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70 lines
3.2 KiB
ReStructuredText
70 lines
3.2 KiB
ReStructuredText
High-Level Interrupts
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=====================
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.. toctree::
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:maxdepth: 1
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The Xtensa architecture has support for 32 interrupts, divided over 8 levels, plus an assortment of exceptions. On the {IDF_TARGET_NAME}, the interrupt mux allows most interrupt sources to be routed to these interrupts using the :doc:`interrupt allocator <../api-reference/system/intr_alloc>`. Normally, interrupts will be written in C, but ESP-IDF allows high-level interrupts to be written in assembly as well, allowing for very low interrupt latencies.
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Interrupt Levels
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----------------
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===== ================= ====================================================
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Level Symbol Remark
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===== ================= ====================================================
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1 N/A Exception and level 0 interrupts. Handled by ESP-IDF
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2-3 N/A Medium level interrupts. Handled by ESP-IDF
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4 xt_highint4 Normally used by ESP-IDF debug logic
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5 xt_highint5 Free to use
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NMI xt_nmi Free to use
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dbg xt_debugexception Debug exception. Called on e.g. a BREAK instruction.
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===== ================= ====================================================
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Using these symbols is done by creating an assembly file (suffix .S) and defining the named symbols, like this::
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.section .iram1,"ax"
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.global xt_highint5
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.type xt_highint5,@function
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.align 4
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xt_highint5:
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... your code here
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rsr a0, EXCSAVE_5
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rfi 5
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For a real-life example, see the :component_file:`esp_system/port/soc/{IDF_TARGET_PATH_NAME}/dport_panic_highint_hdl.S` file; the panic handler interrupt is implemented there.
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Notes
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-----
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- Do not call C code from a high-level interrupt; because these interrupts still run in critical sections, this can cause crashes.
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(The panic handler interrupt does call normal C code, but this is OK because there is no intention of returning to the normal code
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flow afterwards.)
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- Make sure your assembly code gets linked in. If the interrupt handler symbol is the only symbol the rest of the code uses from this
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file, the linker will take the default ISR instead and not link the assembly file into the final project. To get around this, in the
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assembly file, define a symbol, like this::
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.global ld_include_my_isr_file
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ld_include_my_isr_file:
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The symbol is called ``ld_include_my_isr_file`` here but can have any arbitrary name not defined anywhere else.
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Then, in the component CMakeLists.txt, add this file as an unresolved symbol to the ld command line arguments::
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target_link_libraries(${COMPONENT_TARGET} "-u ld_include_my_isr_file")
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If using the legacy Make build system, add the following to component.mk, instead::
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COMPONENT_ADD_LDFLAGS := -u ld_include_my_isr_file
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This should cause the linker to always include a file defining ``ld_include_my_isr_file``, causing the ISR to always be linked in.
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- High-level interrupts can be routed and handled using esp_intr_alloc and associated functions. The handler and handler arguments
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to esp_intr_alloc must be NULL, however.
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- In theory, medium priority interrupts could also be handled in this way. For now, ESP-IDF does not support this.
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