Point Grey Flea3 GigE Technical Reference
6 Input/Output Control
6.4
Programmable Strobe Output
The camera is capable of outputting a strobe pulse off select GPIO pins that are configured as outputs. The start of the
strobe can be offset from either the start of exposure (free-running mode) or time of incoming trigger (external trigger
mode). By default, a pin that is configured as a strobe output will output a pulse each time the camera begins integration
of an image.
The duration of the strobe can also be controlled. Setting a strobe duration value of zero produces a strobe pulse with
duration equal to the exposure (shutter) time.
Multiple GPIO pins, configured as outputs, can strobe simultaneously.
Connecting two strobe pins directly together is not supported. Instead, place a diode on each strobe pin.
The camera can also be configured to output a variable strobe pulse pattern. The strobe pattern functionality allows
users to define the frames for which the camera will output a strobe. For example, this is useful in situations where a
strobe should only fire:
n
Every Nth frame (e.g. odd frames from one camera and even frames from another); or
n
N frames in a row out of T (e.g. the last 3 frames in a set of 6); or
n
Specific frames within a defined period (e.g. frames 1, 5 and 7 in a set of 8)
Title
Article
Buffering a GPIO pin strobe output signal using an optocoupler to drive external
devices
Knowledge Base Article 200
GPIO strobe signal continues after isochronous image transfer stops
Knowledge Base Article 212
Setting a GPIO pin to output a strobe signal pulse pattern
Knowledge Base Article 207
Related Knowledge Base Articles
6.5
Pulse Width Modulation (PWM)
When a GPIO pin is set to PWM (GPIO Mode 4), the pin will output a specified number of pulses with programmable
high and low duration.
The pulse is independent of integration or external trigger. There is only one real PWM signal source (i.e. two or more
pins cannot simultaneously output different PWMs), but the pulse can appear on any of the GPIO pins.
The units of time are generally standardized to be in ticks of a 1.024 MHz clock. A separate GPIO pin may be designated
as an “enable pin”; the PWM pulses continue only as long as the enable pin is held in a certain state (high or low).
The pin configured to output a PWM signal (PWM pin) remains in the same
state at the time the ‘enable pin’ is disabled. For example, if the PWM is in a
high signal state when the ‘enable pin’ is disabled, the PWM pin remains in a
high state. To re-set the pin signal, you must re-configure the PWM pin from
GPIO Mode 4 to GPIO Mode 1.
To control PWM:
n
CSRs—
GPIO_CTRL_PIN: 1110h-1140h
and
GPIO_XTRA_PIN: 1114h-1144h
Revised 10/29/2013
Copyright ©2010-2013 Point Grey Research Inc.
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