[ell-i-developers] Re: OpenOCD and ellduino

  • From: Pekka Nikander <pekka.nikander@xxxxxx>
  • To: ell-i-developers@xxxxxxxxxxxxx
  • Date: Sun, 8 Jun 2014 15:06:33 +0300

> I think SWD is better but JTAG programmer/debuggers are more common.
> The next generation boards are going to include other parts than just
> the MCU that support JTAG and none of them have SWD. That pretty much
> means we need all JTAG pins.

> From what I’ve understood, the SWD and JTAG are pretty much the same
> from semantic point of view, but their signaling at "lower layers"
> are different. I think they have 1:1 mapping, so supporting both should
> not be too hard.

At least in STM CPUs SWD is a subset of JTAG, repurposing the JTAG TMS for 
SWDIO and TCK for SWCLK.  The low-end STM32 MCUs don't include full JTAG 
support, but they do include SWD support.  I haven't studied other 
manufacturer's dies, so I don't know about them.  The Baselli schematics has an 
example of how to wire them.


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