1.3. Wiring the Talon SRX Signal Input
The Talon SRX is capable of being controlled using either CAN bus or a PWM signal. Each input type
has its own pros and cons that should be carefully considered before wiring and programming.
The CAN bus capability of the Talon SRX is one of its most powerful features. It allows up to 63 Talon
SRXs to be daisy chained – this means Talon SRXs can plug into each other and only require a
single output on the primary robot controller. CAN bus also allows two-way communication between
the Talon SRX and the robot controller, which enables tasks like field-upgrade, Data Port
configuration, dynamic Brake/Coast toggling, and motor control. When using CAN bus, sensors that
are connected to the Data Port are monitored by the Talon SRX meaning that the primary robot
controller has more processing power to devote to other tasks.
One of the simplest ways to control a Talon SRX is using a Pulse Width Modulation (PWM) signal.
Unlike CAN bus control, using PWM requires that each Talon SRX must be individually connected to
a different output on the system’s primary robot controller – Talon SRXs cannot be daisy chained in
PWM mode. When using PWM to control the Talon SRX, only limit switches (or equivalent binary
switches) may be used with the Data Port. Encoders or Analog sensors cannot be used.
1.3.1. Configuring a Talon SRX with CAN bus on a roboRIO
Talon SRX automatically detects CAN bus traffic so there is no need to select “CAN” vs “PWM”. The
only configuration that is necessary is assigning Device IDs to prevent common-ID Talons (more than
one Talon with the same device ID). This is a common problem condition that prevents reliable
communication between the primary robot controller and other CAN devices.
However the roboRIO Web-based Configuration page is tolerant of common-ID Talons to a degree
(up to typically five or less common-ID Talons), so you can discover, firmware update, modify settings,
and change the device ID of a common-ID Talon to an unused device ID. More information can be
found in the Software Reference Manual.
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