ANT+ or BLE for a P2P application

[sslap]

Hi,

I'm designing a wearable, low power inertial and EMG system and have to choose between using ANT+ or BLE with the Nrf51422 on my own board.

The system would simply be a P2P with the wearable sending data for most of the time (Maybe receiving some small packages for settings at start). The data rate would be 11 byte at a speed of 1KHz so turning the Radio-module to sleep between transmitions is a possibility.

I have the evaluation kit so I have the possibility to use the Nrf51822 PCA10000 board or the ANT+ USB dongle as reciever. Range of the transmission is not important, 2 or 3 meters should suffice. Being able to connect to a smartphone or laptop without extra adaptor is an extra feature that would be nice but isn't necessary.

The most important feature is power consumption. The system would be using a battery so a lifetime of 24h is the minimum.

I'm using Eclipse and at the moment all the other modules are programmed but now I'm in the stage of communication and putting everything together.

I'm however still not sure which is best ANT+ or BLE and which Sofdevice protocol. I think BLE would be more power efficient and more secure but is more difficult to implement.

Does somebody has some arguments that I'm on the correct path or better change to ANT+

Many thanks

Sebastien

[Petter Myhre]

Are you using an nRF51 on both sides of the link? Or something else?

[sslap]

For the moment it is a Nrf51422 as sender and the Nrf51822 dongle as reciever (PCA10001). In a further design it will be two senders and one reciever

[Petter Myhre]

The ANT protocol is simpler. It is up to the application to implement more advanced features.

The BLE protocol is more complex, more robust, and more secure. It includes more advanced features.

Your question only includes information about the required data rate, which makes it very challenging to have an opinion on what protocol that is best for your application.

Edit 24.02: So you need a data rate of 88kbps, and you want to use as little power as possible.

If 88kbps is an absolute requirement, ANT can't be used, it has a maximum data rate of 60kbps, using Advanced Burst Data, please see Section 5.4.4 in "ANT Message Protocol and Usage".

With BLE, 128kbps is possible, please see this, but it depends on the devices.

Our peripheral stack(S110) can send 6 packets of 20B in each connection interval, and have a connection interval of 7.5ms.

However, our central stack(S120) can only recieve 1 packet of 20B in each connection interval, and have connection interval of 7.5ms.

This gives a data rate of 20*8/0.0075 kbps = 21.3 kbps. Not good enough.

Our development dongle can handle 6 packets of 20B in each connection interval, and have a connection interval of 7.5ms.

This gives a data rate of 20 * 8 * 6/0.0075 kbps = 128 kbps. Good enough, but our development dongle is not a standalone Bluetooth device, so you need driver on the PC to control it.

[Petter Myhre]

So your device needs to send 11 bytes every 1 ms? Which means a data rate of 11*8/0.001 kbps = 88kbps. And you need a lifetime of at least 24 hours. What kind of battery are you planning to use?

[sslap]

the battery isn't fixed yet but it would be a 3V or if needed 3.7V. I think the size of battery will more be specified by the needed power (it will be a rechareble battery that is certain)