Develop Reference

Is it possible to android to lost part of a command writen to a characteristic via BlueTooth via BLE?

I'm developing an adaptation for an android app, to communicate with a remote control, which has some pre defined commands.
I've followed this implementation to do the Bluetooth communication and it's working fine for sometime.
This app should communicate with the remote control every 5 minutes or less, and I've been using the app for almost 6 months now. The last week I've some command clashes problem and looking at the logs I couldn't identify why did that happened. The last time that this had happened the app was running for more than 24h, communicating with the remote control, without any communication issue.
Two of it's commands have some similar characters, the first one that have to be done, to establish the connection.
OK_CONN
And an sniffer command which keeps the pilot awake listening for some sensor data:
N
Looking at the logs I can see the answer for command N, after applying the command OK_CONN.
Is it possible for a Bluetooth command to lost part of it's data, during an established communication or am I doing something wrong when writing to a characteristic? Should I change the command names to avoid this kind of clash?
I'm using android 9, at a Sony XPeria XZ phone.
Edit to clarify #Emil comment
07:02:12.880 [BleThread] writing <OK+CONN> to characteristic
07:02:12.368 [Binder:19249_F] [onCharacteristicChanged():274]:
n command confirme
Looking at the logs I see that the last written command as an ok_conn but it has written only the N, this is been show as the last line, it has confirmed to receive the n command alone, instead of receiving the full data of ok_conn.
By name clashes I mean that maybe the last N of the ok_conn command is been accepted as the command.
I just realized what's going on, you can post that as an answer #Emil, my problem was at the logic that sends the first command, sometimes I send this command and the micro controller is not started yet, that's probably the reason of it getting only part of the command.

Not sure what you mean by name clashes, but Android will always write what you told it to write, without packet loss, as long as you follow the rules to never have more than one outstanding operation (always wait for callback before you send the next operation) and that your data must fit within the maximum length for the corresponding operation.

Where does 'baud rate' value go in serial Android-2-Arduino communication over USB

Issues with Android-2-Arduino communication made it clear to me I have no clue which parts of the chain are (directly) affected by the baud rate. Could you please confirm/correct following assumptions?
The 'baud rate' value is not related to anything on the Android side. Therefore it is not a bug when an Android USB/Serial library only sends the baud rate value (9600, 125000, etc.) to the other side via controlTransfer, not storing it anywhere, not setting it somehow to the Android device itself.
When calling usbConn.controlTransfer with 'baud rate' parameter on Android, this command is NOT redundant to me calling Serial.init(baudRate) in the Arduino code. Both these calls are intended for different HW/parts. Both of those parts reside on Arduino. (Both, obviously, must be called with identical value.)

HID two ways communication between Arduino and Android (controlTransfert)

I want to have a 2 two way (in and out) HID communication between a leonardo and an Android tablet (acting as a host). On the leonardo, I use Nicohood HID project
I have successfully managed to make the code work on Linux, Windows and MacOs, so it is possible.
Using a pure android implementation, I can only receive data from the leonardo but not send to it...
From what I have seen in the descriptor, the data are sent from the device (IN direction) using a specific endpoint. For the other way (OUT, to the device), we must use the control endpoint.
Nevertheless, it doesn't work on android. Here is the code I used :
UsbDeviceConnection mUsbConnection = mUsbManager.openDevice(myDevice);
byte data[] = {7, 11, 13, 17};
int resOut = mUsbConnection.controlTransfer(0x21, 9, 200, 2, data, data.length, 50);
// => resOut value is always -1 (didn't succeed to communicate)
For the parameters, I used the answers to this question: Using Android to Communicate with a USB HID Device and looked at libusb / nicohood hid communication examples on linux...
Out of luck, I tried to change the value from "200" to "0" or the index from 0 to 1 or 2, but I don't really know what they mean, and it didn't really help...
How can I send data to the device using the control endpoint with android ?
PS : I can read HID messages from the device, so it is not a permission issue.

Android communicating to HFP device via AT commands

im trying to control a bluetooth bracelet with vibration function via HFP (hands free profile) in Android. I've been able to connect to the bracelet and access the input- and outputstream.
My goal is to simulate an incoming call so that the bluetooth bracelet starts vibrating (which seems to be the only way to do that). To do this, im using AT commands. In the bluetooth specs at https://www.bluetooth.org/docman/handlers/downloaddoc.ashx?doc_id=238193 on page 22 you can see the handshake to establish service level connection.
I need to establish this connection to use the "+CIEV" command (see handshake page 48).
But when my bracelet returns the command "AT+CIND=?" I dont know how to respond. I can't find any hints on how to answer with the "CIND:" command. Also I dont know how to send the acknowledgement (is it just "OK"?).
That might even be the completely wrong way to do this. Every suggestion is appreciated. I only found one post on stackoverflow that helped me in some way, rest of the posts I found were unanswered.
By the way, im using a smartphone with Android 4.1.2. The bracelet supports HFP and HSP. Thanks in advance.
UPDATE 10/29/2014
===== Connection through RFCOMM Socket established at this point =====
// read AT+BRSF=0 from device
byte[] buffer = new byte[200];
mBluetoothSocket.getInputStream().read(buffer);
Log.d(TAG, new String(buffer).trim());
//write answer BRSF: ...
mBluetoothSocket.getOutputStream().write("+BRSF=20\r".getBytes());
mBluetoothSocket.getOutputStream().write("OK\r".getBytes());
// read AT+CIND=? command
buffer = new byte[200];
mBluetoothSocket.getInputStream().read(buffer);
Log.d(TAG, new String(buffer).trim());
//write answer CIND: ...
mBluetoothSocket.getOutputStream().write("+CIND: (\"battchg\",(0-5)),(\"signal\",(0-5)),
(\"service\",(0,1)),(\"call\",(0,1)),(\"callsetup\",(0-3)),
(\"callheld\",(0-2)),(\"roam\",(0,1))".getBytes());
mBluetoothSocket.getOutputStream().write("OK".getBytes());
// read AT+CIND?
buffer = new byte[200];
mBluetoothSocket.getInputStream().read(buffer);
Log.d(TAG, new String(buffer).trim());
Following the procedure of the protocol, I should receive the "AT+CIND?" command and then I could send the command "+CIND: 5,5,1,0,0,0,0", but...I dont receive the "AT+CIND?" command. Actually im not receiving anything. Am I missing something? Sending an "OK" doesnt change anything btw...

I was fiddeling with exaclty the same problem. After days of trial and error, I finally got it to work.
I think it depends on the speed at wich you answer the HF's commands, as well as on the correct line-endings ("COMMAND").
Here is my DroidScript which works. It's not cleaned up, but it works.
https://gist.github.com/t-oster/68a568ac4c4e133f67ac

Also, the one example I found that seemed to almost work, it's expecting the responses to be top and tailed with crlf:
"\r\n+BRSF=20\r\n"
"\r\nOK\r\n"
Still struggling with the rest of it myself.

refer to bluetooth hfp 1.5 spec in which you can understand CIEV response
normally when not in any call setup, response can be +CIND = 1,0,0,0,5,0,5
Note these values are based on the hfp spec, on incoming call return +CIEV: ,
ind- indicator for callsetup and value as 1 and then RING commands to the bracelet

Android Development Usb Transfer

I am fairly new to Android Development and i have recently been exploring Usb Host.
Would anyone be able to tell me how to use Bulk Transfer so that i can see what an external camera sees but instead show it on my tablet?
Camera : Canon Powershot A1300
Tablet : Iconia A200
I have looked around stack overflow and some other forums but have not yet been able to find a good explanation on how to use Bulk Transfer or what constants to use as parameters for retrieving certain data.
I am able to see the endpoints and set up a connection with the external camera but I do not know where to go from here.
Any help is deeply appreciated.

The USB Host APIs in Android are fairly thin, by which I mean once you have gone beyond enumerating the interfaces/endpoints and creating a connection it doesn't do much more to assist you. You are then in the realm of communicating with raw USB data transfers, the format of which depend on the device class your camera represents. Your request is somewhat a can of worms, so I will do my best to provide helpful resources.
Unfortunately, storage and media devices are not the simplest device classes to interpret, so it may be difficult if you are just getting your feet wet on USB in general. The best advice I can give is to take a look at the device class specs for the interface class your camera reports (most are either Mass Storage or MTP), which can be found here: http://www.usb.org/developers/devclass_docs
The spec document will enumerate the commands you need to use to communicate with the device. I would also recommend checking out USB In a Nutshell, which does a great job of pointing out how USB requests are constructed in general, which can help you map what you see in a the spec docs to the parameters found in the methods of UsbDeviceConnection: http://www.beyondlogic.org/usbnutshell/usb1.shtml
There will likely be a handful of control commands you need to send to "endpoint 0" initially to set up the camera, and then the remaining transfers will likely take place over the bulk endpoints.
In Android terms, control requests can only be sent synchronously using UsbDeviceConnection.controlTransfer(), meaning this method blocks until the transfer is complete. The parameters that fill in this method are found in the spec docs for your device class.
Requests on bulk endpoints can be sent synchronously via UsbDeviceConnection.bulkTransfer() OR asynchronously using a UsbRequest instance. With UsbRequest you can queue a transfer and then later check back (via UsbDeviceConnection.requestWait()) for the results.
I have some examples on my Github page in using the host APIs to do some basic interrupt and control transfers to get information like device descriptors. Perhaps some of that will be helpful to you as well: https://github.com/devunwired/accessory-samples
With regards to your question about the USB example code:
The request made in this code is just a generic "Get Configuration Descriptor" request that all USB devices must respond to (it's a core command, not class-specific). In fact, its the request where the Android APIs get the information you can query for interfaces and endpoints. The field values come from the Core USB Specification (this command specifically is defined at section 9.4.3 and 9.6.3 in the 3.0 spec): http://www.usb.org/developers/docs/ or a more helpful description you can find from USB in a Nutshell, which has a little more discussion: http://www.beyondlogic.org/usbnutshell/usb5.shtml#ConfigurationDescriptors
The length is somewhat arbitrary, this tells the driver how many bytes to read or write. Most USB host drivers will first query the device descriptor, which includes a field telling the host the Max Packet Size the device supports, and then will use that size as the length for future requests. A full-featured driver would probably make this command and then check the length bytes first (the wTotalLength field of the descriptor) to see if the buffer was large enough, and modify/resend if not. In the example, I just chose 64 for simplicity because that is the "maximum" Max Packet Size the protocol defines as supportable.
Again, then making requests of the specific data your device has to offer, those commands will be found in the specific class document, not the core specification.