GPIO (General Purpose Input/Output)

• GPIO (General Purpose Input/Output)

 

 

 

- A programmable electrical pin used for communication between hardware devices. It lets a device send or receive electrical signals.

- The reason why it exists is a camera alone cannot know :

• when an object arrives
• when a robot arm moves
• when a laser fires
• when another camera captures

So, GPIO allows hardware synchronization.

---

• Two Main GPIO Modes 

 

Mode	Meaning
Input	receive signal
Output	send signal

 

- GPIO Input & Output Example :

 

1. GPIO Input Example :

 

Suppose a camera sensor detects a passing object.

Camera Sensor ─────> Camera GPIO Input

When object arrives :

• sensor outputs HIGH pulse
• camera receives trigger

This becomes :

TriggerSource = Line1

---

2. GPIO Output Example : 

 

Camera can also output signals.

Camera GPIO Output ─────> LED Strobe

When exposure starts:

• camera outputs HIGH
• flash turns ON

This synchronizes lighting with image capture.

---

• Industrial Camera GPIO

 

- Most industrial cameras have :

isolated trigger pins
opto-isolated inputs
output lines
strobe outputs

 

- And Typical connector :

Line0
Line1
GND
+12V
Output0

 

In GenICam SFNC, GPIO lines are usually called :

Name	Meaning
Line0	GPIO pin 0
Line1	GPIO pin 1
Line2	GPIO pin 2

 

So, 

TriggerSource = Line1

means trigger signal comes from GPIO Line1

---

- GPIO Timing Example :

 

 

1. Free-run Camera :

Camera captures continuously

 

2. GPIO Triggered Camera :

Sensor pulse
     ↓
GPIO HIGH
     ↓
Camera captures frame

 

Timing :

GPIO Signal
____|‾‾‾|____

Camera Exposure
________|‾‾‾‾

---

• GPIO Signal Types

 

1. Pulse Signal

 

Short HIGH pulse:

____|‾|____

 

2. Level Signal

 

Signal stays HIGH:

____|‾‾‾‾‾|____

---

• Camera Hardware Trigger

 

Photoelectric Sensor
        ↓
GPIO Line1
        ↓
Industrial Camera

 

GenICam :

TriggerMode       = On
TriggerSource     = Line1
TriggerActivation = RisingEdge

---

• GPIO and Edge Detection

 

Event	Meaning
RisingEdge	LOW → HIGH
FallingEdge	HIGH → LOW

 

Example :

LOW ____|‾‾‾
          ↑
      RisingEdge

And this directly connects to:

TriggerActivation = RisingEdge

---

• GPIO synchronization

 

LiDAR PPS Signal
      ↓
GPIO Trigger
      ↓
Camera Exposure
      ↓
Aligned sensor timestamps