avrdude setup on the Raspberry Pi

• Install avrdude: sudo apt install avrdude

• Copy the default config to my home directory: cp /etc/avrdude.conf ~/avrdude_gpio.conf

• Edit the new file: emacs ~/avrdude_gpio.conf

• Change the baudrate for the 'linuxspi' section to 115200

  • Find the linuxspi section: press ctrl-s -> type 'linuxspi' -> hit enter

  • Change the baudrate value:

    programmer
      id = "linuxspi";
      desc = "Use Linux SPI device in /dev/spidev*";
      type = "linuxspi";
      reset = 25;
      baudrate = 115200;
    

• Add a new config at the bottom of the file. This will allow use of the GPIO pins:

  programmer
    id = "pi_1";
    desc = "Use the Linux sysfs interface to bitbang GPIO lines";
    type = "linuxgpio";
    reset = 17;
    sck = 24;
    mosi = 23;
    miso = 18;
  

• Save and close: press ctrl-x, ctrl-s, ctrl-x, ctrl-c

The bootloader binary

Actually finding the bootloader binary proved difficult. Most tutorials mention using the Arduino IDE, setting the board the sanguino and then flashing it directly. Recent versions of Arduino don't include the sanguino board configurations by default.

There are work arounds, but I've already setup avrdude to do the actual flashing and I just need the binary file. Multiple guides mention this too: just use the Arduino IDE to download the files for them and then copy them elsewhere. I don't need the IDE for anything else, so no need to install it.

Instead, just download the binary bootloader directly from the git repository directly to the Raspberry Pi:

wget https://raw.githubusercontent.com/Lauszus/Sanguino/master/bootloaders/optiboot/optiboot_atmega1284p.hex

* - SPI pins
W - white connectors
G - green connectors
B - black screen connector
U - USB port

+------------------------------------------+
|   W W W W W W W W W W W W   G G G G G G
| BB
| BB
| BB
| BB
| BB
| **
| **
| **
| **
|
|
| UUU
| UUU
|

Printer connections

              ++
              ++
(display port)++
              ++
              ++

(ground) GND  OO Reset (GPIO17)
(GPIO23) MOSI OO SCK   (GPIO24)
(3.3V)   VCC  OO MISO  (GPIO18)

GPIO connections

(VCC)     3.3v OO
               OO
               OO ground (GND)
               OO
               OO
(Reset) GPIO17 OO GPIO18 (MISO)
               OO
               OO GPIO23 (MOSI)
               OO GPIO24 (SCK)
               OO
               OO
               OO
               OO
               OO
               OO
               OO
               OO
               OO
               OO
               OO

sudo avrdude -p atmega1284p -C ~/avrdude_gpio.conf -c pi_1 -v

Flashing the Bootloader

At this point the hard part is over, just flash the bootloader (run in the folder containing the bootloader binary):

sudo avrdude -p atmega1284p -C ~/avrdude_gpio.conf -c pi_1 -v -U flash:w:optiboot_atmega1284p.hex:i

Once that's completed without error, the bootloader has been flashed and it won't need to be done again!

But, at this point, turning the printer on will only result in a blank screen. The firmware was erased when the bootloader was flashed.

Getting the Sources

Just get the latest release. You'll also need the configuration files linked here.

Unzip the sources and the configuration files to separate folders. In the configuration folder, go to config/examples/Creality/Ender-3 Pro/ (not Ender-3 Pro v1.5 - that's for the 4.2.x board) and copy all of the files there to the Marlin folder of the sources. This will overwrite a couple of files.

VSCode and PlatformIO

Again, many of the guides online suggest using Arduino IDE. This is probably convenient if you are connected directly to the printer, but again, I have the Raspberry Pi setup to flash the firmware.

I also had issues compiling Marlin with Arduino IDE. I found the VSCode and PlatformIO approach to be easier, even if not as well known or documented.

It does require some setup:

• Install Visual Studio Code and open it
• Install the PlatformIO IDE extension - Click on the extensions button on the left side bar - Search for 'PlatformIO IDE' and select it - Click Install
• Open the Marlin project - Click the PlatformIO button on the left side bar - In the tree view select Quick Access -> PIO Home -> Open - In the window that opens, click 'Open Project' - Select the root source folder (it should contain a file named platformio.ini)

Build Marlin

Build by selecting Terminal->Run Build Task.

I got an error the first few times:

This is because the 8bit boards have a fairly limited amount of storage space for the firmware: 124Kb! Each feature and instruction supported takes up more room, and I enabled a few extras in mine. I have to disable something to make room.

Some people disable the boot screens to save space, but I'm not quite that desperate, I just need a bit. According to a few guides I've read, ARC_SUPPORT` isn't something that 3D printers normally use, so I disabled that by commenting out ``#define ARC_SUPPORT in Configuration_adv.h.

Build again and success! It's close, but it's just small enough:

Flashing the Firmware

Finally, time to flash the firmware. Connect the printer to the Raspberry Pi using the USB cable and turn the printer on. If this is the first time flashing firmware since installing the bootloader, the screen will just be blank. That is OK.

Now, to find the compiled firmware binary. Look at the last few lines of the build output, something like:

Linking .pio\build\sanguino1284p\firmware.elf
Checking size .pio\build\sanguino1284p\firmware.elf
Building .pio\build\sanguino1284p\firmware.hex
Advanced Memory Usage is available via "PlatformIO Home > Project Inspect"
RAM:   [===       ]  28.0% (used 4580 bytes from 16384 bytes)
Flash: [==========]  98.3% (used 124878 bytes from 126976 bytes)

Copy the file mentioned in the line that starts with 'Building' (the filename should be firmware.hex) to the Raspberry Pi. I used the VNC viewer's file transfer function.

Then, run avrdude again, in the folder containing the firmware.hex file:

sudo avrdude -p atmega1284p -c arduino -P /dev/ttyUSB0 -b 115200 -U flash:w:firmware.hex:i

This takes a bit longer than the bootloader, so be patient. When complete, the printer should boot up, first showing the Ender Dragon, then the Marlin screen and finally the main screen:

Success!