We have multiple STM32 uC on board and would like to share as many connections for programming the parts.

[JTrau.1]

Is there a way to connect them in parallel with some individual enable to reduce the outward interface of the board. ie maybe connect everything in parallel except for RST line or ??? any suggestions would be appreciated

[Ozone]

JTAG can be daisy-chained.

I would suggest to consult the JTAG standard, I never used that feature myself.

Or start e.g. here: http://www.pemicro.com/blog/index.cfm?post_id=136

[JTrau.1]

I see some info on web that suggests STlink cant handle this connection for programming parts, but perhaps other debugger/programmers can?

[Tesla DeLorean]

Really a software issue.

You'd need more industrial software rather than low-rent consumer stuff.

Segger used to have libraries for industrial/automation users, and specialized JTAG experience is out there in the test/measurement world, but expect to have to pay for it.

[JTrau.1]

we currently also have a seggar unit. How would we connect up the JTAG/SWD interface? Our current connection uses JTD)/TRACE_SWO, JTCLK/SW_CLK, JTMS/SWD_IO and RST. Would we connect all of these in parallel? ie all trace lines together, all CLK lines together and all SWDIO lines together? i wish they had good documentation on this.

[Tesla DeLorean]

JTAG, daisy-chained, ie serial and *not* parallel

http://www.pemicro.com/blog/index.cfm?post_id=136

[JTrau.1]

understand, the TDI and TDO are serialized, but the other two lines are paralleled, for JTAG, but currently it looks like we are only using the SWD interface which is SWDIO (sits on JTMS lines), SWCLK (sits on JTCLK), TRACESWO (sits on JTDO line). we currently dont use the JTDI line which I guess is not used for SWD

[waclawek.jan]

Which STM32?

Can't the factory bootloader be used in some way?

JW

[Tesla DeLorean]

Yes, going to need to use JTAG, not the simplified/subset of functionality from SWD

[Tesla DeLorean]

Yes, I expect one could mux the UART connection, or selectively hold devices in reset so that one could be programmed at a time.

Could mux TX outputs with diode tree and pull-up