ANT Forum

Hello all!

I am working on a custom ANT network project using the Dynastream N5 ANT SOC modules. My system requirements is that I connect 8 ANT slaves to one ANT Master, and retrieve data from each slave at about 45 Hz. In other words, each one of the 8 slaves has to transmit at 45 Hz.

Looking through the ANT Interface document, I have decided to use shared channels. Most of the time, only the slaves will transmit to the master, and master will rarely have to transmit data to the slaves. To meet the 45 Hz requirement, I am thinking about using two shared channels, with each channel frequency being set to the maximum allowed ~190 Hz. I am planning on connecting 4 slaves per channel, to achieve ~45 Hz (190/4) transmission rate from each slave. The data that the slaves are transmitting will be rapidly changing.

I am attaching a diagram of the network topology I mentioned. Is what I mentioned possible with this setup? I have my concerns about whether one ANT module can handle 8 slaves at 45 Hz data rate each. I am new to ANT and I would love some advice from some ANT fellows!


Thanks!

-AEO
     

Hi AEO,

The 192 Hz spec for the N5 module is not only a relative per channel limit, but it is also close to the total timeslot limit of the nRF51422 chipset itself, not taking into account if you use acknowledged or burst messages as well, or mixed master & slave channels. If you do use ack messages in the forward and reverse directions then you would likely need to halve your total messaging again. Assuming broadcast only messages for a single device with only a master or multiple master channels, you can support 4 slaves at 45Hz each, or 8 slaves at 24 Hz each, beyond that you will see dropped messages.

Cheers      

Hello Harrison!

Thanks for the reply. Is there an ANT module you could recommend me that has a higher total time-slot limit, or is 192 Hz a limitation of the ANT protocol?      

300 Hz/RF channel/same area is generally considered the over the air limit before multiple channels start bumping into each other, but 200 Hz is generally the limit for a device due to the required radio time for sending/listening to messages. You could achieve higher than this using tx/rx only channels (closer to 800 Hz), especially on a ANT/WiFi device, but this would disable ANT isochronous coexistence which I wouldn't recommend as you have multiple devices running doing bi-directional communication.

Nordic also provides a proprietary protocol called Gazelle which can also run on the N548 module. While I am not familiar with it, Nordic typically recommends it for very specialized applications.      

Hello Harrison,

Thanks again for the reply. I have decided to use continuous scanning mode on my hub, and making masters broadcast data.

I will have several ANT modules as hubs, each on continuous scanning modes at different frequencies servicing 2-3 masters each. I am having some dropped data that I have questions about, but I will create another thread about that.

Is there an ANT module you would recommend me to use as continuous scanning slaves? The C7 modules claim to have "High density node support – up to 300 nodes at 1 Hz Tx rate in same RF space" but has lower receiving sensitivity compared to n51SoC (-86 dbm vs. -90 dbm). Which one would you recommend? I am wondering which one would perform better and pick up packets more reliably.

Thanks!      

Hi,

This depends on your setup. If ANT messages are spaced very closely in time together, they may not be pushed out over the serial connection fast enough and may be lost. If you use the N5 module as an SoC. then it's a better choice as there are no more concerns about serial speed in that case.

Edit: The N5 Module also supports higher speed SPI modes, so both modules could be equally useful as a continuous scanning node with a host microcontroller.

Cheers      

Hi Harrison,

I am planning on using the N5 module as the remote master transmitters, and was looking into using the C7 as the continous scanning slave that gathers all the data from masters, and transmits to an MCU Host. Is that what you mean by using C7 as network processor?      

Yes, by "network processor" I am referring to the MCU host controlling the module, rather than use the module as an SoC.

As per my correction above though, the N5 module does also support up to 8MHz SPI, so the N5 module may also be used as the continuous scanning node.      

Thanks for the reply! I looked through the N5 data sheet, and I see that N5 supports up to 4 Mhz SPI. I also tried interfacing N5 through UART, and the fastest speed I could get was 57600 Baud, even though the datasheet claims that N5 supports 115200 Baud. None of the BR1/BR2/BR3 combinations matched the UART speeds defined in the datasheet, do you know why I am running into this issue?      

The network processor code is designed to mimic the interface for the AP2 module, which only supports up to 57600 using the BR1, BR2 and BR3 pins.      

Hello Harrison,

Thanks for the continued support. I am attaching a snip from the N5 Datasheet. According to it, 1-0-0 configuration for BR3-BR2-BR1 should give me 115200 baud rate, but it didn't. Do you know how I can use that speed? Am I doing something wrong?      

at least my custom module works:

nRF51422 QFAA E0
s210_nrf51422_4.0.1_softdevice.hex
ant_network_processor_s210.hex
     

Hi AEO,

Were you able to resolve this issue?