com/library/ios/#documentation/userexperience/conceptual/LocationAwarenessPG/CoreLocation/CoreLocation.html
At wake-up time, your app is put into the background and given a small amount of time to process the location data. Because your app is in the background, it should do minimal work and avoid any tasks (such as querying the network) that might prevent it from returning before the allocated time expires. If it does not, your app may be terminated
Thanks
How often does your app get location from the user? According to Apple's Background Execution and Multitasking, if you are getting the location updates on a regular schedule (I think it's less than 10 minutes), your app can still process in the background if you add location to UIBackgroundModes in your info.plist. With those CLLocation coordinates, you can then process your web service requests.
I personally have not done something like this, so I can't tell you for sure if Apple will reject your app or not. However, if everything is within the guideline and requirements set by Apple, I don't see why they would reject your app.
EDIT:
From the Apple doc:
An app that provides continuous location updates to the user (even
when in the background) can enable background location services by
including the UIBackgroundModes key (with the location value) in its
Info.plist file. The inclusion of this value in the UIBackgroundModes
key does not preclude the system from suspending the app, but it does
tell the system that it should wake up the app whenever there is new
location data to deliver. Thus, this key effectively lets the app run
in the background to process location updates whenever they occur.
I guess even if the app is suspended, it will wake up whenever there is a new location data to deliver.
I think you should reconsider your approach for this application. It sounds like you have decided to build a set of features which are not necessarily well informed by, or a good fit for, the characteristics of the devices the app will run on.
You write that "the app gets the location every n minutes" but that's not how iOS location services work. Querying location services for the current location occasionally is a good approach when your app is running in the foreground but that's not an option once it is suspended or terminated. Instead you need to subscribe to location events, at some level of accuracy, and your app will be notified when the device's location changes. There are no guarantees about the schedule on which you receive these events and it varies depending on the accuracy you request and the speed at which the device is moving.
Additionally, obtaining a location is an expensive operation and can quickly drain the device's battery. Burning through a user's available battery power in an hour or two is a very good way to get your app uninstalled quickly. Where possible you should be using the significant location change service to get low accuracy location updates with minimal power consumption. If you need more precision then consider using boundary crossing events for a defined region or at least reduce the accuracy your have requested as much as possible.
With all that out of the way you still need to work within the limited time your app has to run once started by a location update. That's probably not long enough to make a round trip to the server. If a network connection is already active and the device happens to have low latency you will probably get a response some of the time but I would expect to see the app terminated by the OS frequently. When that happens I don't know that you will continue to receive location updates which might otherwise re-launch the app.
Instead of downloading a list of alerts and displaying them locally a better solution might be to attempt to send your current location to the server via UDP when you see a significant location change. That way you can fire off a network request without waiting for a response. Only some of those requests will still succeed but at least your app won't be terminated. You can then process the locations you receive on the server and send push notifications when appropriate.
I realize that you don't seem to be able to make server side changes. In that case the best you might be able to do is pre-fetch alerts for the nearby region when the app runs (and if you ever manage to complete a round-trip while in the background). That way you could compare location updates to that list and not need to fire off a network request on every location update. Unfortunately it sounds like you might be backed into a corner here with no reliable solution available under your current constraints.