I'm trying to configure a STM32F400 board so that I can read from
the Cortex Debug + ETM using the gpio pins. Is this possible? The
pins are so small that it would be difficult if not impossible to
read from those pins when the J-Trace is plugged in. Please let me
know if you know of any resources that can help me accomplish
Not sure what kind of hackery you're trying here, but aren't those
same pins exposed as jumpers or other places on the board.
The processor can read the pin levels via GPIO->IDR, but this
stuff is pretty fast moving and best probed with an FPGA or logic
The alternative is to use an intermediate cable/board
(interposer?) so you can access the pins with a header pitch you can
Thanks for your response. The J-trace has j-tag and cortex debug
+ETM support, I am interested in the latter. The stm board has inputs
for cortex debug, cortex debug + ETM, and JTAG. The J-trace's plug
fits very snugly into the cortex debug +ETM port but with the pins
being so close and the fit being so snug, it doesn't seem practical
to run wires parallel to that port.
From your response, I take it that the GPIO IDR solution won't be
sufficient for any real time application.
So i guess the next best thing is an intermediate board where
there would be more room to work with, although that presents its own
challenge of needing the proper connector to go from the intermediate
board to the stm board. The reason I need to access these pins is for
a PhD student I'm working with this summer. She wants to be able to
access the pin information from two methods simultaneously.
Not tinkered with this in recent years, but the trace data is a
fire-hose data source, so you need some means/method to capture it,
and then to process it.
This isn't an olden days ICE type trace, but rather a
reconstructive process where you're holding copies of the on board
memories, and replicating transactions into a state model of the
I'd probably go with the pass-thru interposer method, and buffer
into an FPGA or FIFO memory.
Perhaps find a different F4 board which you can get to the SWDIO,
SWCLK and TRACE pins more directly?
Or a board exposing the pins?
I have found this type of adaptor useful for adapting that kind of
small connector up to 0.1" pitch:
You could use a 2nd one to adapt back down again for a
pass-through board ...
Relly helpful for me. I will buy this one
www.segger.com/.../ for my
connector to 0.1 pitc.
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