IDF Monitor

[中文]

The IDF Monitor tool is a Python program which runs when the make monitor target is invoked in IDF.

It is mainly a serial terminal program which relays serial data to and from the target device’s serial port, but it has some other IDF-specific features.

Interacting With IDF Monitor

  • Ctrl-] will exit the monitor.

  • Ctrl-T Ctrl-H will display a help menu with all other keyboard shortcuts.

  • Any other key apart from Ctrl-] and Ctrl-T is sent through the serial port.

Automatically Decoding Addresses

Any time esp-idf prints a hexadecimal code address of the form 0x4_______, IDF Monitor will use addr2line to look up the source code location and function name.

When an esp-idf app crashes and panics a register dump and backtrace such as this is produced:

Guru Meditation Error of type StoreProhibited occurred on core  0. Exception was unhandled.
Register dump:
PC      : 0x400f360d  PS      : 0x00060330  A0      : 0x800dbf56  A1      : 0x3ffb7e00
A2      : 0x3ffb136c  A3      : 0x00000005  A4      : 0x00000000  A5      : 0x00000000
A6      : 0x00000000  A7      : 0x00000080  A8      : 0x00000000  A9      : 0x3ffb7dd0
A10     : 0x00000003  A11     : 0x00060f23  A12     : 0x00060f20  A13     : 0x3ffba6d0
A14     : 0x00000047  A15     : 0x0000000f  SAR     : 0x00000019  EXCCAUSE: 0x0000001d
EXCVADDR: 0x00000000  LBEG    : 0x4000c46c  LEND    : 0x4000c477  LCOUNT  : 0x00000000

Backtrace: 0x400f360d:0x3ffb7e00 0x400dbf56:0x3ffb7e20 0x400dbf5e:0x3ffb7e40 0x400dbf82:0x3ffb7e60 0x400d071d:0x3ffb7e90

IDF Monitor will augment the dump:

Guru Meditation Error of type StoreProhibited occurred on core  0. Exception was unhandled.
Register dump:
PC      : 0x400f360d  PS      : 0x00060330  A0      : 0x800dbf56  A1      : 0x3ffb7e00
0x400f360d: do_something_to_crash at /home/gus/esp/32/idf/examples/get-started/hello_world/main/./hello_world_main.c:57
(inlined by) inner_dont_crash at /home/gus/esp/32/idf/examples/get-started/hello_world/main/./hello_world_main.c:52
A2      : 0x3ffb136c  A3      : 0x00000005  A4      : 0x00000000  A5      : 0x00000000
A6      : 0x00000000  A7      : 0x00000080  A8      : 0x00000000  A9      : 0x3ffb7dd0
A10     : 0x00000003  A11     : 0x00060f23  A12     : 0x00060f20  A13     : 0x3ffba6d0
A14     : 0x00000047  A15     : 0x0000000f  SAR     : 0x00000019  EXCCAUSE: 0x0000001d
EXCVADDR: 0x00000000  LBEG    : 0x4000c46c  LEND    : 0x4000c477  LCOUNT  : 0x00000000

Backtrace: 0x400f360d:0x3ffb7e00 0x400dbf56:0x3ffb7e20 0x400dbf5e:0x3ffb7e40 0x400dbf82:0x3ffb7e60 0x400d071d:0x3ffb7e90
0x400f360d: do_something_to_crash at /home/gus/esp/32/idf/examples/get-started/hello_world/main/./hello_world_main.c:57
(inlined by) inner_dont_crash at /home/gus/esp/32/idf/examples/get-started/hello_world/main/./hello_world_main.c:52
0x400dbf56: still_dont_crash at /home/gus/esp/32/idf/examples/get-started/hello_world/main/./hello_world_main.c:47
0x400dbf5e: dont_crash at /home/gus/esp/32/idf/examples/get-started/hello_world/main/./hello_world_main.c:42
0x400dbf82: app_main at /home/gus/esp/32/idf/examples/get-started/hello_world/main/./hello_world_main.c:33
0x400d071d: main_task at /home/gus/esp/32/idf/components/esp32/./cpu_start.c:254

Behind the scenes, the command IDF Monitor runs to decode each address is:

xtensa-esp32-elf-addr2line -pfiaC -e build/PROJECT.elf ADDRESS

Launch GDB for GDBStub

By default, if an esp-idf app crashes then the panic handler prints registers and a stack dump as shown above, and then resets.

Optionally, the panic handler can be configured to run a serial “gdb stub” which can communicate with a gdb debugger program and allow memory to be read, variables and stack frames examined, etc. This is not as versatile as JTAG debugging, but no special hardware is required.

To enable the gdbstub, run make menuconfig and set CONFIG_ESP32_PANIC option to Invoke GDBStub.

If this option is enabled and IDF Monitor sees the gdb stub has loaded, it will automatically pause serial monitoring and run GDB with the correct arguments. After GDB exits, the board will be reset via the RTS serial line (if this is connected.)

Behind the scenes, the command IDF Monitor runs is:

xtensa-esp32-elf-gdb -ex "set serial baud BAUD" -ex "target remote PORT" -ex interrupt build/PROJECT.elf

Quick Compile and Flash

The keyboard shortcut Ctrl-T Ctrl-F will pause IDF Monitor, run the make flash target, then resume IDF Monitor. Any changed source files will be recompiled before re-flashing.

The keyboard shortcut Ctrl-T Ctrl-A will pause IDF Monitor, run the make app-flash target, then resume IDF Monitor. This is similar to make flash, but only the main app is compiled and reflashed.

Quick Reset

The keyboard shortcut Ctrl-T Ctrl-R will reset the target board via the RTS line (if it is connected.)

Pause the Application

The keyboard shortcut Ctrl-T Ctrl-P will reset the target into bootloader, so that the board will run nothing. This is useful when you want to wait for another device to startup. Then shortcut Ctrl-T Ctrl-R can be used to restart the application.

Toggle Output Display

Sometimes you may want to stop new output printed to screen, to see the log before. The keyboard shortcut Ctrl-T Ctrl-Y will toggle the display (discard all serial data when the display is off) so that you can stop to see the log, and revert again quickly without quitting the monitor.

Filtering the Output

The IDF monitor can be invoked as make monitor PRINT_FILTER="" with specifying a custom PRINT_FILTER option for filtering outputs. The default value is an empty string which means that everything will be printed. Restrictions on what to print can be specified as a series of <tag>:<log_level> items where <tag> is the tag string and <log_level> is a character from set {N, E, W, I, D, V, *} referring to a level for logging. For example, PRINT_FILTER="tag1:W" will match and print (only) the outputs written with ESP_LOGW("tag1", ...) or at lower verbosity level, i.e. ESP_LOGE("tag1", ...). Not specifying a <log_level> or using * defaults to Verbose level.

Note

The primary logging is set up at compilation time through the logging library. Output filtering by the IDF monitor is only a secondary solution because one cannot filter something which has been disabled at compilation time. The advantage of the secondary filtering is that one can use various filtering options without recompiling the application.

A restriction applies to tags when one wants to use them together with output filtering: they cannot contain spaces, asterisks * and semicolons :.

If the last line of the output is written without an end of line then the output filtering might get confused, i.e. the monitor starts to print the line and only later finds out that the line should have not been written. This is a known issue and can be avoided by always adding an end of line after printing something (especially when no output follows immediately afterwards).

Examples Of Filtering Rules:

  • Asterisk can be used to match any tags. However, specifying PRINT_FILTER="*:I tag1:E" will print for tag1 only errors because the rule for tag1 has a precedence over the rule for *.

  • The default (empty) rule is equivalent to *:V because matching every tag at level Verbose or lower means matching everything.

  • Rule "tag1:W tag1:E" is equivalent to "tag1:E" because any consequent occurrence of the same tag name overwrites the previous one.

  • Rule "tag1:I tag2:W" will print only tag1 at verbosity level Info or lower and tag2 at verbosity level Warning or lower.

  • Rule "tag1:I tag2:W tag3:N" is essentially equivalent to the previous one because tag3:N specifies that tag3 should not be printed.

  • tag3:N in rule "tag1:I tag2:W tag3:N *:V" is more meaningful because in this context the result will be that tag3 will not be printed, tag1 and tag2 will be at the specified (or lower) verbosity level and everything else will be printed by default.

  • "*:N" will suppress all outputs even prints made by something else than the logging functions, e.g. printf. For printing those outputs one need to use *:E or higher verbosity level.

  • Rules "tag1:V", "tag1:v", "tag1:", "tag1:*" and "tag1" are all equivalent ones.

A More Complex Filtering Example

The following log snippet was acquired using make monitor:

load:0x40078000,len:13564
entry 0x40078d4c
E (31) esp_image: image at 0x30000 has invalid magic byte
W (31) esp_image: image at 0x30000 has invalid SPI mode 255
E (39) boot: Factory app partition is not bootable
I (568) cpu_start: Pro cpu up.
I (569) heap_init: Initializing. RAM available for dynamic allocation:
I (603) cpu_start: Pro cpu start user code
D (309) light_driver: [light_init, 74]:status: 1, mode: 2
D (318) vfs: esp_vfs_register_fd_range is successful for range <54; 64) and VFS ID 1
I (328) wifi: wifi driver task: 3ffdbf84, prio:23, stack:4096, core=0

The captured output for make monitor PRINT_FILTER="wifi esp_image:E light_driver:I" is the following:

E (31) esp_image: image at 0x30000 has invalid magic byte
I (328) wifi: wifi driver task: 3ffdbf84, prio:23, stack:4096, core=0

make monitor PRINT_FILTER="light_driver:D esp_image:N boot:N cpu_start:N vfs:N wifi:N *:V" gives the following output:

load:0x40078000,len:13564
entry 0x40078d4c
I (569) heap_init: Initializing. RAM available for dynamic allocation:
D (309) light_driver: [light_init, 74]:status: 1, mode: 2

Simple Monitor

Earlier versions of ESP-IDF used the pySerial command line program miniterm as a serial console program.

This program can still be run, via make simple_monitor.

IDF Monitor is based on miniterm and shares the same basic keyboard shortcuts.

Known Issues with IDF Monitor

Issues Observed on Windows

  • If you are using the supported Windows environment and receive the error “winpty: command not found” then run pacman -S winpty to fix.

  • Arrow keys and some other special keys in gdb don’t work, due to Windows Console limitations.

  • Occasionally when “make” exits, it may stall for up to 30 seconds before idf_monitor resumes.

  • Occasionally when “gdb” is run, it may stall for a short time before it begins communicating with the gdbstub.