ANT minimum channel period on nRF51422

[Luca122131]

Hi, the ANT protocol defines the channel message rate in a range from 0.5Hz to above 200Hz, with the upper limit dependant on the specific implementation.

What are the limits for nRF51422?

I tried to use the ant_broadcast_rx_s210_pca10028 and the ant_broadcast_tx_s210_pca10028 examples and I added these:

sd_ant_channel_period_set(CHANNEL_0, PERIOD_VALUE_IN_MS);

in the static void ant_channel_tx_broadcast_setup(void) and static void ant_channel_tx_broadcast_setup(void) functions.

I tried to use different values for the PERIOD_VALUE_IN_MS const. I saw that if I use a value less than 100, the receiver miss few messages (I'm using the UART to print the received values) . At first I thought that the problem was the UART print function, but I tried to remove it and also the led on the receiver board blink really slow, so I thought the problem was the transmission rate.

Is there a way to send data at frequency of 100Hz ? I think that a byte could be enough.

Thanks!

EDIT: I can confirm that the Transmitter works fine also with a period of 10 ms (Message Rate of 100 Hz), the problem seems to be the Receiver.

[Petter Myhre]

The limits for the nRF51422 depend on a set of parameters, number and types of channels etc. But if you only have one transmit/receive channel, 200Hz should be achieveable. But you should test your setup to check that you actually achieve it.

I believe the usPeriod should be the period in 32768Hz counts. So for 4Hz you insert 32768/4=8192. While for 100Hz you insert 32768/100=327.68->328. If you insert 100 you will actually try to use a frequency of 327.68Hz.

Please let me know how it goes.

[Luca122131]

I think that's correct using 10 for 100 Hz because the period is defined:

Period = 32768 / MessageRate (Hz)

in D00000652_ANT_Message_Protocol_and_Usage_Rev_5

Am I wrong?

[Petter Myhre]

You want a message rate of 100Hz, then you need to set the channel period value to 32768/4 = 327.68->328. Just follow the example below equation 5-2.

[Luca122131]

Ok, thanks!