ANT Forum

Hi,

I'm working on a design much like TI's Health and Fitness Aggregator Platform, in that we want to take data from possibly several remote devices via ANT and transmit the information to a single Bluetooth host.

I have no problem talking Bluetooth and ANT separately, but when i try to do them both the ANT device returns EVENT_RX_FAIL most of the time, even at relatively low data rates. It looks like TI's HRM demo runs at 4Hz, are there known limitations that require this data rate? We can run the ANT interface alone at 100Hz, but even at 10Hz we have problems while also connected to our BT host. We aren't transmitting any data yet over the Bluetooth connection, merely opening the SPP link, and immediately see problems with the ANT interface.

Does anyone have experience running the PAN1327 in both ANT and Bluetooth mode simultaneously?

Thanks!
Robby      

Hi Robby,

The HRM Device Profile spec defines other data rates you may use to read HRM sensor data, which you can find here.
EVENT_RX fails will occur when you attempt to use both ANT and Bluetooth simultaneously on the CC2567 as they both have to share the same radio. ANT will attempt to take enough priority to maintain it's channel links but increased Bluetooth activity will inevitably cause some disruption to ANT messaging.

Cheers,
Harrison      

Thanks Harrison,

This is great information, here is my experiment:

We have an ANT device configured to transmit some sensor data at 5Hz, and another (MSP430-PAN1327) device configured to receive the data.

When I get both running, I have some debug indication for the success rate of the ANT reception on the MSP430, and everything seems to be running fine (RX_FAIL type errors are <1%, if at all). I initiate the BT connection from a third device to establish an SPP connection with the MSP430. I don't explicitly transfer any data yet, but the ANT connection is now dominated with RX_FAILures.

So, you think there is still significant radio use by the underlying layers of the BT stack while the SPP connection is open? Enough to cause most of the ANT packets to be broken? Is there any way to work around this? Can the priority of the ANT communications be given any more priority, or can the BT connection be put on hold while still being connected?

Thanks for all your help!

Robby      

Hi Robby,

What kind of failure rates are you seeing?
I'm not entirely familiar with the behaviour of the SPP, but if Bluetooth is doing scanning and it lines up with the 5 Hz period of the ANT messaging then the Bluetooth will interfere with it, the SPP may be doing alot of scanning to maintain it's link.

Cheers,
Harrison      

Thanks again for the reply,

The failure rate at 5Hz is about 50%, 10Hz is about the same, and 50Hz is significantly more, 90% failure or so.

I will look deeper into what may be going on from the BT side.

Thanks again for your help!

Robby