Develop Reference

Receiving Bluetooth Low Energy Data Via Android App

The project I am currently working on involves a weight scale that has built-in BLE and my smartphone. The scale connects to the smartphone via BLE to send the current weight data to its app (I assume this is prioritized.) Although I can't figure out how to get the correct UUID to communicate with the scale in my own Android App as it doesn't seem to be using the standard GATT Services. The devices seem to use 0x2901, 0x2902...0x290X
Scale model: HNY200 (Color Black)
Link to scale: https://www.healthometernuyu.com/nuyu-products/scales/wireless-scale/HNY200KD.html
After using a BLE scanner on my phone I was able to determine the BLE Name for the device (Much like the SSID in a network) and the MAC Address. However, it also shows a long list of CUSTOM SERVICE and CUSTOM CHARACTERISTIC options each with Descriptors and their properties such as read and write. I would assume the data im searching for (The weight value) would come packaged in a CUSTOM CHARACTERISTIC with the properties including READ. After analyzing each individual one the value is either the exact same hexadecimal number each time or has no value at all. The ones with no value instead have "OTA_STATUS", "OTA_CMD", or "OTA_DATA" but does not reveal anything besides that.
BLE Scan of the device looking at the most interesting characteristics (but not all):
https://imgur.com/a/iHWDoSM
I currently dont have any code for the android app as I am just following along with the Android Developers Tutorial. However, in previous research, It seems as though I will need the correct UUID's as I might have to reverse engineer the protocol the scale is using to send prioritized data to its app. Some BLE scanners work to find the scale and some do not.
I expected one characteristic to reveal a value of the weight being displayed on the scale and instead I got very large hex values, nothing at all, or some string value such as "OTA_DATA".

Get BLE Scan without filter duplicate UUID

I'm writing an BLE application, where need to track if peripherals device is advertising or has stop.
I followed getting peripherals without duplications this and BLE Filtering behaviour of startLeScan() and I completely agree over here.
To make it feasible I kept timer which re-scan for peripherals after certain time (3 sec). But with new device available on market(with 5.0 update), some time re-scan take bit time to find peripherals.
Any suggestion or if anyone have achieved this?

Sounds like you're interested in scanning advertisements rather than connecting to devices. This is the "observer" role in Bluetooth Low Evergy, and corresponds to the "broadcaster" role more commonly known as a Beacon. (Bluetooth Core 4.1 Vol 1 Part A Section 6.2)
Typically you enable passive scanning, looking for ADV_IND packets broadcast by beacons. These may or may not contain a UUID. Alternatively, you can active scan by transmitting SCAN_REQ to which you may receive a SCAN_RSP. Many devices use different advertising content in ADV_IND and SCAN_RSP to increase the amount of information that can be broadcast - you could, for instance, fit a UUID128 into the ADV_IND followed by the Device Name in the SCAN_RSP. (Bluetooth Core 4.1 Vol 2 Part E Section 7.8.10)
Now you need to define "go away" - are you expecting the advertisements to stop or to fade away? You will get a Receive Signal Strength Indication "RSSI" with each advertisement (Bluetooth Core 4.1 Vol 2 Part E Section 7.7.65.2) - this is how iBeacon positioning works and there's plenty of support for beacon receivers in Android.
Alternatively you wait for N seconds for an advertisement that should be transmitted every T seconds where N>2T. The downside of the timed approach is that probably not receiving a beacon isn't the same as definitely receiving a weak beacon; to be sure you need N to be large and that impacts the latency between the broadcaster being switched off or moving out of range and your app detecting it.
One more thing - watch out that Advertising stops if something connects to a Peripheral (if you really are scanning for peripherals) another good reason to monitor RSSI.

First scenario: Bonded Devices
We know that if a bond is made, then most of the commercially available devices send directed advertisements in during re-connection. In situations such as this, according to BLE 4.0 specification, you cannot scan these devices on any BLE sniffer.
Second scenario: Connectable Devices
Peripheral devices are usually in this mode when they are initially in the reset phase. The central sends a connect initiator in response to an advertisement packet. This scenario offers you a lot of flexibility since you can play around with two predominant configuration options to alter connection time. These are: slavelatency on the peripheral and conninterval on the central. Now, I don't know how much effort it's going to take get it working on the Android platform, but if you use the Bluez BLE stack and a configurable peripheral such as a TI Sensor tag, then you can play around with these values.
Third scenario: Beacon devices
Since this is what your question revolves around, according to the BLE architecture, there are no parameters to play with. In this scenario, the central is just a dumb device left at the mercy of when a peripheral chooses to send it's beaconing signal.
Reference:
http://www.amazon.com/Inside-Bluetooth-Communications-Sensing-Library/dp/1608075796/ref=pd_bxgy_14_img_z
http://www.amazon.com/Bluetooth-Low-Energy-Developers-Handbook/dp/013288836X/ref=pd_bxgy_14_img_y

Edit: I forgot, have you tried setting the advertiser to non-connectable? That way you should be able to get duplicate scan results
I am dealing with a similar issue, that is, reliably track the RSSI values of multiple advertising devices over time.
It is sad, the most reliable way i found is not nice, rather dirty and battery consuming. It seems due to the number of android devices that handle BLE differently the most reliable.
I start LE scan, as soon as i get a callback i set a flag to stop and start scan again. That way you work around that DUPLICATE_PACKET filter issue since it resets whenever you start a fresh scan.
The ScanResults i dump into a sqlite db wich i shrink and evaluate once every x seconds.
It should be easy to adapt the shrinking to your use case, i.e. removing entries that are older than X, and then query for existance of a device to find out if you received a ScanResult in the last X seconds. However dont put that X value too low, as you must take into account that you still lose alot of advertisement packets on android LE scan, compared to a BLE scan on i.e. bluez..
Edit:
I can add some information i already found for speeding up the performance on Advertisement discovery. It involves modifying and compiling the bluedroid sources and root access to the device. Easiest would be building a full android yourself, i.e. Cyanogenmod.
When a LE scan is running, the bluetooth module sends the scan sesponse via HCI to the bluedroid stack. There various checks are done until it finally gets handed to the Java onScanResult(...) which is accessed via JNI.
By comparing the log of the hci data sent from the bluetooth module (can be enabled in /etc/bluetooth/bt_stack.conf) with debug output in the bluedroid stack aswell as the Java side i noticed that alot of advertisement packets are discarded, especially in some check. i dont really understand, beside that it has something to do with the bluedroid inquiry database
From the documentation of ScanResult we see that the ScanRecord includes the advertisement data plus the scan response data. So it might be that android blocks the report until it got the scan response data/ until it is clear there is no scan response data. This i could not verify, however a possibility.
As i am only interested in rapid updates on the RSSI of those packets, i simply commented that check out. It seems that way every single packet i get from the bluetooth moduly by hci is handed through to the Java side.
In file btm_ble_gap.c in function BOOLEAN btm_ble_update_inq_result(tINQ_DB_ENT *p_i, UINT8 addr_type, UINT8 evt_type, UINT8 *p)
comment out to_report = FALSE; in the following check starting on line 2265.
/* active scan, always wait until get scan_rsp to report the result */
if ((btm_cb.ble_ctr_cb.inq_var.scan_type == BTM_BLE_SCAN_MODE_ACTI &&
(evt_type == BTM_BLE_CONNECT_EVT || evt_type == BTM_BLE_DISCOVER_EVT)))
{
BTM_TRACE_DEBUG("btm_ble_update_inq_result scan_rsp=false, to_report=false,\
scan_type_active=%d", btm_cb.ble_ctr_cb.inq_var.scan_type);
p_i->scan_rsp = FALSE;
// to_report = FALSE; // to_report is initialized as TRUE, so we basically leave it to report it anyways.
}
else
p_i->scan_rsp = TRUE;

Detecting whether a BLE device is connectable on Android

I am working on a project for configuring beacons. A certain amount of time after being powered on, a beacon becomes unconfigurable until it is power-cycled. In order to show a list of the configurable beacons, I am looking at certain characteristics (Bluetooth device name, certain manufacturer data in the advertising packet). I also need to know if it is "connectable", i. e. if the PDU Type in the BLE advertising packet for the device indicates that it is connectable. I've searched the Android Bluetooth classes high and low, both in Android 4.X and 5.X and haven't been able to find anything that will tell me this information.
I realize that one way to determine the beacon connectability is to connect up to it, e. g.: device.connectGatt(...). However, I've seen it take over two minutes sometimes before a callback to onConnectionStateChange comes back with STATE_DISCONNECTED. Also, there may be many of these beacons in an environment, and connecting up to every single one that might be configurable would be inefficient.
The iOS equivalent of this attribute can be found in the advertisementData dictionary under the key CBAdvertisementDataIsConnectable in the CBCentralManagerDelegate callback method centralManager:didDiscoverPeripheral:advertisementData:RSSI.
So, the question is: is there a way on Android to determine whether or not a BLE device is "connectable" from advertising data or scan result or ... ?

UPDATE: AS of the finalized APIs in the Android O SDK, the ScanResult class (itself added as of Android 5.0) now has the isConnectable() method. Detecting connectable advertisements is possible only on Android 8.0+. See here for more info: https://developer.android.com/reference/android/bluetooth/le/ScanResult.html#isConnectable()
Prior to Android 8.0, unfortunately it is not possible.
A connectable advertisement is determined by the PDU Header byte 0. You can see this in the example structure below:
d6 be 89 8e # Access address for advertising data (this is always the same fixed value)
40 # Advertising Channel PDU Header byte 0. Contains: (type = 0), (tx add = 1), (rx add = 0)
24 # Advertising Channel PDU Header byte 1. Contains: (length = total bytes of the advertising payload + 6 bytes for the BLE mac address.)
05 a2 17 6e 3d 71 # Bluetooth Mac
The problem is on devices prior to Anroid 8.0, the Android scanning APIs give you no access to these headers. You get exactly three fields in the callback from Android 4.x:
onLeScan(BluetoothDevice device, rssi, byte[] scan data)
The scan data byte array starts after the header bytes mentioned above. And from what I can see of the BluetoothDevice definition, none of the fields or methods tell you if it is a connectable advertisement -- the class is just a container for the bluetooth mac address with methods to exercise functions on the bluetooth stack. And there are no methods in IBluetooth.aidl which is the private interface to the bluetooth stack (and what BluetoothDevice calls to get its info) that can get this flag.
It appears that this information is not passed up to the Java layer from the BlueDroid stack prior to Android 8.0.

It should be possible since Nordic's nRF Master Control Panel does this.
After some digging I think I know how it does this. I'm not sure it's the right way to do it though.
I tried using the LE Advertiser and setting the device as connectable. In the Nordic app, a device is set as connectable depending on the bytes found at scanResult.getFlags().
I found that this code works for my devices:
int flags = scanResult.getScanRecord().getAdvertiseFlags();
if ((flags & 2) == 2) {
//connectable
}

Use Find Me Profile in Android 4.3

I a trying to understand and modify the BLE sample von Android.com, now I can discover my sample BLE Device (HTC Fetch) and now I want to understand all that GATT and BLE stuff.
What are Characteristics and what are Profile and what are Serivces and what do they mean in the Bluetooth Low Energy World? I used HTC Dev and found a Service and a Characteristics UUID.
https://www.htcdev.com/devcenter/opensense-sdk/bluetooth-smart/htc-fetch/
But I guess what I need is the Find Me Profile, cause for the first steps I only want to get the Find Me react to a Button click.
https://developer.bluetooth.org/gatt/profiles/Pages/ProfileViewer.aspx?u=org.bluetooth.profile.find_me.xml
How to implement this in my App?
When I understand everything I try Power and Proximity (reading RSSI and compare with defined range).
Can some one help me understanding Bluetooth LE?

Here's a related post
How to use the profile of PROXIMITY PROFILE,IMMEDIATE ALERT SERVICE and Find Me Profile in android 4.3 BLE?
Basically you can approximate a proximity level using tx+power - rssi or distance roughly with
d = (rssi-A)/-20 (where A = rssi at one meter) or simply use rssi mapping out ranges to display You could also initially base it on just the connection range and skip rssi.
As for the FindMe, simply write the low or high alert values to make it sound when you press a button in your app. For pressing a button on the device use the UUIDs shown in the documentation.
sample code for that device is forthcoming

ADK blink tutorial: on board LED is always on

I have a Duemilanove and ADK and I followed this and with the exception of some SDK updates, I followed it exactly.
Problem: the onboard LED doesn't blink but is always on.
Issues:
byte array is being successfully sent to the ADK from the phone, verified by monitoring serial port of arduino board
High & low signal is being properly handled in the arduino code (same verification).
the blink tutorial without the ADK blinks the on board LED properly.
So, what is wrong? Is it possible that the ADK board is always sending a HIGH signal to the on board LED and I need to use an 'external' LED for testing? A lot of the tutorials I've seen do this so could that be why?

Try to write a small blink program, just to check that everything is alright in your ADK board.

The onboard Arduino LED is on initially. It looks like it is never being turned off.
In the linked instructions, under the section How To Receive Data From The Android Device , the first line of the loop() function is:
byte msg[0];
Then to receieve data in the call to AndroidAccessory.read() the value sizeof(msg) is used to determine how many bytes to read.
However, because msg was defined to be 0 bytes long, no bytes will be read, len will be zero and the LED will not be updated.
Instead, try changing the line to:
byte msg[1];

I haven't used the shield you are using but it looks like it uses SPI for communication. SPI uses pin 13 for the serial clock signal (SCK). Given this I would expect the SCK signal may be interfering with you trying to control the LED.
I would suggest trying to wire an LED to a different digital pin such as pin 8 and update the Arduino sketch to use pin 8. This would remove the possibility of conflict.