CC2640R2F: Bluetooth® 5 Is Here: Top Five Questions Answered

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Part Number: CC2640R2F

TI is pleased to announce general availability of the industry’s first single-mode Bluetooth® low energy production-qualified protocol stack supporting Bluetooth 5 High Speed mode (2 Mbps) for the SimpleLink™ CC2640R2F Bluetooth low energy wireless MCU. The SimpleLink CC2640R2 SDK 1.35, which includes the Bluetooth 5 protocol stack (BLE5-Stack) is available for immediate download at www.ti.com/tool/SIMPLELINK-CC2640R2-SDK and enables Bluetooth 5 development on the $29 CC2640R2 LaunchPad™ development kit.

We’ve put together some answers to common questions, including details on the Bluetooth 5 Throughput demo with High Speed and Long Range capability, to help enable developers to get started with Bluetooth 5 development. If you are new to Bluetooth or want to know more about the benefits Bluetooth 5, please check out our blog The secret to moving faster with Bluetooth® 5 and SimpleLink Academy.

Throughout this article, “Bluetooth” refers to Bluetooth low energy unless otherwise stated.

[Updated 23-May-17] Watch a short demonstration video of the High Speed and Long Range capability of TI's Bluetooth 5 protocol stack on Facebook here.

 

Is Bluetooth 5 backwards compatible with existing Bluetooth 4.x devices?

Yes! As with all features added in the Bluetooth 4.1, 4.2 and 5 specifications, they are optional and negotiated during the BLE connection. This ensures that Bluetooth 5 devices can reliably connect to and interact with legacy Bluetooth 4.x devices. In addition to backwards compatibility, optional features in Bluetooth 4.1 and 4.2 apply to Bluetooth 5. So, Bluetooth 5 devices may support the Data Length Extension feature from Bluetooth 4.2 in addition to the 2 Mbps feature. The TI BLE5-Stack incorporates all previous features from the existing Bluetooth 4.1 and 4.2 protocol stacks, including enhanced privacy and Secure Connections pairing.

 

How do I enable Bluetooth 5 High Speed Mode in my application?

The good news is you only need to call one new API in your application to request a BLE connection to use the 2 Mbps PHY: HCI_LE_SetDefaultPhyCmd(). This will instruct the Controller (Link Layer) to initiate what’s known as the PHY Update Procedure shown in the diagram below and is the sequence of steps that both peer devices perform to negotiate a change to the the link speed. If both devices in the connection support and prefer the 2 Mbps PHY, you’re in luck and the connection will switch over to the 2 Mbps link speed with data packets transmitted in half the time as compared to the default 1 Mbps link speed. If the peer device doesn’t support the 2 Mbps feature, or does not wish to enable it, the connection will remain at the BLE-default 1 Mbps link speed. All APIs for exchanging data (i.e., GATT) remain the same in Bluetooth 5.

We’ve put together a LE 2M PHY guide within our BLE5-Stack SW User’s Guide with all the details on how to call this new API. Check it out here.

But wait, we’ve also enhanced our Throughput Demo on GitHub to add support for Bluetooth 5 High Speed and Long Range modes. This demo runs on two CC2640R2 LaunchPads and allows the user, via the two-button menu on the LaunchPad and a virtual serial port display to toggle between the supported PHYs while recording payload throughput and RSSI.

 


PHY Update Procedure

What range should I expect with High Speed Mode?

You may have heard that 2 Mbps connections may have “shorter range” than 1 Mbps connections. The physics behind this is quite complex, but it is true that any PHY (radio) operating in 2 Mbps mode will have 5 dB less sensitivity as compared to the PHY operating in the default 1 Mbps mode. While this may sound like a substantial loss in performance, it’s important to note that the improvements in the CC2640R2F’s radio architecture, including best-in-class RF performance, ensure high performance in personal connectivity / in-room operating environments where Bluetooth is typically used. This means you should expect greater throughput with High Speed mode at comparable distances as first generation Bluetooth 4.0 devices operating at the default LE 1 Mbps link speed.

It’s worth mentioning that another often overlooked feature in Bluetooth 5 is the Channel Selection Algorithm 2, or CSA2, that improves the BLE frequency hopping algorithm. This feature, which is supported with the TI BLE5-Stack, can reduce the impact of ‘bursty’ interference from other transmitters in the shared 2.4 GHz spectrum by ensuring that each connection event occurs at a minimum frequency offset compared to the previous connection event. Reducing packet loss from interference can reduce the number of packet retransmissions and thus improve overall energy consumption / effective throughput. Please note that the “Slot Availability Mask” feature applies to classic Bluetooth devices only and is therefore not supported by the CC2640R2F.

 

How do I evaluate Long Range mode?

In addition to the High Speed 2 Mbps mode supported in the BLE5-Stack v1.0 protocol stack, TI has also enabled the ability to evaluate the LE Coded PHYs which are used to enable longer range Bluetooth connections at the same transmit power. The longer range is enabled by using Forward Error Correction (FEC) to improve receiver sensitivity. If you want to know more about the science behind coded PHYs and how they improve link budget without increasing transmit power, check out our blog How does Bluetooth® 5 increase the achievable range of a Bluetooth low energy connection? which includes a video demonstration of a 1.6 km BLE Long Range connection between CC2640R2 LaunchPads.

To enable the evaluation of the LE Coded PHYs in the SDK, enable the feature in the protocol stack’s build_config.opt file. Connections are established at the default 1 Mbps link speed (same as Bluetooth 4.x) and then can be switched to a LE Coded PHY via the PHY Update Procedure. Use of the LE Coded PHYs is also demonstrated in the Throughput Demo on GitHub. Evaluating the LE Coded PHYs will help you to measure actual performance your device will expect to achieve in the long range configuration.

Please note that you cannot certify your device with Bluetooth SIG when using the LE Coded PHY evaluation configuration from this SDK. TI intends to provides updates to the BLE5-Stack at a later time which will include additional features, such as Advertising Extensions, required to support a Bluetooth 5 LE Coded PHY certification.

 

What about Mesh?

Mesh, which was announced last year by the Bluetooth SIG as an upcoming feature, is not part of the Bluetooth 5 specification and has yet to be adopted by SIG. To keep up on the latest status with Mesh, TI recommends creating a free Bluetooth SIG account and subscribing to announcements from Bluetooth SIG.

 As you can see with all these great improvements Bluetooth 5 is not your father’s wireless specification. Please feel free to ask questions below.

Please see the TI BLE Wiki www.ti.com/ble-wiki and sticky forum threads for additional examples & answers to most common questions!

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