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Fork of MarlinFW for use with Monoprice Mini Delta
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Increasing MAXTEMP to 110 for 10A power supplies
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MPMD_3dPrinter Increasing MAXTEMP to 110 for 10A power supplies Aug 2, 2018
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firmware binaries Increasing MAXTEMP to 110 for 10A power supplies Aug 2, 2018
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.gitignore removing unnecessary files Jul 25, 2018 First functional version Sep 27, 2016 Update Aug 2, 2018

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This is a port of Marlin4ST to work with the Monoprice Mini Delta 3D Printer. Marlin4ST itself is based off of MarlinFW version 1.1.0-RC7. Much of this work was necessary to accommodate the less powerful STM32F070CBT microprocessor used in the Monoprice mini delta as well as supporting the specific hardware of thise machine. The motivation for this project was to correct some of the issues with the stock firmware of the printer, most notably the slow communication speed over USB, the inconsistent heater controls, disablement of the some of the safety features, and some of the delta calibrations. The stock firmware is closed-source although it seems to be based off of Marlin, and as as result there's now way of confirming there are no hidden bugs or issues. That said, this is development firmware that has been tested only handful of times by me on two printers. Relevant Marlin safety features have been turned on, but there is no guarantee it is bug free.
USE AT YOUR OWN RISK! 3d printers have been known to fail and cause fires while unattended. I cannot be responsible for any failures as a result of using this software, although unlikely, Monoprice may use this as an excuse to void your warranty if you brick your printer (this is extremely unlikely).

Please see the Wiki for more information on installation, calibration, and other differences specific to this firmware

The stock power supply cannot power both heaters on at the same time, so a special firmware has been created to prevent this situation to allow use of the stock power supply. If you have upgraded to a 10A power supply, use the "firmware_10ALimit.bin" file to allow faster heating and potentially a higher max bed temperature. Otherwise, use the "firmware_5ALimit.bin" file, which should still heat the bed faster, but will still respect the 5A limit of the power supply

Changes from stock monoprice firmware

  • Mesh bed leveling ignores the P0-5 / C parameters that the stock firmware uses. Instead, calling G29 will run a mesh leveling grid over a 7x7 area between -45 to 45mm on the X and Y axes in 15mm increments. Points outside the probeable radius on the print bed will be extrapolated based on probed values. This mesh grid is persistent, and saved/loaded by M500/M501.

New 1.2.2 Changed the behavior of G29, now runs a single point probe to adjust delta height and detect misconfigured steps per mm settings before beginning the normal mesh probe. Behavior of G29 is now as follows:

G29 P0: Only runs the single point delta height probe to adjust for height variances in your build platform or nozzle length. This should replace G29 inside of your g-code and to be run on every print. Does not run the Mesh Bed Leveling Probe

G29 P1: Skips the single point delta height probe and directly runs the Mesh Bed Leveling Probe. This is equivalent to what G29 used to do prior to 1.2.2. This means that delta height errors will be dirctly accounted for in the mesh instead of changing the M665 H parameter

G29 or G29 P2: Runs the single point delta height probe followed by the Mesh Bed Leveling Probe. Because the delta height is adjusted first, the center point of the mesh should be zero'ed out or close to it. If you have old Mesh bed leveling data, you will likely need to adjust your saved values since they will no longer be centered about zero

This means that you should probably not run G29 on startup for every print. Instead, your startup g-code only needs a G28 command at the top and the restored mesh grid should take care of the rest. If you find the initial height is off, then you should adjust the M665 H parameter manually to compensate. The Z parameter for G29 is still valid, but the better way is to use the M851 Z<probe offset> command to compensate for the switch travel of the bed. On my printer I use a value around -0.5mm. YMMV

  • Mesh bed leveling points can be retrieved and edited directly using the M421 command. This is extended by the standard Marlin g-code in the following ways:

    M421 <no parameters> : displays the current mesh

    M421 C : clears the current mesh

    M421 E : re-extrapolates the non-probeable points on the mesh using the actual probe points. fixed in 1.2.2, E now clears these points for youIt is required that you set all of these points to 0.0 manually

    M421 I<X Index> J<Y Index> Z<Value> sets the mesh value at I,J to the Z value

    M421 I<X Index> J<Y Index> Q<Offset> adjusts the mesh value at I,J up or down by Q offset

    Editing of the mesh bed level is required to account for some of the peculiarities of this printer and non-linearities of the bed leveling switches. I strongly recommend doing a paper test at each of the probe points to verify the switch values. In some instances (especially opposite the delta towers) the variation can be as much as 0.2-0.3mm which can throw off the first layer on large prints.

  • added support for M48 for bed probe repeatability

  • M665 delta parameters now includes parameters for adjusting delta height (the distance from the Zmax home position to the bed, the Zmin position in mm), individual rod length (X,Y,Z: adjustments are added to the nominal length in mm), individual tower angles (A,B,C: adjustments to the tower angles in degrees, sum of all three should be 0). New in 1.2.2, now can adjust individual tower radius adjust with D,E,F, units are mm's added or subracted to the nominal radius

How to load the Firmware on a stock printer?

The binary of the Marlin4MPMD firmware is found under firmware binaries\firmware.bin. Also in this folder is the two stock firmwares as provided by, these can be re-loaded at any time by the following instructions. To load the binary onto your printer:

  • Follow the guide in the wiki for correctly formatting and troubleshooting your SD card. Test that you can flash the stock firmware first before installing Marlin4MPMD, if you have not formatted your card correctly you can render your printer inoperable until you have formatted it correctly
  • Further details for installation are available on the wiki
  • Rename the appropriate firmware to firmware.bin, Owners of newer printers should use the v43+ firmware files to set correct default steps per mm copy onto the SD card that came with your printer (or any appropriate FAT32 formatted microSD card. Not all cards are compatible, see the wiki for more details).
  • Also copy the fcupdate.flg file as well
  • Eject the SD card safely from your computer.
  • Power off your Monoprice Mini Delta Printer
  • Insert the SD card into your printer and apply power
  • The multi-function LED should blink white a number of times while it is flashing the new firmware. Then the LED should turn off, and your printer should appear in device manager in Windows as a STMicroelectronics Virtual COM Port (See windows drivers for more information) and as something like /dev/ttyACM0 in Linux.
  • Eject the SD card or issue M30 firmware.bin to prevent re-flashing the firmware everytime your printer powers up. Power cycle your printer.
  • If the light starts blinking white again after some time then the firmware did not flash properly and you will likely need to re-format your SD card and try again. Start with one of the stock firmwares first to confirm that the SD card is formatted properly

How to interface with the updater Marlin4MPMD firmware?

On windows you will need to install the STMicro Virtual COM Port driver found in the windows driver folder. There's a .zip file containing the appropriate drivers. On Linux and Mac the Virtual COM port driver should be installed by default, you should see the serial interface under /dev. Fire up your favorite g-code loading software (Pronterface and Octoprint are confirmed working, Cura seems to work, although I have had some issues with the printer freezing so it is not recommended). Click the Connect button, the terminal window should print: start

Printer is now online.


echo: Last Updated: 2018-07-25 00:00 | Author: (MCheah, MPMD)

Compiled: Jul 31 2018

Issue G28 from the terminal window to make sure that communication is working correctly.

Calibration settings from stock firmware should be directly applicable from the stock firmware, so it is advised to write down the M503 results before re-flashing the firmware. You may need to adjust M92, M666 and M665 for your specific printer. The M301/M304 PID settings are not directly comparable to the stock firmware, but the default values should work fairly nicely.

Current known Limitations:

There are a number of stock features that have not been implemented. They all should be possible, I just haven't bothered implementing them as this was more of a proof of concept than anything.

  • EEPROM support is implemented by saving to M_CFG.G on the SD card, this implies that the SD card is present when executing M500 or M501. Since M501 effectively just executes a G-code script, this means that it cannot be executed inside of another g-code file. Therefore you will need to trigger M501 on connection through octoprint or manually run it every time you power on.
  • Only one G29 calibration pattern of a 7x7 mesh is supported at the moment. This version allows direct editing and saving of the mesh grid, but it's currently hard-coded to a 7x7 grid as it's likely that you will not actually want to run this before every print. fixed in 1.2.2. Call G29 P0 in your g-codeAs a result, it is not able to adjust for changes in delta height without re-running a full mesh calibration, so if you need to finetune the delta height, use the M665 H parameter.
  • LCD GUI browsing of SD card folders isn't supported, all g-code must be stored in the root directory
  • SOME wifi functionality may be available given that you have already set up the IP address previously, but loading g-code or running arbitrary functions over WIFI are not supported. If you're reading this, I'm going to guess that you're already using something like octoprint already


Installation of the firmware uses the stock bootloader to replace the application on the printer. This is perfectly safe and reversible, but if you have issues, you should first check that your SD card formatted correctly. The stock firmware will read both FAT16 and FAT32 partitions, but the bootloader only recognizes FAT32 partitions. See the wiki for more details. Make sure that you have properly formatted the SD card as FAT32 with a 512 byte allocation size. See for more info.

After verifying the partition, copy over one of the stock firmwares to the SD card. If these files do not flash correctly, then you will not be able to install Marlin4MPMD, verify that you can re-flash the stock firmware first.

If the stock firmware can be flashed correctly, then rename one of the appropriate Marlin4MPMD firmware files (depending on which power supply you have) and try installing by SD. The white LED should flash for several seconds and then turn off indicating the new firmware is loaded. If you see flashing red and purple at any time, then a hard error has occurred and the printer should be reset. Green lights are also normal, this means the printer is ready to connect over USB. If you experience problems, please open a github issue and I will try to help.

How to build the FW?

In order to recompile the program , you must do the following :

Open OpenSTM32 (SW4STM32) toolchain (you can download installer for your OS here. You shall be register to download it for free the workspace location must be the root folder in the git repo then In ProjectExplorer, import an existing project into workspace : MPMD_3dPrinter Rebuild all files in Release Mode and load your image into target memory

There are two relevant #define options for debugging on actual hardware: STM32_USE_BOOTLOADER in configuration_STM.h determines whether the program will be compiled for loading by a bootloader. See bootloader binary for more information. If you are debugging on the actual printer you can comment this line out. STM32_USE_USB_CDC in configuration.h determines whether the program will use the USB CDC Virtual COM Port for communication or USART2 (located on the 5 pin molex connector on the bottom of the board) for communications. I had experimented with using the UART directly earlier on to see if it would be a lower latency connection for interfacing with a raspberry pi, but ended up using the USB interface instead. There may still be some gains to be made, especially on lower-powered raspberry pi zero w boards, but it would take some work and soldering skills to make this work. Currently using the USB is required when the LCD screen is enabled.

How to debug the FW?

Debugging directly on the printer hardware requires access to the 4-pin SWD jumper on the bottom of the board. You will need to solder on some header pins to connect directly. I use an ST-link V2 as my debugger, but any OpenOCD compatible Cortex M-class debugger should work fine.
The MCU on this board has been locked down with the security read-out protection set to level 1, meaning that any attempt to re-flash any memory location or change the security bits results in a full erase of the flash memory. Therefore care should be taken when going down the route of debugging directly on the actual printer. I've included the original bootloader that I was able to extract so that you can restore the stock software without risking bricking your printer. To enable debugging on the board with an ST-link debugger, you will need to start the STM32 ST-LINK utility and change the Read Out Protection level to 0. This will trigger a full erase, but will allow you to debug the firmware directly.

Recent changes

Marlin4MPMD - v1.2.2 7/31/2018

  • Many reliability fixes that should hopefully prevent some of the common issues people were experiencing
    • Automatically re-initialize the SD card in case of ejecting the card unsafely
    • Automatically call M501 on powerup to restore saved settings, this requires the SD card to be present
    • Fixed issues where LCD would be unresponsive until connected by USB
  • M501 no longer triggers the LCD build menu
  • Updated the thermistor table to better match the stock firmware
  • Updated temp sensor measurement for better accuracy and performance
  • Bed switches light red when pressed
  • Added M665 D,E,F individual delta radius adjust
  • Added G29 P0,1,2 settings to enable/disable single point delta-height adjust
    • G29 P0/2 will detect incorrectly configured steps per mm and (hopefully) adjust automatically
  • Calling M421 E will now clear out non-probeable points for you before extrapolating
  • Calling G28 when above the delta clip height (approximately 107mm) will no longer drop to a safe build height to prevent crashing into tall prints that exceed the safe build height
  • Prevent thermal runaway errors when slewing the extruder after pre-heating the bed for 5A power supplies. Bed temperature will still droop significantly, so account for this before starting the print

Marlin4MPMD - v1.2.1 7/11/2018

  • Added fix for the LCD that causes the build menu to pop up appropriately when printing from USB, previously the LCD could time out and cause the print to fail when it issued commands to change movement to relative mode
  • Added fixes to PID tuning to prevent overshoots and fail during autotune
  • Added support M73 command to set the progress bar percent. Use M73 P0 in your start g-code and M73 P100 in your end g-code to ensure that the build menu is called and finished (M109,M190, and M24 also trigger it, but just to be safe). You can also use plugins such as: M73 Progress to sync octoprint progress with your print, or manually insert M73 commands in your g-code. M73 is ignored when printing from SD.

Marlin4MPMD - v1.2.0 7/09/2018

Third release brings things pretty close to parity to the stock firmware changes include:

  • Added MalyanLCD support from xC0000005's port of Marlin 2.0 for use with the Malyan M200. There is a potential to use that effort for a Marlin2.0 port for MPMD, but it will likely require some more effort. All stock GUI functions should be implemented now.
  • Changed the way mesh bed leveling is done. Uses a fixed 7x7 mesh now and is persistent through G28 homing. You can now save/load meshes using the M500/M501 command. You can also set individual points by the M421 command. See above for more details
  • Bugfixes for the SD card
  • Added delta angle trim, use M665 XYZ

Marlin4MPMD - v1.1.0 6/24/2018

Second release to address some of the limitations of the first release. Most notably:

  • Limited current consumption during heating to prevent overdriving the power supply and triggering a reset
  • Immediately on reset, detect a hot extruder and pull away nozzle in case of power supply glitch or outage
  • Added suppport for SD cards!
  • Various reliability fixes and improvments to USB
  • Added support for M500/M501 by saving calibration settings to M_CFG.G on the SD card

Marlin4MPMD - v1.0.0 6/14/2018

This is the first release as a proof of concept that third party software can be ported to this device without altering the mainboard Performance has been comparable to the stock firmware when connected to a PC/Raspberry Pi over USB with significant improvements in the heating control and also in the interface latency.

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