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I need a USB to UART (TTL) cable for connecting to an onboard JTAG connector. Since I already own a Sigrok logic analyzer, I figure it might function soley as a USB to UART cable. Is this possible?

Here's my Logic analyzer:

https://learn.sparkfun.com/tutorials/using-the-usb-logic-analyzer-with-sigrok-pulseview/all

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  • \$\begingroup\$ Why are you trying to connect an asynchronous serial adapter to JTAG pins? JTAG is a synchronous interface. An FX2 chip as in your analyzer could do either but would need different firmware which may need adaptation. \$\endgroup\$ – Chris Stratton Sep 8 at 10:30
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USB-to-UART converter is an active device that reads AND sends data following some protocol.

Logic analyzers, by concept, only "sniff" the bus and can't generate active bus signals. In reality there are logic analyzers that have a "reversed" function and can generate traffic on their own, but they are called "logic exercisers" and need additional pre-designed firmware and software to follow bus protocols, all at substantial price mark-up.

Your "Sigrok" analyzer doesn't have this function, so the answer to your question is NO.

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The low cost USB device that you linked to is designed to be a logic analyzer and not a USB to TTL UART cable. In fact its usage even requires the use of specialized software to make it work that way. Sure the described usage of the logic analyzer allows it to be used in probing and analyzing the signal line protocols of a TTL UART interface but that does not make it a device with an alternate usage such as you desire.

Instead you should just simply purchase a purpose built USB to TTL UART cable. Fully professional cables of this sort can be purchased from reputable online suppliers for about the same price you paid for the low cost USB logic analyzer including the same supplier you linked for the logic analyzer. You can also purchase these from online sites like eBay for even less cost however these may or may not be as reliable and the USB driver software for the computer operating system may be questionable.

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  • \$\begingroup\$ As the "logic analyzer" is actually an MCU which can present a USB fifo on some of its GPIOs it has to have firmware downloaded from the host before it will do anything, it could be made to do this and more. It's unclear that asynchronous serial as in a USB UART is actually needed, at least if it is the mention of JTAG is mistaken. \$\endgroup\$ – Chris Stratton Sep 8 at 10:55
  • \$\begingroup\$ @ChrisStratton, yeah I'm following the same line of thinking. It's an interesting concept. \$\endgroup\$ – user148298 Sep 8 at 14:50

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