espflash vs. probe-rs

There are implication to selecting the logging strategy for embedded ESP32 Rust projects. The strategies are not clearly defined, or documented. It's kind of like a Wild West.

Belowm the author places them in four categories.

The repo examines the compatibility of each of the strategies with the ST.com VL53L5CX time-of-flight sensor.

Why VL53L5CX??? Because the sensor('s use of I2C bus) has some compatibility issues with probe-rs, which lead the author down this 🐰🕳️ to begin with.

Four logging strategies

espflash-println

Uses println! macros; run using espflash --monitor; depends on: esp-println

espflash-log

Uses {debug|info|warn|...}! macros; run using espflash --monitor; depends on: log, esp-println

espflash-defmt

Uses {debug|info|warn|...}! macros; run using espflash monitor --log-format defmt; depends on: defmt, esp-println

probe_rs-defmt

Uses {debug|info|warn|...}! macros; run using probe-rs; depends on: defmt, defmt-rtt

Requirements

• ESP32-C3 devkit
• SATEL evaluation board
• patience!

Wiring

ESP32-C3 pins	Satel	other/comments
GND	1. GND
3v3	2. 3v3
5V	3. 5V
GPIO6	4. PWR_EN	Alternatively, via ~47kΩ to +3v3
--	5. --	pulled up by Satel
GPIO4	6. SCL
GPIO5	7. SDA
--	8. --
--	9. --

For ESP32-C6 pins, see the source.

Run

Contents of the main branch are set up for targetting ESP32-C3.

espflash-println: esp-println and println!

• connect the devkit to either USB/UART or USB/JTAG port

•  run

  $ cargo run --release --features=esp-hal-next --example basic
  

Sample output:

[...]
Print data no : 23
Zone : 0, Status : 5, Distance : 1741 mm
Zone : 1, Status : 5, Distance : 1785 mm
Zone : 2, Status : 4, Distance : 1785 mm
Zone : 3, Status : 5, Distance : 1850 mm
Zone : 4, Status : 5, Distance : 1748 mm
Zone : 5, Status : 4, Distance : 1762 mm
[...]

espflash-log: esp-println and {debug|info|warn|...}!

• connect the devkit to either USB/UART or USB/JTAG port

•  run

  $ cargo run --release --no-default-features --features=esp-hal-next,espflash-log --example basic
  

Sample output:

[...]
INFO - Print data no : 4
INFO - Zone : 0, Status : 5, Distance : 1777 mm
INFO - Zone : 1, Status : 5, Distance : 1776 mm
INFO - Zone : 2, Status : 5, Distance : 1776 mm
INFO - Zone : 3, Status : 5, Distance : 1778 mm
INFO - Zone : 4, Status : 5, Distance : 1782 mm
INFO - Zone : 5, Status : 5, Distance : 1778 mm
INFO - Zone : 6, Status : 5, Distance : 1780 mm
[...]

Note: Coloring is by the line, e.g. all INFO lines are green.

Note: The ESP_LOG env.var. in .cargo/config.toml should now be usable for setting the logging level (but this didn't work for the author). tbd.

espflash-defmt

• connect the devkit to either USB/UART or USB/JTAG port

•  build

  $ cargo build --release --no-default-features --features=esp-hal-next,espflash-defmt --example basic
  

• run

   $ espflash flash --log-format defmt --monitor target/riscv32imc-unknown-none-elf/release/examples/basic
  

Output:

[...]
9.304684 INFO Zone : 0, Status : 4, Distance : 1796 mm
9.304828 INFO Zone : 1, Status : 4, Distance : 1777 mm
9.304955 INFO Zone : 2, Status : 255, Distance : 83 mm
9.305079 INFO Zone : 3, Status : 255, Distance : 82 mm
9.305206 INFO Zone : 4, Status : 4, Distance : 1781 mm
9.305332 INFO Zone : 5, Status : 4, Distance : 1774 mm
9.305461 INFO Zone : 6, Status : 255, Distance : 90 mm
9.305580 INFO Zone : 7, Status : 255, Distance : 90 mm
[...]

We get time stamps, log levels (colored only on the INFO, not the whole lines).

probe_rs-defmt

• connect the devkit to the USB/JTAG port

•  build

  $ cargo build --release --no-default-features --features=esp-hal-next,probe_rs-defmt --example basic
  

•  run

  $ probe-rs run "--log-format={{t:dimmed} [{L:bold}]} {s}  {{c} {ff}:{l:1}%dimmed}" target/riscv32imc-unknown-none-elf/release/examples/basic
  

Running fails with:

Finished in 5.05s
0.223258 [INFO ] SATEL board powered off and on again.  basic examples/fmt.rs:150
0.227887 [INFO ] alive = 0 1  basic examples/fmt.rs:150
0.490474 [ERROR] ====================== PANIC ======================  esp_backtrace src/lib.rs:25
0.490497 [ERROR] panicked at examples/basic.rs:270:14  esp_backtrace src/lib.rs:25
0.490601 [ERROR] Backtrace:  esp_backtrace src/lib.rs:25
0.490671 [ERROR] 0x42000c8e  esp_backtrace src/lib.rs:25

Note: probe-rs provides nicer coloring than espflash, and the log format can be fine tuned.

Unfortunately, probe-rs (0.26.0) does not work with esp-hal I2C access (long story, documented elsewhere; RTT stopping the MCU core disturbs I2C traffic).

Same with ESP32-C6...?

If you wish to try on another MCU:

$ cat .cargo/config.toml | sed -E 's/riscv32im[a]?c/riscv32imac/g' > .tmp
$ mv .tmp .cargo/config.toml

$ cat Cargo.toml | sed -E 's/"esp32c[[:digit:]]"/"esp32c6"/g' > .tmp
$ mv .tmp Cargo.toml

Summary

At the moment, the VL53L5 device is usable only with a narrow combination of devkits, logging choices, and MCUs:

devkit	esp-hal	espflash-println	espflash-log	espflash-defmt	probe_rs-defmt
ESP32-C3-DevkitC-02
	main (latest; moving target)	✅	✅	✅	❌
ESP32-C6-Devkit-M1
	main (latest; moving target)	❌ scanning does not start; error 255			❌
	0.23.1	❌ as above			❌ Does not start; no output
	0.23.0	❌ as above			❌ Does not start; no output

Next steps

• Repeat the ESP32-C6 results with another devkit / breadboard.