ANT Forum

Hi
Now, I implemented a heart rate transmitter on nRF51422 according to ANT+ heart rate monitor profile.
In my design, heart rate data was read from sensor at each one second. Following it, my firmware sent this heart rate data to ANTWareII slave. In ANTWareII, I set channel period is 8070 (4.06Hz).

The result is a lot EVENT)RX_FAILED(0x02) between correct heart rate packets.
I got some questioon about this issue

1. Although real heart rate data was read at every one second, it is still necessary to send ANT+ slave around
4 packets per second to prevent EVENT_RX_FAILED ? And, this 4 sequential packets have same content.
2. About sending out same 4 packets per second, s210/s310 sotware stack will automatically do it or
application code (user) needs to do it?

     

Hi Michael,

Your firmware should also be configured with a channel period of 8070 (4.06Hz) - this is a requirement of the ANT+ Heart Rate Device Profile. If you have your firmware set to transmit at 1Hz then you will typically see 3 RxFails between every received message.

Once the channel period is configured at this rate, then ANT will automatically transmit data 4 times per second. If you send new data from your sensor only once per second, then this same data will automatically be sent every 250ms until you send the next new data. The heart beat count is included in each message so that the receiver can distinguish new data from repeated data.

Transmitting at 4Hz is required because it reduces the search time required for a receiver to find your transmitter, and the repeated data reduces the risk of data loss in the case of interference.

Hope that helps,

Kat