https://www.flir.com/support-center/iis/machine-vision/application-note/configuring-synchronized-capture-with-multiple-cameras/
From Dale:
It is straightforward, no extra circuitry or resistors or anything is required, and ALL cameras are wired the same (no "special wiring" for the "Master" camera -- because of the way things are wired, the software is free to pick any camera as the master). I'm including the wire color/function table here for the GPIO cable. Note that the numbers are the internal "Line"/bit numbers as used by the software. These are NOT the physical connector pin numbers (which we don't care about, since we have the nice colored wires to work with).
| Color |
I/O Line |
Function |
Description |
| Black |
0 |
OPTO-IN |
Opto-isolated Input |
| White |
1 |
OPTO-OUT |
Opto-isolated Output |
| Red |
2 |
GPIO |
|
| (or VOUT) |
Non-isolated Input/Output |
|
|
| (or power Output) |
|
|
|
| Green |
|
|
|
| 3 |
GPI |
|
|
| (or VAUX) |
Non-isolated Input |
|
|
| (or power input) |
|
|
|
| Blue |
N/A |
Opto GND |
Opto-isolated Ground |
| Brown |
N/A |
GND |
Camera Power Ground |
The wires should be connected together like this:
- GROUND: ALL the ** Blue** and Brown wires from ALL cameras should be connected together as a single circuit. This will connect the isolated and non-isolated grounds together. We don't need the isolation, and for the Strobe signal, we need to use an isolated I/O line together with a non-isolated one, so the grounds must be together.
- TRIGGER: The Red wires of all cameras should be connected together. This will be the shared Trigger line. It is nice that the RED line can be either an Input or an Output, so that the software can arbitrarily pick one camera to be the Master, and set its line to Output, and set all the other cameras to Input. The Master does not require special/different wiring from the rest of the cameras. Keeps things simple and flexible.
- STROBE: ALL of the White and Green wires from ALL cameras should be connected together as a single circuit. The Green line is a non-isolated input, which conveniently has an internal "pull up" resistor, so that it will normally "float high" at 3.3V. This works perfectly with the White "isolated" Output line, which is not capable of driving a voltage high, but it can pull a voltage low (it has a so-called "Open Collector" output). The software then picks any camera to be the Master, to use its White output line to drive the Strobe signal low on all of the Green lines.