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I have bluetooth shield serial comms up and running no problem. I am now trying to add an RFID reader which has a serial connection to the Arduino UNO. As soon as I open the RFIDSerial connection the Bluetooth connection stops working. I thought that SoftwareSerial supported several simultaneous serial connections? Any help greatly appreciated.
(Redirected from Bluetooth protocols)
The wireless data exchange standard Bluetooth uses a variety of protocols. Core protocols are defined by the trade organization Bluetooth SIG. Additional protocols have been adopted from other standards bodies. This article gives an overview of the core protocols and those adopted protocols that are widely used.
Nov 21, 2015 I'm having this same problem with two computers I have just upgraded to win 10. I have an app on win phone 8.1 (Nokia Lumia 925) that worked ok with win8.1 but now won't work with either computer running win 10 home or win 10 pro. Its a simple terminal app that uses the serial port to control my desktop apps. (It sends basic strings.). Download this app from Microsoft Store for Windows 10, Windows 8.1, Windows 10 Mobile, Windows Phone 8.1. See screenshots, read the latest customer reviews, and compare ratings for Bluetooth Serial Terminal.
The Bluetooth protocol stack is split in two parts: a 'controller stack' containing the timing critical radio interface, and a 'host stack' dealing with high level data. The controller stack is generally implemented in a low cost silicon device containing the Bluetooth radio and a microprocessor. The host stack is generally implemented as part of an operating system, or as an installable package on top of an operating system. For integrated devices such as Bluetooth headsets, the host stack and controller stack can be run on the same microprocessor to reduce mass production costs; this is known as a hostless system.
Controller stack[edit]
Asynchronous Connection-Less [logical transport] (ACL)[edit]
The normal type of radio link used for general data packets using a polling TDMA scheme to arbitrate access. It can carry packets of several types, which are distinguished by:
- length (1, 3, or 5 time slots depending on required payload size)
- Forward error correction (optionally reducing the data rate in favour of reliability)
- modulation (Enhanced Data Rate packets allow up to triple data rate by using a different RF modulation for the payload)
A connection must be explicitly set up and accepted between two devices before packets can be transferred.
ACL packets are retransmitted automatically if unacknowledged, allowing for correction of a radio link that is subject to interference. For isochronous data, the number of retransmissions can be limited by a flush timeout; but without using L2PLAY retransmission and flow control mode or EL2CAP, a higher layer must handle the packet loss.
ACL links are disconnected if there is nothing received for the supervision timeout period; the default timeout is 20 seconds, but this may be modified by the master.
Synchronous Connection-Oriented (SCO) link[edit]
The type of radio link used for voice data. An SCO link is a set of reserved time slots on an existing ACL link. Each device transmits encoded voice data in the reserved timeslot. There are no retransmissions, but forward error correction can be optionally applied. SCO packets may be sent every 1, 2, or 3 time slots.
Enhanced SCO (eSCO) links allow greater flexibility in setting up links: they may use retransmissions to achieve reliability, allow for a wider variety of packet types and for greater intervals between packets than SCO, thus increasing radio availability for other links(.)
Link Management Protocol (LMP)[edit]
Used for control of the radio link between two devices, handling matters such as link establishment, querying device abilities and power control. Implemented on the controller.
Host Controller Interface (HCI)[edit]
Standardized communication between the host stack (e.g., a PC or mobile phone OS) and the controller (the Bluetooth integrated circuit (IC)). This standard allows the host stack or controller IC to be swapped with minimal adaptation.
There are several HCI transport layer standards, each using a different hardware interface to transfer the same command, event and data packets. The most commonly used are USB (in PCs) and UART (in mobile phones and PDAs).
In Bluetooth devices with simple functionality (e.g., headsets), the host stack and controller can be implemented on the same microprocessor. In this case the HCI is optional, although often implemented as an internal software interface.
Low Energy Link Layer (LE LL)[edit]
This is the LMP equivalent for Bluetooth Low Energy (LE), but is simpler. It is implemented on the controller and manages advertisement, scanning, connection and security from a low-level, close to the hardware point of view from Bluetooth perspective.
Host stack[edit]
Logical link control and adaptation protocol (L2CAP)[edit]
Bluetooth Serial App
L2CAP is used within the Bluetooth protocol stack. It passes packets to either the Host Controller Interface (HCI) or, on a hostless system, directly to the Link Manager/ACL link.
L2CAP's functions include:
- Multiplexing data between different higher layer protocols.
- Segmentation and reassembly of packets.
- Providing one-way transmission management of multicast data to a group of other Bluetooth devices.
- Quality of service (QoS) management for higher layer protocols.
L2CAP is used to communicate over the host ACL link. Its connection is established after the ACL link has been set up.
In basic mode, L2CAP provides packets with a payload configurable up to 64 kB, with 672 bytes as the default MTU, and 48 bytes as the minimum mandatory supported MTU. In retransmission and flow control modes, L2CAP can be configured for reliable or asynchronous data per channel by performing retransmissions and CRC checks. Reliability in either of these modes is optionally and/or additionally guaranteed by the lower layer Bluetooth BDR/EDR air interface by configuring the number of retransmissions and flush timeout (time after which the radio will flush packets). In-order sequencing is guaranteed by the lower layer.
The EL2CAP specification adds an additional enhanced retransmission mode (ERTM) to the core specification, which is an improved version of retransmission and flow control modes. ERTM is required when using an AMP (Alternate MAC/PHY), such as 802.11abgn.
Bluetooth network encapsulation protocol (BNEP)[edit]
BNEP is used for delivering network packets on top of L2CAP. This protocol is used by the personal area networking (PAN) profile. BNEP performs a similar function to Subnetwork Access Protocol (SNAP) in Wireless LAN.
In the protocol stack, BNEP is bound to L2CAP.
Radio frequency communication (RFCOMM)[edit]
![Failure Failure](https://i.stack.imgur.com/gpBRy.jpg)
The Bluetooth protocol RFCOMM is a simple set of transport protocols, made on top of the L2CAP protocol, providing emulated RS-232serial ports (up to sixty simultaneous connections to a Bluetooth device at a time). The protocol is based on the ETSI standard TS 07.10.
RFCOMM is sometimes called serial port emulation. The Bluetooth serial port profile is based on this protocol.
RFCOMM provides a simple reliable data stream to the user, similar to TCP. It is used directly by many telephony related profiles as a carrier for AT commands, as well as being a transport layer for OBEX over Bluetooth.
Many Bluetooth applications use RFCOMM because of its widespread support and publicly available API on most operating systems. Additionally, applications that used a serial port to communicate can be quickly ported to use RFCOMM.
In the protocol stack, RFCOMM is bound to L2CAP.
Service discovery protocol (SDP)[edit]
Used to allow devices to discover what services each other support, and what parameters to use to connect to them. For example, when connecting a mobile phone to a Bluetooth headset, SDP will be used to determine which Bluetooth profiles are supported by the headset (headset profile, hands free profile, advanced audio distribution profile, etc.) and the protocol multiplexer settings needed to connect to each of them. Each service is identified by a Universally Unique Identifier (UUID), with official services (Bluetooth profiles) assigned a short form UUID (16 bits rather than the full 128).
In the protocol stack, SDP is bound to L2CAP.
Telephony control protocol (TCS)[edit]
Also referred to as telephony control protocol specification binary (TCS binary)
Used to set up and control speech and data calls between Bluetooth devices. The protocol is based on the ITU-T standard Q.931, with the provisions of Annex D applied, making only the minimum changes necessary for Bluetooth.
TCS is used by the intercom (ICP) and cordless telephony (CTP) profiles. The telephone control protocol specification is not called TCP, to avoid confusion with transmission control protocol (TCP) used for Internet communication.
Bluetooth Serial Failure Has Occurred Mac
Audio/video control transport protocol (AVCTP)[edit]
Used by the remote control profile to transfer AV/C commands over an L2CAP channel. The music control buttons on a stereo headset use this protocol to control the music player.
In the protocol stack, AVCTP is bound to L2CAP.
Audio/video data transport protocol (AVDTP)[edit]
Used by the advanced audio distribution profile to stream music to stereo headsets over an L2CAP channel. Intended to be used by video distribution profile.
In the protocol stack, AVDTP is bound to L2CAP.
Object exchange (OBEX)[edit]
Object exchange (OBEX; also termed IrOBEX) is a communications protocol that facilitates the exchange of binary objects between devices. It is maintained by the Infrared Data Association but has also been adopted by the Bluetooth Special Interest Group and the SyncML wing of the Open Mobile Alliance (OMA).
In Bluetooth, OBEX is used for many profiles that require simple data exchange (e.g., object push, file transfer, basic imaging, basic printing, phonebook access, etc.).
Low Energy Attribute Protocol (ATT)[edit]
Similar in scope to SDP but specially adapted and simplified for Low Energy Bluetooth. It allows a client to read and/or write certain attributes exposed by the server in a non-complex, low-power friendly manner.
Device Power Failure Bluetooth
In the protocol stack, ATT is bound to L2CAP.
Low Energy Security Manager Protocol (SMP)[edit]
This is used by Bluetooth Low Energy implementations for pairing and transport specific key distribution.
In the protocol stack, SMP is bound to L2CAP.
External links[edit]
Retrieved from 'https://en.wikipedia.org/w/index.php?title=List_of_Bluetooth_protocols&oldid=974771142'
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by Matthew Ford 15th November 2017(originally posted 15th November 2017)
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Thistutorial covers some of the common problems, and their solutions,when using Bluetooth Low Energy devices (BLE) or Bluetooth V4,Bluetooth V5 modules. However “Do you really need to use BLE?”
Ifyou just need some way to connect your Arduino project to your mobileor PC then a much better and easier solution is to use a BluetoothClassic (Bluetooth V2) shield, like IteadBluetooth Shield, OR a cheap WiFi shield like this project,Cheap/SimpleWifi Shield.
Icrosoft word. Youshould only consider using a BLE module if you need one of its uniquefeatures, such as very low power consumption, or you want to stay onthe “bleeding edge” of technology. The RemoteControlled Light switch is an example of a project that needs torun of very low current <1.5mA so that is does not need anadditional power supply.
CustomBLE – No Programming required provides details on more thehalf a dozen different BLE modules.
Thereare a number of problems with using BLE for general purpose control.
- Older mobiles and computers do not support BLE
- The Bluetooth SIG standard does not define a general purpose UART connection.
- Programming BLE control Apps is difficult.
- Programming BLE devices is not straight forward
- Some BLE modules/software stacks deliver the same message twice is quick succession
- Some BLE modules/software stacks drop bytes when sending long messages.
Older mobiles and computers do notsupport BLE
Bluetooth used to be easy to use, every Android andiPhone and most computers supported Bluetooth V2. The BluetoothSerial Port Profile (SPP) was the standard way to get a general dataconnection via Bluetooth and all Arduino Bluetooth V2.0 shieldssupported it.
Note: not all Android mobilessupport BLE. You can check if your mobile supports BLE with the freeNordicnRF Master Control Panel (BLE) android app . If your mobile doesnot support BLE, then pfodApp will not display the +BLE button in theadd/edit connections screen.
The BLE mobile hardware is still being ironed out. Onthe Android side, BLE support was introduced in V4.2 but that versionand V4.3 was very buggy. V4.4 improved the BLE support and laterversion should be better.
The only solution is to update your mobile phone orcomputer to a later one that supports BLE. Note: BLE V5 specificationhas just been release so you may need to update again shortly to useis enhanced features, like Mesh support.
TheBluetooth SIG standard does not define a general purpose UARTconnection.
Thebiggest problem with trying to use BLE for general purpose control isthat the SIG specification does NOT define a standard UARTconnection. Bluetooth V5 specification does not fix this problem.Where as Bluetooth V2 (Bluetooth Classic) defined Bluetooth SerialPort Profile (SPP) which was universal and easy to code, BLE does notdefine a replacement.
Thishas resulted in each manufacture having to define their own 'uart'service and your mobile app needs to know the details in order to useit.
Onesolution is to use a general purpose app, like pfodApp,which recognizes half a dozen or more common 'uart' services fromvarious module manufactures. pfodApp has it own general purposemessaging system, pfod. The pfod messaging system is particularlysuited for BLE because almost all the messages are very short(<20bytes)
NordicSemiconductor has defined their own UART service, which pfodApprecognizes, and which a number of manufactures use. There are appsfrom Nordic Semiconductor to let to test its uart connection, NordicnRF Master Control Panel (BLE) and nRFToolbox for BLE However even for this 'standard' there is someconfusion about the TX versus RX characteristic. pfodApp handles bothalternatives.
ProgrammingBLE control Apps is difficult.
Programmingan Android or IOS app to make a BLE 'uart' connection is non-trivial.There are services and characteristics to be handled and messagingdelays to be allowed for as well as the 20byte message limit of BLEV4.
ThenRFToolbox for BLE provides a simple 'uart' connection if and onlyif the module you are connecting to uses Nordic's uart (correctly).The Android pfodApp onthe other hand provides a general purpose menu and graphical drivencontrol platform for a variety of different modules. The menus andgraphics displayed on pfodApp are completely controlled by the codein your Arduino or BLE module, no Android mobile coding is necessaryto get functional controls.
A Bluetooth Serial Failure Has Occurred
ProgrammingBLE devices is not straight forward.
Becauseof the lack of a BLE uart standard each module manufacture definestheir own, or does not define any at all. This means there is notstandard Arduino library for BLE. Some modules connect via Serial,some via SPI, some via direct library calls.
Thefree pfodDesignerapp provides a solution to this by letting you design pfodAppmenus and then generating the code for a variety of BLE modules. Evenif you don't want to pfodApp, the generated code provides you with atemplate 'uart' connection for you own use.
Some BLE modules/software stacksdeliver the same message twice is quick succession
While testing a number of BLE modules it was foundthat some occasionally deliver the same message from the mobile app,twice in quick succession. That is within about 100mS. Depending ofhow your code and commands are structure this can be a problem.
For example if you use the same command to toggle aswitch on and off then you will find the switch stays OFF when youtry to turn it on because the second delivery of the same commandturns it off as soon as the real command has turned it on. Terminix employee handbook.
pfodAppV3.322+ overcomes this problem by adding a sequence number/letterto each command and and the pfodParserV3.17+ filters out any commands with duplicate sequencenumber/letter.
SomeBLE modules/software stacks drop bytes when sending long messages.
BLE V4 messages are limited to 20bytes per message.BLE V5 allows longer messages but it is very recent specification andmost of the software has not caught with it. Even if the module isadvertised as being V5 it probably still uses the 20byte limit.
Tosend long messages via BLE they need to be broken down into 20bytechunks and sent separately. You would hope/expect that module'ssupporting library would handle this for you. However in a number ofcases trying to send long messages requiring multiple chucks resultsin the end of the messages being dropped.
Bluetooth Serial Port
ThepfodParserV3.15+ library provided as pfodBLEBufferedSerial class that youcan insert between your prints and the BLE serial output to acceptthe full message and release it 20 bytes at a time very 200mS or so.This gives the BLE communication time to pass the message on to themobile.
Conclusion
Bluetooth To Serial Module
BLEoffers some unique advantages, very low power consumption, ifprogrammed correctly, and the promise of a local Mesh. However it isnot without is problems. If you only need to communicate between yourArduino project and your mobile or PC you are better off usingBluetooth Classic V2 or WiFi (IteadBluetooth Shield, OR Cheap/SimpleWifi Shield).
Ifyou really need to use BLE, or you want to stay on the “bleedingedge” of technology, then pfodAppremoves the need to code an Android app and the free pfodDesignergenerates all the code you need for a variety of BLE modules tocreate general purpose menus on your mobile. While the pfodParserlibrary and pfodBLEBufferedSerial over come double delivery ofcommands and loss of transmitted responses.
AndroidTMis a trademark of Google Inc. For use of the Arduino name seehttp://arduino.cc/en/Main/FAQ
The General Purpose Android/Arduino Control App.
pfodDevice™ and pfodApp™ are trade marks of Forward Computing and Control Pty. Ltd.
pfodDevice™ and pfodApp™ are trade marks of Forward Computing and Control Pty. Ltd.
A Bluetooth Serial Failure Has Occurred
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