ANT Forum

hello,
ANT uses TDMA to avoid the Channel collision by changin the time slot. the question here is:
if the collision happened near to master node with another device (not ANT) working in the same frequency how will the master node knows that there is a collision especially if he is sending broadcast.

the other case if the collision happend at the receiver, how the master will know that there is collision

thanks a lot      

Hi,

You seem to be a bit confused about what Channel Collision is with regards to ANT.

A channel collision occurs in circumstances where more than one channel tries to access the radio simultaneously and not all of the channels can be serviced. In this case, the EVENT_CHANNEL_COLLISION event will be detected (if it is supported by the device). From the receiving ANT node's point of view, this simply looks like an Rx Fail, as nothing was sent, so nothing could be received on that channel period. For more information refer to the AN15 Multi channel Design Considerations App Note .

What you are talking about (a 'collision' with another device) is interference, and will be seen as noise from an ANT point of view. In this case, you can expect an EVENT_RX_FAIL from the receiver's point of view, but only if the interference is significant enough to completely disrupt the message transmitted from the master node.

Cheers      

Thanks for the reply,
i thought that there are some detection methods if more than one ANT nodes working in the same area that allow the nodes to change sending time slot as in the case if there are multiple channel working on one node. so in order to avoid the interference i should use frequency agility.      

Hello,

ANT does have an internal mechanism that will detect if clock phases are shifting, or if there are encroaching transmissions from other masters in the same RF space. This mechanism is known as coexistence. Please refer to the presentation titled 'ANT Basics' at the bottom of the page here. I highly recommend taking a look at this video, as it gives a great visual representation of the coexistence mechanism, and it might help clarify the difference between coexistence and frequency agility.

Please note that the coexistence mechanism is for dealing with clock phase shifting between a synchronized master and slave, or dealing with many ANT devices in one area. Frequency Agility is used for dealing with interference in extremely hostile RF environments (i.e. another device's signal is interfering with an ANT transmission, NOT encroaching on the same RF space) by allowing the devices to jump channels when a hostile RF environment is detected. It is not generally recommended that you use frequency agility unless it is absolutely necessary for your application. You can get more information on frequency agility from 'AN10 ANT Frequency Agility Application Note' available here.

Cheers