GPIO interface circuit - please clarify input/output direction

Answered

Derek Smith

• April 17, 2023 21:51

Hello, I'm interfacing a BlackFly BFS-PGE-16S2M-CS to a custom PCBA for control, and designing the control interface now. I read the BFLY-PGE-Technical-Reference sections, especially section 6. However, I'm a bit confused because the interface circuits shown (page 52, figure 6.2 & 6.3) are flipped in direction from what I would have thought. Figure 6.2 (opti-isolated input circuit) shows how OPTO_IN (pin 2) would be an OUTPUT from the camera, and an INPUT to another circuit. Correspondingly, figure 6.3 (opto-isolated output circuit) shows how a signal that is an OUTPUT from another circuit would go through an opto-isolator to become an INPUT to the camera on pin 4. What is correct?

I guess in the simplest implementation, to trigger the camera can I just use a relay between OPTO_IN (pin 2) and OPTO_GND, or does it need a voltage applied?

Also, can you please provide a bill of materials for the circuits shown in Figure 6.2 & 6.3 so I can copy them? Or the Altium files would do, since it looks like they're made in Altium.

Thanks,

Derek

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• Official comment

  

  TDY_Manuel

  Community team

  • April 18, 2023 07:53

  

  Hello Derek, 

  The BFLY (Blackfly) and BFS (Blackfly-S) are two different camera families. You can find the technical reference for your camera here: http://softwareservices.flir.com/BFS-PGE-16S2/latest/40-Installation/ElectricalGPIO.htm
  The circuits to the left are what is inside the camera so you do not have to copy them. 
  The opto pins actually need a TTL pulse to trigger the camera. If you use the non-isolated pins, you can short the input pin and ground to trigger the camera. 

  Best regards,

  Manuel 
• 

  Derek Smith

  • April 18, 2023 17:35

  Thank you, that makes it much clearer. For the Non-isolated input/output, the spec says that Output High Level is 0 to 24V. So if we are using it as an output of the camera and an input to our system (I think it's configured to be high during image exposure, like a strobe or something) then I will need to design the input circuit on our end to be able to survive up to 24VDC, correct?

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• 

  TDY_Manuel

  Community team

  • April 19, 2023 07:05

  

  The 24 V are just the maximum external voltage you can use if you want to use a pullup resistor, which is not necessary for the non-isolated output. Without it, you will get a 3.3V TTL signal.  Or you can chose whatever your circuit can handle. 

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