Trigger crossbar
2025-09-14 11:00
If you have a large, well-equipped electronics lab you’re going to have a lot of instrumentation with trigger input and output ports.
In my case all three oscilloscopes, the vector signal generator, and even my VNAs have trigger sync capability, and there’s probably more things I’m missing. And that doesn’t even count the ThunderScope or the two Siglent AWGs I have on loan for ThunderScope R&D.
Very often, it’s handy to cascade these in order to enable complex multi-instrument setups (for example, having a scope trigger when an AWG creates a pulse of some sort, without burning a scope channel to look at the AWG output, or to have two scopes trigger simultaneously to capture more channels of data in a complex system).
There’s just one obvious problem: All of my equipment is rack mounted, there’s a LOT of it, and there’s already a ton of cable spaghetti in a fairly confined space. The last thing I want to be doing is reaching around behind the racks and crawling under the bench to untangle coax and route trigger signals from one instrument to another every time I want to set up a multi-instrument experiment.
The second, slightly less obvious, problem is that not all of these signals are compatible voltage levels. For example, the trigger output on my Teledyne LeCroy oscilloscopes is 1V into high-Z or 500 mV into a 50Ω load. The Siglent vector signal generator has a 5V TTL trigger input. So you can’t just directly connect these without a level shifter or buffer.
What if there was a better way?
The concept
Pretty quickly I came up with a high level concept for what I wanted to build: a 1U device with an Ethernet SCPI interface plus a ton of coaxial trigger inputs and outputs, connected to a buffered FPGA-based switch fabric.
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