Possible to flash MMU3 from a Raspberry Pi?  

Yes.

It can be done with the command line but if you're working headless you'll probably find it easier to use VNC.  The flatpack version of PrusaSlicer makes working remotely difficult - so instead download an AppImage from:

  https://github.com/davidk/PrusaSlicer-ARM.AppImage/releases/tag/version_2.9.4

Cheerio,

RE: Possible to flash MMU3 from a Raspberry Pi?

It can be done with the command line

You wouldn't happen to know exactly what command line command does it?  All I need to do is to get it working once, then I can script it.

RE: Possible to flash MMU3 from a Raspberry Pi?

Ok, thanks.  For anyone else interested, here's a script that automates the process, using the stock avrdude:

#!/bin/bash

# Configuration
INITIAL_PORT="/dev/ttyACM0"
BAUD_RATE="57600"
MCU="atmega32u4"
PROGRAMMER="avr109"

# 1. Check if an argument was provided
if [ -z "$1" ]; then
    echo "Usage: $0 <path_to_firmware_file>"
    exit 1
fi

HEX_FILE="$1"

echo "--- MMU3 Remote Flash Tool (Deep Verification) ---"

# 2. File Existence Check
if [ ! -f "$HEX_FILE" ]; then
    echo "Error: File '$HEX_FILE' not found."
    exit 1
fi

# 3. Content Verification (Intel HEX format)
# Validates that lines start with ':' and contain only hex chars/newlines
if ! grep -q "^:[0-9A-Fa-f]\{10,\}" "$HEX_FILE"; then
    echo "Error: File '$HEX_FILE' does not contain valid Intel HEX data."
    echo "This does not look like a valid firmware file."
    exit 1
fi

echo "File verification passed (Valid Intel HEX detected)."

# 4. Dependency Check
if ! command -v avrdude &> /dev/null; then
    echo "Error: 'avrdude' is not installed. Run: sudo apt install avrdude"
    exit 1
fi

# 5. Trigger the bootloader
echo "Sending 1200-baud reset signal to $INITIAL_PORT..."
# Redirecting stderr to /dev/null because stty might complain if the port
# closes instantly, which is actually what we want.
stty -F "$INITIAL_PORT" 1200 2>/dev/null

# 6. Wait for re-enumeration
echo "Waiting 2 seconds for bootloader to appear..."
sleep 2

# 7. Detect the active port 
NEW_PORT=$(ls /dev/ttyACM* 2>/dev/null | head -n 1)

if [ -z "$NEW_PORT" ]; then
    echo "Error: MMU3 not found on /dev/ttyACM* after reset."
    echo "It may have failed to enter bootloader mode."
    exit 1
fi

echo "Found device on $NEW_PORT. Starting upload..."

# 8. Execute Flash
avrdude -v -p "$MCU" -c "$PROGRAMMER" -P "$NEW_PORT" -b "$BAUD_RATE" -D -U flash:w:"$HEX_FILE":i

# 9. Final Result
if [ $? -eq 0 ]; then
    echo "------------------------------------------------"
    echo "SUCCESS: MMU3 firmware updated!"
else
    echo "------------------------------------------------"
    echo "FAILURE: Flash process failed."
    echo "Check if OctoPrint is still connected to the port."
    exit 1
fi

RE: Possible to flash MMU3 from a Raspberry Pi?

I had to update my MMU3 anyway, so I tried it using my Pi5, the standard avrdude package from debian and your script. It worked successfully at the first try. 🙂