defmt-persist-print

A version of defmt-print that prints defmt logs saved by defmt-persist by supporting its framing encoding.

Usage

Use probe-rs-cli to read a dump of persisted logs from the device and then pass them to defmt-persist-print.

1. Install probe-rs-cli:

cargo install probe-rs-cli --force

2. Install this tool via cargo:

cargo install

3. Read persisted logs (example):

export ELF_PATH=/path/to/the/binary.elf
export LOGS_FLASH_BASE_ADDR=08040000
export LOGS_FLASH_SIZE_BYTES=4096
export CHIP_NAME=STM32WB55CGUx
probe-rs-cli dump --chip $CHIP_NAME $LOGS_FLASH_BASE_ADDR $LOGS_FLASH_SIZE_BYTES | defmt-persist-print $ELF_PATH

How It Works

First, the probe-rs-cli produces the following dump of the FLASH memory area where logs were saved:

Addr 0x08040000: 0xefbeedfe
Addr 0x08040004: 0xbebafeca
Addr 0x08040008: 0xfdffecfd

------- >% SNIP %< -------

Addr 0x0804001c: 0xfcfe05fd
Addr 0x08040020: 0xffffffff
Addr 0x08040024: 0xffffffff
Read 10 words in 778.346µs

The dump above is then decoded into binary blob which is then decoded by defmt-persist into defmt frames.

These frames are then displayed as the actual log messages by defmt with the help of data from an ELF firmware binary passed into the tool. The binary contains crucial information about log strings format.

Output example:

────────────────────────────────────────────────────────────────────────────────
 INFO  Starting
└─ ble_quaternions::__cortex_m_rt_main @ src/bin/ble_quaternions.rs:598
 INFO  Running main
└─ ble_quaternions::run_main::task::{{closure}} @ src/bin/ble_quaternions.rs:102
 INFO  Waiting for PMIC
└─ tracksb::pmic::wait_init_pmic::{{closure}} @ src/pmic.rs:267
 INFO  Setting IMU enabled: true
└─ tracksb::pmic::{{impl}}::set_imu_power::{{closure}} @ src/pmic.rs:155
 INFO  Resetting IMU
└─ tracksb::imu::{{impl}}::reset_imu::{{closure}} @ src/imu.rs:127
 INFO  Updating battery level 95%
└─ ble_quaternions::update_battery_level::{{closure}} @ src/bin/ble_quaternions.rs:370
...
────────────────────────────────────────────────────────────────────────────────

Credits

This tool is based on Knurling's defmt-print.

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)

• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.