S

M

M0212-01

Master

Time

Time

T0496-01

Slave

Channel TimeSlot

(Always)

Forward

Direction

(Optional)

Reverse

Direction

t

ch

t

ch

t

ch

CC2570

CC2571

www.ti.com

SWRS095A

– FEBRUARY 2011 – REVISED MARCH 2011

ANT CHANNELS

ANT channels are the fundamental building blocks of ANT networks. An ANT channel is a logical connection

between two ANT nodes. ANT channels are fully independent, meaning that multiple channels can form a

network without the need for a central coordinator or a network master, with each channel managing itself

relative to other channels in the RF space. A single ANT node can support multiple channel endpoints, each

completely independent of the other, allowing master and slave combinations on a single device. ANT channels

are also ad hoc, allowing connections to be created and destroyed on an as-needed basis.

Figure 3. ANT Channel

An ANT channel is formed between a master and a slave endpoint (Figure 3). The master endpoint is the

communication initiator and controls the channel. The master is often referred to as the primary transmitter, as it

is always transmitting a data packet at a specific channel period to keep the channel synchronized. The channel

period can vary from 0.5 Hz to 200 Hz and can be changed dynamically by the application host MCU. Each data

packet carries exactly 8 bytes of application data payload. The slave endpoint is the communication acceptor, or

primary receiver. It searches for master transmissions and then synchronizes to the master at the channel period

of the master, or a multiple thereof. The slave only transmits data to the master if it is instructed to do so by the

application MCU. Figure 4 illustrates the behavior of a bidirectional synchronized ANT channel.

Figure 4. ANT Channel Timing

The search algorithm used by the slave to find the master has been specifically designed to optimize battery life.

The slave duty-cycles its radio at a specific rate to trade off acquisition latency for power consumption, allowing

for prolonged searches that can still operate on a coin cell battery.

Each packet transmitted by ANT is characterized by the following parameters:

•

8-byte data payload

•

Frequency (2400 MHz to 2485 MHz)

•

2-byte network key

•

4-byte channel ID

Each of these parameters can be changed by the application MCU between message periods.

Copyright

© 2011, Texas Instruments Incorporated

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