85 lines
3.3 KiB
Markdown
85 lines
3.3 KiB
Markdown
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PyCortexMDebug
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==============
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*A set of GDB/Python-based utilities to make life debugging ARM Cortex-M processors a bit easier*
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It will consist of several modules which will hopefully become integrated as they evolve. Presently, there is only one:
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## SVD
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ARM defines an SVD (System View Description) file format in its CMSIS
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standard as a means for Cortex-M-based chip manufacturers to provide a
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common description of peripherals, registers, and register fields. You
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can download SVD files for different manufacturers
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[here](http://www.arm.com/products/processors/cortex-m/cortex-microcontroller-software-interface-standard.php).
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My implementation so far has only tested STM32 chips but should hold for others. If others are like those from ST,
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expect plenty of errors in the file. Like GPIOA having a register named GPIOB_OSPEEDR and lots of 16-bit registers
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that are listed as 32!
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The implementation consists of two components -- An lxml-based parser module (pysvd) and a GDB file (gdb_svd).
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I haven't yet worked out a perfect workflow for this, though it's quite easy to use when
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you already tend to have a GDB initialization file for starting up OpenOCD and the like.
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However your workflow works, just make sure to, in GDB:
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source gdb_svd.py
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svd_load [your_svd_file].svd
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These files can be huge so it might take a second or two. Anyways, after that, you can do
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svd
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to list available peripherals with descriptions. Or you can do
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svd [some_peripheral_name]
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to see all of the registers (with their values) for a given peripheral. For more details, run
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svd [some_peripheral_name] [some_register_name]
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to see all of the field values with descriptions.
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You can add format modifiers like:
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* `svd/x` will display values in hex
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* `svd/o` will display values in octal
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* `svd/t` or `svd/b` will display values in binary
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* `svd/a` will display values in hex and try to resolve symbols from the values
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All field values are displayed at the correct lengths as provided by the SVD files.
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Also, tab completion exists for nearly everything! When in doubt, run `svd help`.
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### TODO
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Enable writing to registers and individual fields
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### Bugs
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There are probably a few. All planning, writing, and testing of this was done in an afternoon. There may be
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some oddities in working with non-STM32 parts. I'll play with this when I start working with other
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controllers again. If something's giving you trouble, describe the problem and it shall be fixed.
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## DWT
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The ARM Data Watchpoint and Trace Unit (DWT) offers data watchpoints and a series of gated cycle counters. For now,
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I only support the raw cycle counter but facilities are in place to make use of others. As this is independent of the
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specific device under test, commands are simple and you can configure a clock speed to get real time values from
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counters.
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dwt configclk 48000000
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will set the current core clock speed. Then
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dwt cyccnt reset
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dwt cyccnt enable
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will reset and start the cycle counter. At any point
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dwt cycnt
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will then indicate the number of cycles and amount of time that has passed.
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## ITM/ETM support
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This is not implemented yet. I want to have more complete support for some of the nicer debug and trace features
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on Cortex-M processors. Parts of this will probably be dependent on OpenOCD and possibly on specific interfaces.
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I'll try to avoid this where possible but can't make any promises.
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