ca926f00e0
This is not specifically an L1 example, but it lives beside the L1 "usart" example to show how easy it is to add semihosting support to existing code. Tested with the by now relatively old g-a-e 2012q4 release and OpenOcd 0.8.0-dev-00011-g70a2ffa (2013-05-14-19:41)
62 lines
2.0 KiB
Plaintext
62 lines
2.0 KiB
Plaintext
------------------------------------------------------------------------------
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README
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------------------------------------------------------------------------------
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This example program sends some characters on USART2 on the
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ST STM32L DISCOVERY eval board. (USART2 TX on PA2 @ 115200 8n1)
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It can _ALSO_ use semihosting to use regular stdio via the attached debugger.
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This expects you to be using gcc-arm-embedded from
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https://launchpad.net/gcc-arm-embedded
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Semihosting is a neat feature, but remember that your application will
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NOT WORK standalone if you have semihosting turned on!
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$ make ENABLE_SEMIHOSTING=0 will rebuild this image _without_ semihosting
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Semihosting is supported in "recent"[1] OpenOCD versions, however, you need
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to enable semihosting first! If you have not enabled semihosting, you
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will receive a message like this:
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(gdb) run
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The program being debugged has been started already.
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Start it from the beginning? (y or n) y
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Starting program:
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/home/karlp/src/libopencm3-examples/examples/stm32/l1/stm32l-discovery/usart-semihosting/usart-semihosting.elf
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Program received signal SIGTRAP, Trace/breakpoint trap.
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0x08000456 in initialise_monitor_handles ()
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(gdb)
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# Here we enable semi-hosting
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(gdb) mon arm semihosting enable
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semihosting is enabled
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(gdb) continue
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...
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You should now see the semihosting output in the window running OpenOCD.
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Size Notes
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~~~~~~~~~~
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Semihosting is basically free
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# Without
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$ arm-none-eabi-size usart-semihosting.elf
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text data bss dec hex filename
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29056 2212 60 31328 7a60 usart-semihosting.elf
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# With
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$ arm-none-eabi-size usart-semihosting.elf
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text data bss dec hex filename
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29832 2212 232 32276 7e14 usart-semihosting.elf
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The large size here is because of printf being included regardless, see
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nano.specs if you care about this, this data here is to show that semihosting
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doesn't cost much at all.
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[1] At least since OpenOcd version 0.8.0-dev-00011-g70a2ffa (2013-05-14-19:41)
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possibly earlier.
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