We have a target designed to use SWDIO SWCLK SWO (and NRST). We have to move this connector to a location 6 inches away from the STM32F uC. I cannot find any documentation about signal rise and fall times. Do I need to be concerned with signal integrity issues like matching trace impedance to ribbon cable impedance and using any series termination? Does anyone know of a document that addresses these concerns? I could not find any relevant material in the STLINK V3 documentation.
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\$\begingroup\$ Generally as a synchronous interface you should be able to dial back performance by using a slower clock speed, provided you don't see severe ringing. This distance doesn't sound ideal, and you might really reconsider trying to get things closer. That said, I've seen absurd cabling work. You might try adding footprints for optional terminal components (near the chip, not the connector). \$\endgroup\$– Chris StrattonOct 29, 2020 at 17:12
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I personally use STlink's with 6 inch ribbon cables all the time, it works fine. STLink's are designed to be used with these. You may want to use a lower clock speed but you probably don't need to.
If you're really concerned with reliability I'd caution against using low quality dupont jumpers. Not because there's anything inherently wrong with them electrically, but because they break easily. The crimps get loose easily, and they're often made with low-quality wire that can get severed internally (usually at the crimp).
