This RepRap firmware is a mashup between <ahref="https://github.com/kliment/Sprinter">Sprinter</a>, <ahref="https://github.com/simen/grbl/tree">grbl</a> and many original parts.
The default baudrate is 250000. This baudrate has less jitter and hence errors than the usual 115200 baud, but is less supported by drivers and host-environments.
Differences and additions to the already good Sprinter firmware:
Also, with just a 20x4 or 16x2 display, useful data is shown.
*SD card folders:*
If you have an SD card reader attached to your controller, also folders work now. Listing the files in pronterface will show "/path/subpath/file.g".
You can write to file in a subfolder by specifying a similar text using small letters in the path.
Also, backup copies of various operating systems are hidden, as well as files not ending with ".g".
*SD card folders:*
If you place a file auto[0-9].g into the root of the sd card, it will be automatically executed if you boot the printer. The same file will be executed by selecting "Autostart" from the menu.
First *0 will be performed, than *1 and so on. That way, you can heat up or even print automatically without user interaction.
*Endstop trigger reporting:*
If an endstop is hit while moving towards the endstop, the location at which the firmware thinks that the endstop was triggered is outputed on the serial port.
This is useful, because the user gets a warning message.
However, also tools like QTMarlin can use this for finding acceptable combinations of velocity+acceleration.
*Coding paradigm:*
Not relevant from a user side, but Marlin was split into thematic junks, and has tried to partially enforced private variables.
This is intended to make it clearer, what interacts which what, and leads to a higher level of modularization.
We think that this is a useful prestep for porting this firmware to e.g. an ARM platform in the future.
A lot of RAM (with enabled LCD ~2200 bytes) was saved by storing char []="some message" in Program memory.
In the serial communication, a #define based level of abstraction was enforced, so that it is clear that
some transfer is information (usually beginning with "echo:"), an error "error:", or just normal protocol,
necessary for backwards compatibility.
*Interrupt based temperature measurements:*
An interrupt is used to manage ADC conversions, and enforce checking for critical temperatures.
This leads to less blocking in the heater management routine.
Non-standard M-Codes, different to an old version of sprinter:
* M202 - Set max acceleration in units/s^2 for travel moves (M202 X1000 Y1000) Unused in Marlin!!
* M203 - Set maximum feedrate that your machine can sustain (M203 X200 Y200 Z300 E10000) in mm/sec
* M204 - Set default acceleration: S normal moves T filament only moves (M204 S3000 T7000) im mm/sec^2 also sets minimum segment time in ms (B20000) to prevent buffer underruns and M20 minimum feedrate
* M206 - set home offsets. This sets the X,Y,Z coordinates of the endstops (and is added to the {X,Y,Z}_HOME_POS configuration options (and is also added to the coordinates, if any, provided to G82, as with earlier firmware)
* M220 - set build speed mulitplying S:factor in percent ; aka "realtime tuneing in the gcode". So you can slow down if you have islands in one height-range, and speed up otherwise.
* M221 - set the extrude multiplying S:factor in percent
* M400 - Finish all buffered moves.
Temperature variables:
* M301 - Set PID parameters P I and D
* M302 - Allow cold extrudes
* M303 - PID relay autotune S<temperature> sets the target temperature. (default target temperature = 150C)
Advance:
* M200 - Set filament diameter for advance
* M205 - advanced settings: minimum travel speed S=while printing T=travel only, B=minimum segment time X= maximum xy jerk, Z=maximum Z jerk
EEPROM:
* M500 - stores paramters in EEPROM. This parameters are stored: axis_steps_per_unit, max_feedrate, max_acceleration ,acceleration,retract_acceleration,
