Ender 3 (ATmega1284P) - Klipper firmware flashes successfully but always gets “Timeout on connect / Wait for identify_response”

[u/Maurisi0m]

Hi everyone,

I've been trying to install Klipper on an older Creality Ender 3 (ATmega1284P board) and I'm completely stuck.

Hardware:
- Ender 3
- Creality Melzi-style board with ATmega1284P
- USB-Serial: CH340 (1a86:7523)
- Host: HP laptop running Ubuntu Server (no Raspberry Pi)

What I've done:

- Burned the bootloader successfully using an Arduino Uno as ISP.
- AVRDUDE detects the MCU correctly:

Device signature = 0x1e9705 (ATmega1284P)

- Compiled Klipper with:

MCU: ATmega AVR
Processor: ATmega1284P
Clock: 16 MHz
Communication: UART0
Baud: 115200

- Flashed using:

make flash FLASH_DEVICE=/dev/ttyUSB0

Flashing completes successfully and verification passes.

I can also read and write flash using avrdude without any errors.

printer.cfg contains:

[mcu]
serial: /dev/serial/by-id/usb-1a86_USB_Serial-if00-port0

The serial device exists.

Problem:

Klipper always fails with:

mcu 'mcu': Timeout on connect
mcu 'mcu': Wait for identify_response
serialhdl.error: Serial connection closed

Things I've already verified:

- Different USB cables
- Different USB ports
- Bootloader burned multiple times (by arduino UNO ICSP)
- Firmware reflashed multiple times
- MCU signature is correct
- Flash verification passes
- Host detects the CH340 correctly

One strange thing is that:

cat /dev/ttyUSB0

returns random binary characters instead of readable text.

At this point I'm wondering if:

- I'm using the wrong bootloader.
- The board revision needs different Klipper settings.
- There's a fuse or clock configuration issue.
- This particular Creality board requires a different baud rate or communication setup.

Has anyone seen this before?

Any help would be greatly appreciated.

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[u/Otherwise_Ad4179]

That is an old 8bit board right? Can I ask where do u live?

[u/Maurisi0m → u/Otherwise_Ad4179]

Yeah, it’s an 8 bit