esp32c6 not booting since commit d118250c5cf163426d68e1335323e9804c4b1d9e

[nponsard]

Bug description

I've tried flashing multiple examples from the main branch like embassy_hello_world, embassy_hello_world_defmt and access_point. None of seem to work, the only logs I get are from the bootloader (written in green) and after some time the command stops with

Error:   × Broken pipe

[2025-12-09T14:26:05Z ERROR xtask::commands::run] Failed to run example: Failed to execute cargo subcommand `cargo run --manifest-path /home/nponsard/git/esp-hal/examples/async/embassy_hello_world_defmt/Cargo.toml --config /home/nponsard/git/esp-hal/examples/async/embassy_hello_world_defmt/.cargo/config.toml --target=riscv32imac-unknown-none-elf --features=esp32c6 --release`

I tried with two esp32c6 boards, one FireBeetle 2 esp32-c6 v1.0 and one XIAO esp32c6.

Using git bisect I found that the first bad commit is d118250

To Reproduce

1. check out commit 10025b6
2. run cargo xtask run example embassy_hello_world_defmt --chip=esp32c6 or cargo xtask run example access_point --chip=esp32c6
3. notice that there is no output from the program.

Expected behavior

Examples booting and for the hello-world examples, displaying hello world in the console.

Environment

• Target device: esp32c6 (revision v0.1)
• Crate name and version: esp-hal commit d118250 to 10025b6 (main at time of posting)
• espflash 3.3.0
• rust toolchain v1.91.1

[bugadani]

Issue title says C2, are you having issues with that one, too?

[bugadani]

Can you provide the output of espflash board-info for all affected boards, please?

[nponsard]

Issue title says C2, are you having issues with that one, too?

Sorry that was a mistake, I only tried on esp32c6

[nponsard]

XIAO:

[2025-12-09T14:48:05Z INFO ] Serial port: '/dev/ttyACM0'
[2025-12-09T14:48:05Z INFO ] Connecting...
[2025-12-09T14:48:05Z INFO ] Using flash stub
Chip type:         esp32c6 (revision v0.1)
Crystal frequency: 40 MHz
Flash size:        4MB
Features:          WiFi 6, BT 5
MAC address:       

FireBeetle:

[2025-12-09T14:48:41Z INFO ] Serial port: '/dev/ttyACM0'
[2025-12-09T14:48:41Z INFO ] Connecting...
[2025-12-09T14:48:41Z INFO ] Using flash stub
Chip type:         esp32c6 (revision v0.1)
Crystal frequency: 40 MHz
Flash size:        4MB
Features:          WiFi 6, BT 5
MAC address:       

[bugadani]

Thank you! One more thing: have you tried espflash 4.x?

[nponsard]

Just tried with espflash v4.2.0 on both boards with example embassy_hello_world and embassy_hello_world_defmt on commit 10025b6 .

Same behavior : only the bootloader has output :

[2025-12-09T14:53:53Z INFO ] Flashing has completed!
Commands:
    CTRL+R    Reset chip
    CTRL+C    Exit

ESP-ROM:esp32c6-20220919
Build:Sep 19 2022
rst:0x15 (USB_UART_HPSYS),boot:0x7f (SPI_FAST_FLASH_BOOT)
Saved PC:0x4080082e
0x4080082e - core::slice::memchr::memchr_aligned::runtime
    at /rustc/ed61e7d7e242494fb7057f2657300d9e77bb4fcb/library/core/src/slice/memchr.rs:81
SPIWP:0xee
mode:DIO, clock div:2
load:0x40875720,len:0x16b8
load:0x4086c110,len:0xe90
load:0x4086e610,len:0x3054
entry 0x4086c11a
I (23) boot: ESP-IDF v5.4.1-426-g3ad36321ea 2nd stage bootloader
I (23) boot: compile time Apr 29 2025 15:14:17
I (24) boot: chip revision: v0.1
I (24) boot: efuse block revision: v0.3
I (28) boot.esp32c6: SPI Speed      : 80MHz
I (32) boot.esp32c6: SPI Mode       : DIO
I (35) boot.esp32c6: SPI Flash Size : 4MB
I (39) boot: Enabling RNG early entropy source...
I (44) boot: Partition Table:
I (46) boot: ## Label            Usage          Type ST Offset   Length
I (53) boot:  0 nvs              WiFi data        01 02 00009000 00006000
I (59) boot:  1 phy_init         RF data          01 01 0000f000 00001000
I (66) boot:  2 factory          factory app      00 00 00010000 003f0000
I (72) boot: End of partition table
I (76) esp_image: segment 0: paddr=00010020 vaddr=42000020 size=03984h ( 14724) map
I (86) esp_image: segment 1: paddr=000139ac vaddr=40800000 size=00014h (    20) load
I (90) esp_image: segment 2: paddr=000139c8 vaddr=420039c8 size=09978h ( 39288) map
I (105) esp_image: segment 3: paddr=0001d348 vaddr=40800014 size=029a0h ( 10656) load
I (108) esp_image: segment 4: paddr=0001fcf0 vaddr=408029b8 size=006f0h (  1776) load
I (114) boot: Loaded app from partition at offset 0x10000
I (118) boot: Disabling RNG early entropy source...
Error:   × Broken pipe

[2025-12-09T14:54:02Z ERROR xtask::commands::run] Failed to run example: Failed to execute cargo subcommand `cargo run --manifest-path /home/nponsard/git/esp-hal/examples/async/embassy_hello_world/Cargo.toml --config /home/nponsard/git/esp-hal/examples/async/embassy_hello_world/.cargo/config.toml --target=riscv32imac-unknown-none-elf --features=esp32c6 --release`

[nponsard]

Running embassy_hello_world_defmt setting DEFMT_LOG = "trace" I get some output from the program, the last lines are

[DEBUG] Reset Uart1 (esp_hal esp-hal/src/system.rs:197)
[DEBUG] Enable Uart1 false (esp_hal esp-hal/src/system.rs:189)
[DEBUG] Reset Uhci0 (esp_hal esp-hal/src/system.rs:197)
[DEBUG] Enable Uhci0 false (esp_hal esp-hal/src/system.rs:189)

[bugadani]

Thanks for the info. Unfortunately this means that I don't have a good way to reproduce your issue - my C6 is v0.0, and the one in the HIL tester is v0.2 and it seems that at least tests run fine on both of them (and my board runs the examples just fine using either of the USB ports).

Just to see if we may have a false negative in CI, can you try running cargo xtask run tests esp32c6 --tests esp_radio for example?

[nponsard]

This seems to fail on my boards:

$ cargo xtask run tests esp32c6 --test esp_radio
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.10s
     Running `target/debug/xtask run tests esp32c6 --test esp_radio`
[2025-12-09T15:02:49Z INFO  xtask] Building command: Run 'src/bin/esp_radio.rs' for 'esp32c6'
[2025-12-09T15:02:49Z INFO  xtask]   Features:      embassy, esp-alloc, esp-radio, esp-radio/ble, esp-radio/unstable, esp-radio/wifi, unstable
[2025-12-09T15:02:49Z INFO  xtask]   Configuration: has_wifi_ble
[2025-12-09T15:02:49Z WARN  xtask::cargo] You don't have cargo batch installed. Falling back to cargo.
[2025-12-09T15:02:49Z WARN  xtask::cargo] You should really install cargo-batch.
[2025-12-09T15:02:49Z WARN  xtask::cargo] cargo install --git https://github.com/embassy-rs/cargo-batch cargo --bin cargo-batch --locked
Command: cargo run --manifest-path /home/nponsard/git/esp-hal/hil-test/Cargo.toml --config /home/nponsard/git/esp-hal/hil-test/.cargo/config.toml --target=riscv32imac-unknown-none-elf --features=embassy,esp-alloc,esp-radio,esp-radio/ble,esp-radio/unstable,esp-radio/wifi,unstable,esp32c6 --bin=esp_radio --release
    Updating crates.io index
    Finished `release` profile [optimized + debuginfo] target(s) in 0.52s
     Running `probe-rs run --preverify target/riscv32imac-unknown-none-elf/release/esp_radio`
      Erasing ✔ 100% [####################]   1.12 MiB @ 267.35 KiB/s (took 4s)
  Programming ✔ 100% [####################] 477.44 KiB @  81.30 KiB/s (took 6s)                                                                                                                                                                                                      Finished in 10.45s
Frame 0: <unknown function @ 0x40022bc4> @ 0x40022bc4
Error: The target did not respond with test list until timeout.
Error: Failed tests: [
    "esp_radio_has_wifi_ble",
]

[bugadani]

Hmm that's not the error I've expected, your probe-rs may be a bit too old. Anyway thanks for the info, I'll investigate.