I've done a lot of reading about LE Bluetooth and GATT but I'm still struggling to fully understand what GATT is. To make it simple I'd like to express how I'd like my app to work, and simply be told if it's possible or not? The basic premise is it will be used as a location tracker and beacons (maybe iBeacons specifically) will be placed around the building and whenever you enter the range of the beacon a message will be sent to the server from the phone. The idea is that it doesn't need to scan, the phone just simply listens and whenever a beacon advertises, the phones in range will hear this and raise an event.
Scenario:
Client downloads the app and enters the building for the first time.
The building has a beacon in every room, advertising every 5 seconds for example.
When the client walks into a room and is in range of a beacon, the phone will get an unfriendlier version of the message "Beacon 2 has an RSSI of -87".
When they leave the room they will no longer hear the message and so will do nothing until it hears another message from a beacon.
NOTE: This scenario doesn't involve any scanning, looping or pairing. The phone will just know it has to listen for LE Bluetooth messages.
So, is this possible? From what I've seen it seems like you need to scan and connect with each beacon using GATT before you can receive data from them.
Any infomation of this matter is greatly appreciated, thankyou!
Yes, this is possible.
Some high level scenario for a merchant store with beacon.
1) app client needs to have uuid or major id of beacons to be stored locally.
2) merchant store with same uuid or major id will broadcast messages.
3) phone OS keeps listening those messages when entered into geofence, OS will pass on these messages to the apps who are registered for beacons listening.
4) your app will match the uuid embed in the message and identify if its meant for it.
5) if message uuid does not match with uuid on client then app will not consume this message.
6) if message uuid matches then client will consume the message and display it on device, even your app is not running at that point of time.
Related
So I am making this app right now on android basically what it does, It scans the area for a Bluetooth device with a sequence of letter's that it starts with but the last four letters constantly change, also you cant connect to this device either. So I just do a scan and look for the device and if it finds it, it shows in my list and then I read the last four letters and convert them into a double. What I want to do is have Bluetooth start as soon as the app loads up and then keep scanning the hole time so I can get the last four numbers as they go up and they go down.
How can I do this?
This can be done if you use advertisement data or scan response data. so your application has to run in central as well as in other peripheral devices. The peripheral devices has to advertise with advertisement data ( with a unique string and variable part). the advertisement data can be read by the central.
Alternatively if you have the possibility to make the advertisement scannable, the advertisement data contains the fixed part (unique number/string) to identify the device and scan response data can be used to get the required number. note that the advertisement data and scan response data need to be set by custom application.
Q. What are your best practices in managing bluetooth connectivity?
I've read the android bluetooth guide & many bluetooth connectivity tutorials. Not helpful with encapsulation-design nor best practices.
When should I open/close the connection?
Is the "connection" with a single bluetooth device called a "socket" connection?
Can a single connection send data while listening? (...or between listening states).
I've never coded connectivity with external devices before. It took two weeks for me to wrap my head around the code that scans for near-by bluetooth devices and throw them into a ListView. Listeners, Broadcasts, and Adapters!
My project will be printing 1-40 receipts every 15 minutes on a bluetooth receipt printer. At the moment, security is not an issue. On the same connection, it will also be receiving data (sending & receiving simultaneously does not appear to be necessary but would be useful). I'm not yet sure how the devices are configured on this single dongle device but I would guess the devices are connected via USB controller to the dongle.
So far, I have 1 object to manage a single I/O connection. Staticly I open an activity to select a connection (to later save the label, mac, and pin in the database). Based on tutorials, I have "open", "listen", "send", and "close" methods. What confuses me is "how" to use these functions. Can I leave a connection open all day (10hrs) and use it every 3mins? Should I open/close the connection when sending or requesting data? Where would I detect the need to reconnect?
sorry for the short answer, but from my practice with the Bluetooth API, I have found that this video describe the things very good (totally personal opinion...)
Video 1
In addition this is useful when you do NOT have any previous experience
Tutorial
And as last check out this question in stackoverflow it has a bunch of good references and examples!!
Again sorry for the shortage, but I believe that if you check these out at least most of your questions and concerns will become answered!
:)
EDIT
So, let me be a bit more descriptive and share some of my experience.
I have written an App that communicates with BLE device that has 3 functions
double sided event driven button (push the button on phone -> event is fired to the device; push the button on the BLE device -> event is fired to the phone)
send request from phone -> BLE device answers with current battery percentage
continuously reading strength signal (as aprox. distance) between the phone and the BLE device
So far so good, now the things is that the basic approach is:
Search for BLE devices (bluetooth search or "discovery" of nearby bluetooth devices)
Here you will need android permissions!
Choose the device you want to connect to
To differ the devices (maybe there are a lot around you :) ) you can use BLE device's name or UUID or ... best - use the name ;)
After both devices connect to each other you can then start the Gatt communication. The approach with state machine is a little too much overkill for me. But anyway the communication is done through bytes (in my case...)
In one of the videos/resources there was something specific and VERY HELPFUL at least for me! To be honest I don't remember it exactly, but the idea was that before any communication it's RECOMMENDED to read/get all the options from the BLE device or something similar...
Maybe it was something like discoverOptions() or something like that
Great thing will be to know your device "communication codes" or at least I call them that way.
Check this link for example: Link
** Now you can see there are tables with the USEFUL INFO! E.g. if you want to read the battery level you navigate to this page and find that in order to read the battery, the service name is UUID XXXXX and you need to send 0x01 to the BLE device and it will "answer" to your call with some data which is again in bytes.
I really hope that this is somehow helpful!
PLEASE NOTE
This is strictly coming from my experience and there could be some mismatches or wrong terms, but that's how I personally see the things and because my project was long ago, I don't remember most of the things exactly.
IMPORTANT:
This is only a summery of STUCI's provided links above. He has since updated his answer and I have not updated/edited this summery. Topics in my summery are not explanatory but provided for reference and help in generating specific questions.
Original Post...
Thank you Stuci! Some of that was helpful:- some not. I thought it best to collect my thoughts and see what has been explained and if anything hasn't.
(I can't post this much in a comment tho, sorry)
PLEASE CALL ME ON ANYTHING THAT IS INCORRECT.
Video of Bluetooth LE
(Covers a bunch of random things)
While I "dont-like" videos of code:- I watched it because it was recommended ... and I am glad I did. While not very helpful it did introduce some concepts I was unaware of. Since I am targeting old android devices (v8+) the LE features are inconsequential.
Pushing Data: [Depending on the source feature-set], one does not need to continually pull data (ex. with a temperature sensor) but some devices can "push" it to the device on change. Seems to use the 'advertisement" design concept.
UUIDs define Services and/or Characteristics of the connected device.
Possibility to write configuration on (to) connected devices.
Characteristics which seem to be simply "settings" that can be assigned over bluetooth. Not sure if this (~19mins) applies to non-gatt connectoins but seems similar to the state-machine that controls
Advertisements which seem to be the "metadata" regarding the devices current state or config (~24mins). Again, not sure if this even applies to non LE Bluetooth.
Leaving Connections Open
Bluetooth connections can indeed remain open; starting at the point which the "startActivityForResult(...) method is successfully called.
Two basic things affect whether or not one would want to maintain an open connection:
Understand the power consumption.
Having the adapter active simply consumes additional power. If one can keep the adapter shut-off while it is not "absolutely-needed" will mearly save battery power.
Accidental disconnects are managed.
Other than leaving the connection continually connected, one could disconnect & reconnect regularly at specified intervals to ensure a connection is up.
In the thread(s) used for I/O, one could check for a disconnect and reconnect (possibly starting a new thread).
I/O Streams pr Connection
A single connection can indeed "have" simultaneous Input & Output streams. I
Since it was suggested, I re-read Android's Bluetooth Guide and under "managing a connection" (talking about a single socket) I noticed this...
Get the InputStream and OutputStream that handle transmissions through the socket, via getInputStream() and getOutputStream(), respectively.
Read and write data to the streams with read(byte[]) and write(byte[]).
...but continues with noting that read & write block each other. Something I still need to look further into. It seems like you cant I/O simultaneously on the same socket???
Max Connections
I also looked into the max connection issue Stuci added and found no documentation on the Android-side. It might exist, I cant find it. However, most people seem to agree that there is a limitation (that could be as low as 4) imposed by whatever hardware you are coding for.
Some notable links:
- How many devices we can pair via Bluetooth of BLE to Android?
- How many maximum device can we pair via Bluetooth to android device at a time?
- https://groups.google.com/forum/#!topic/android-developers/adeBD275u30
1) i would like to implement dynamic text feature in my server side (java - using GCM) - that mean that i need to custom the push body data to every device but i still want to push to multiple devices at one time.
(using multicastResult = sender.send(mess, devicePushTokenList, 3);
any body knows a way to do it in derver side? (i know a way to do it in the device time before the push arrives)
2) i know apple has a feedback service that i can run in any given time + the feedback of the push response. does GCM has this service too?
thanks!
If you want to use multicast messaging, you will unfortunately need to send the same message.
One solution (which I don't really like) would be to have your app request data from your server upon receiving the message and updating the message appropriately.
You're better off sending messages to each device individually.
As the other answer stated, multicast requires all the messages to be identical.
GCM doesn't have a Feedback Service, and it doesn't need to have one, since it returns an immediate response for each pushed message, and one of the error statuses - NotRegistered - covers the case of devices that uninstalled the app (which is what Apple's Feedback Service is for).
My goal: Make my phone control an Arduino which controls servos which will do cool animations.
How do I get to my goal: I use Java to communicate to the Arduino Nano through the yellow pins (visible on the right picture) through serial (RxD/TxD) (RS-232 protocol) which will tell the Arduino how to control the servos or motors.
Problems:
I don't know which one of the pins that does what, like which one that is GND, which one that is TxD or RxD
I don't know how to tell the phone to do things with its yellow pins (which the Arduino will read and understand to control its servos/motors)
[_] I don't know how to listen to the phone's accelerometer through Java - The thing that lets it tell what is down
[_] I don't know how to listen to the phone's light-sensor
[_] I don't know how to listen to the phone's microphone
[_] I don't know how to listen to the phone's camera
[_] = Things I'm just very curious about that I will use for future projects.
Extra information: I got NetBeans IDE 7.1.1, and I got an Arduino Nano, I got the phone shown above which is called "J10i2 Elm Sony Ericsson".
So I guess what I'm really looking for is someone who knows how to control a phone 100% through Java. Or being pointed in the right direction is also nice!
If you think that I can do this in a better/simpler/smarter way then feel free to leave a comment stating why and how it is better ;)
I would suggest one easy solution, use a REST web service (SOA arquitechture) to solve this problem i did it in my personal case and now im able to control and monitor my house :)
You could simply create a database table representation of your arduino's pins...then just create a service that receives some parameters (i.e> pin no, status -> 1/0, arduino id, etc) and saves them in the database, with your mobile app you could just use the same web service for changing the values.
Finally write down an Arduino app that keeps reading statuses from that service and database (of course using another endpoint/ method in which case you just need to pass your arduino id and it will return a response of all of the different pin status so you can read/process them from your arduino (for example since JSON library is heavy and slow on arduino im passing my return values back from the server to the arduino using simple CSV values i.e> "[pin:status,.....]" i have some code for making HTTP/GET/POST on Arduino you just need the ethernet shield , i could bring you the code if you are interested
i want to send a SMS using GPRS in MIDlet...
anyone can help me??
Thanks in advance...
Sending SMS is a HUGE beast to conquer. Now I don't know the first thing about j2me, but I do know a bit about SMS since I was at one point working on a similar project (abandoned for the reason below).
The short end of it is that you MUST use a GSM carrier to send SMS if you don't know what carrier to send to. This is because carriers know how to send the message to the appropriate cell phone.
You could send via email 5554441234#carrierdomain.com but the problem comes with the fact that you have to know which carrier the phone number points to.
Once upon a time you could tell the carrier by the second set of three digits xxxYYYxxxx (the y's), but you can no longer do this because of phone number portability.
In short, check out Kannel, but you'll still need to send via GSM (you can get PCI cards that hold SIM cards), or you can pay a subscription.