Cannot connect to esp32s3 without `--no-stub`

[skibon02]

Information

Board: YD-ESP32-23 (https://github.com/rtek1000/YD-ESP32-23?tab=readme-ov-file)
Connection: both type-c ports were tested with the same problem

Problem

Running esptool.py --port /dev/ttyACM1 flash_id or esptool.py --port /dev/ttyACM1 chip_id works fine, but if i use espflash board-info --port /dev/ttyACM1 or any other espflash subcommands i got an error:

[2025-06-30T14:50:34Z INFO ] Serial port: '/dev/ttyACM1'
[2025-06-30T14:50:34Z INFO ] Connecting...
[2025-06-30T14:50:35Z INFO ] Using flash stub
Error: espflash::timeout

  × Error while connecting to device
  ╰─▶ Timeout while running command

But when I add flag --no-stub, all commands work and communicate with the board

espflash board-info --port /dev/ttyACM1 --no-stub
[2025-06-30T14:55:56Z INFO ] Serial port: '/dev/ttyACM1'
[2025-06-30T14:55:56Z INFO ] Connecting...
Chip type:         esp32s3 (revision v0.1)
Crystal frequency: 40 MHz
Flash size:        16MB
Features:          WiFi, BLE
MAC address:       34:85:18:93:52:e8

Other information

Communication dump during espflash command execution:

Communication dump during espflash command execution (with --no-stub):

[bugadani]

I can understand that the UART port doesn't work given it's a USB-UART bridge we don't test for, but the direct USB connection should just work. What's the output you see using that?

[skibon02]

Well, when I monitor D+ and D- ports I see constant communication even when espflash is not running, so it is hard to catch something usefull, and probably it's too much low-level

Maybe i can re-run espflash with extended logging information?

[bugadani]

I meant what does espflash tell you?

[skibon02]

It is the same:

$ espflash board-info
[2025-06-30T16:24:54Z INFO ] Serial port: '/dev/ttyACM1'
[2025-06-30T16:24:54Z INFO ] Connecting...
[2025-06-30T16:24:54Z INFO ] Using flash stub
Error: espflash::timeout

  × Error while connecting to device
  ╰─▶ Timeout while running command


$ espflash board-info --no-stub
[2025-06-30T16:25:21Z INFO ] Serial port: '/dev/ttyACM1'
[2025-06-30T16:25:21Z INFO ] Connecting...
Chip type:         esp32s3 (revision v0.1)
Crystal frequency: 40 MHz
Flash size:        16MB
Features:          WiFi, BLE
MAC address:       34:85:18:93:52:e8

lsusb:
Bus 001 Device 090: ID 303a:1001 Espressif USB JTAG/serial debug unit

[SergioGasquez]

What espflash version are you using?

[skibon02]

$ espflash --version
espflash 3.3.0

[SergioGasquez]

$ espflash --version
espflash 3.3.0

Try using espflash@main : cargo install espflash --git https://github.com/esp-rs/espflash

[skibon02]

Now it works fine on v4.0.0-dev:

$ espflash board-info
[2025-07-01T08:43:09Z INFO ] Serial port: '/dev/ttyACM0'
[2025-07-01T08:43:09Z INFO ] Connecting...
[2025-07-01T08:43:09Z INFO ] Using flash stub
[2025-07-01T08:43:09Z WARN ] Could not detect flash size (FlashID=0x00, SizeID=0x00), defaulting to 4MB
Chip type:         esp32s3 (revision v0.1)
Crystal frequency: 40 MHz
Flash size:        4MB
Features:          WiFi, BLE, Embedded Flash
MAC address:       34:85:18:93:52:e8

Security Information:
=====================
Flags: 0x00000680 (11010000000)
Key Purposes: [4, 0, 0, 0, 0, 0, 12]
Chip ID: 9
API Version: 0
Secure Boot: Disabled
Flash Encryption: Disabled
SPI Boot Crypt Count (SPI_BOOT_CRYPT_CNT): 0x3
Dcache in UART download mode: Disabled
Icache in UART download mode: Disabled
JTAG: Permanently Disabled

And serial port also gives the same output (also works)

But flash size now cannot be detected

[SergioGasquez]

We just created #917 to fix this issue! Thanks for reporting it!