ANT Forum

Hi,

I am working on nRF51422 with SDK 5.2.0 and softdevice S310. My one device work as a ANT Master with channel ID (1,1,2) and channel period of 4 Hz. Other 4 device work as a ANT slave with channel ID (1,1,2) and channel period of 4 Hz.Radio frequency is 2466 MHz. I am using shared address channel mode. So each ANT slave device have shared address. Master send message to shared address devices in following manner.

Master sends broadcast message to address 0 --- all shared slaves receive it

Master sends Ack message to address 1 --- slave 1 receive it

Master sends Ack message to address 1 --- slave 1 receive it

Master sends broadcast message to address 0 --- all shared slaves receive it

Master sends Ack message to address 2 --- slave 2 receive it

Master sends Ack message to address 2 --- slave 2 receive it

Master sends broadcast message to address 0 --- all shared slaves receive it

Master sends Ack message to address 3 --- slave 3 receive it

Master sends Ack message to address 3 --- slave 3 receive it

Master sends broadcast message to address 0 --- all shared slaves receive it

Master sends Ack message to address 4 --- slave 4 receive it

Master sends Ack message to address 4 --- slave 4 receive it

Master sends broadcast message to address 0 --- all shared slaves receive it

Master sends Ack message to address 1 --- slave 1 receive it

Master sends Ack message to address 1 --- slave 1 receive it

.................................................

................................................. repeat sequence again

My problem here is that when master send a burst message to any slave device, sometime it transfer to that particular slave in one try and sometime it takes 5 retry. Same thing happens during transfer of burst message from slave to master. my burst failure ratio is 4 out of 10. I cant understand why this happen. Is any hardware or software related consideration I have to take care? Please guide me.

Thanks
- Bipin      

Does orientation and distance between the master and slaves change the burst failure rate? If you are using a custom RF design, is the antenna tuned yet? This may have a significant impact in the RF performance.      

Sorry for late reply due to diwali Holidays in India.

Orientation and distance make difference but even in range of 2-3 feet, burst failure occur. i am using ready-made ANT module from dynastream, so i think there will be no issue of RF design.      

What is the actual burst failure rate that you see at 2-3 feet range?
Have you tried using a different RF frequency - you may be dealing with interference from other sources (e.g. WiFi network).      

1. actual burst failure rate was nearly 15% at 2-3 feet range.
2. After that i have tried with frequency agility(10,40,70) so i get considerably improvement in burst transfer. failure ratio gets down to 5% without retry on failure at application level. If i put retry logic only for one at application level then i get max 2% failure.
3. One thing i would like to mention here is that i am using nordic chip nRF51422 which support ANT+BLE stack. so BLE stack is running in my device.
4. WiFi network is continuous around us as all engineers are using internet through WiFi.

Is any other things we can do to achieve 100% success ratio.      

If you are actively running BLE on the same device, you are going to see decreased performance in both - the two protocols are sharing the same radio and there will be situations where they need to use it at the same time and only one of them will get to do so. You can confirm how much coexistence is contributing to the problem by doing a test with BLE disabled.

Please also be aware that in wireless connections it is not possible to achieve a 100% success rate all the time. Losses are inherent to wireless systems, and applications using wireless need to be designed with that in mind..      

With BLE disable, failure ratio goes down.

Thanks for support

-Bipin      

hi,

I am using NRF51422 module. with "s310_nrf51422_1.0.0_softdevice" and shared channel configuration with single master and multiple slave(max 4 slave).

Master side:
1. The burst sending failure rate for is 20% without retrial.
2. the burst sending failure rate is 9% with single Application level retrial

Slave side
1. The burst sending failure rate is 4% without retrial.
2. the burst sending failure rate is 0.8% with single Application level retrial

I don't know why at master side i get this much of burst failure. Master only takes message from UART and send it to Slave.

Can u suggest what could be the possible reason for this much of failure? Does it due to any synchronization mismatch with slave?

Note:
In Master device firmware, Only single ANT channel is active.
For slave device both ANT and BLE are active.
I am sending 72 bytes burst in a single shot.
Chanel period used is 4Hz and burst sending interval is 15Second.