M578 Firmware

[Autumn Pitz]

What types of usb sticks are you using? I have found that cheap no-name products are hit and miss. What happens if you plug the stick into the back usb port? You can also update the firmware using the embedded web server.

GCodes are a widely used machine control language. They are human readable and editable. This page describes the RepRapFirmware supported GCodes. RepRapFirmware follows the philosophy of "GCode everywhere", in essence the users or external program's interaction with the firmware should be through GCodes. There are GCodes for all supported control and configuration inputs along with status and debugging information.

RepRapFirmware GCodes were originally based on the information from the RepRap wiki GCode page. There are some GCodes listed on that page that are not implemented in RepRapFirmware. More details can be found on the GCodes not implemented page.

A key difference from other 3d printer firmwares is not employing a separate command set (other than GCodes) to configure the printer. To that end RepRapFirmware has a large collection of configuration GCodes that allow the behaviour of the machine to be controlled. For some examples of when these GCodes are employed have a look at these wiki pages:

The advantage of "GCode everywhere" is the same commands can be send from any of the GCode sources, and originate from the user, a UI, macro or file and it will generate the same response from the firmware. This greatly improves the ease and power of firmware configuration and operation.

A RepRap GCode is a list of fields that are separated by white spaces or line breaks. A field can be interpreted as a command, parameter, or for any other special purpose. It consists of one letter directly followed by a number, or can be only a stand-alone letter (Flag). The letter gives information about the meaning of the field (see the list below in this section). Numbers can be integers (128) or fractional numbers (12.42), depending on context. For example, an X coordinate can take integers (X175) or fractionals (X17.62), but selecting extruder number 2.76 would make no sense. In this description, the numbers in the fields are represented by nnn as a placeholder.

In RepRapFirmware, some parameters can be followed by more than one number, with colon used to separate them. Typically this is used to specify extruder parameters, with one value provided per extruder. If only one value is provided where a value is needed for each extruder, then that value is applied to all extruders.

The original NIST GCode standard requires GCode interpreters to be case-insensitive, except for characters in comments. However, not all 3D printer firmwares conform to this and some recognise uppercase command letters and parameters only.

RepRapFirmware version 1.19 and later is case-insensitive, except for characters within quoted strings. RepRapFirmware version 1.18 and earlier accept only uppercase letters for command and parameter letters.

In RepRapFirmware, quoted strings are permitted anywhere a string parameter is expected. This allows file names, WiFi passwords etc. to contain spaces, semicolons and other characters that would otherwise not be permitted. Double-quote characters are used to delimit the string, and any double-quote character within the string must be repeated.

Unfortunately, many GCode sender programs convert all characters to uppercase and don't provide any means to disable this feature. Therefore, within a quoted-string, the single-quote character is used as a flag to force the following character to lowercase. If you want to include a single quote character in the string, use two single quote characters to represent one single quote character.

You can leave both of these out - RepRapFirmware will still work, but it won't do checking. You have to have both or neither though. If only one appears, it produces an error. See this forum thread for an example of usage, in this case sending GCode to the PanelDue port without disabling checksums.

In RepRapFirmware 3.01 and later, if the line begins with a recognised keyword (optionally preceded by N and a line number, and/or space or tab characters) then that whole line of GCode is interpreted as a meta-command. Recognised keywords are:

A line that does not start with one of these keywords must start with command letter G, M or T or be empty apart from white space and comments. Exception: when in CNC or Laser mode, if a line does not start with a G, M or T command but nevertheless has other fields, and the previous line that included a command was a G0, G1, G2 or G3 command, then the previous command will be repeated with values from the new fields. This is to support GCode generated for CNC machines.

RepRapFirmware allows multiple G- and M-commands to be included in a single line. Each occurrence of G or M on the line that is preceded by a space or tab character and is not inside a quoted string or a meta command starts a new command. In RRF 3.2 and later, the space or tab character is not required.

Important: a command that invokes a macro file (such as G28, G29, G32 and M98) must be the last command in that line of GCode, because any following commands on the same line will not be executed. A T (tool change) command must be on a line by itself.

RepRapFirmware stores regular G0, G1, G2 and G3 movement commands in a 'move queue' internally for execution, equivalent to a look-ahead buffer. These commands are acknowledged when they are placed in the queue. This means that there is no appreciable delay before a command is acknowledged unless the move queue is full, and that sequences of line segments can be plotted without coming to a stop between one and the next.

Some non-movement commands are also queued when executed from a job file or a macro, in a 'deferred command queue'. This operates in parallel to the 'move queue', and together the two queues operate as a single logical queue, and generally can be considered as one queue.

As soon as one of these commands is received it is acknowledged and stored locally in the queue. If the queue is full, then the acknowledgement is delayed until space for storage in the queue is available. PC host programs rely on this for flow control when the controller electronics does not support device level flow control.

As a general rule, any G or M command can be sent at any time. This means all settings can be changed 'on the fly', i.e. while printing. This does not take into account logical considerations, or individual pre-requisites for individual commands. For example, sending new values for M566 'jerk', M201 'acceleration', or M203 'max speed' while printing is a great way to tune these values. However, while it is theoretically possible to change M563 'define a tool' while printing, it's probably not a good idea.

In RepRapFirmware 2.03 and later, you can create custom GCodes, so long as the GCode is not already implemented. If you try to execute a G- or M-command that RRF does not implement, it will execute a system macro of that name if it exists. For example, if you send G40 then it will execute /sys/G40.g if it exists; and if you send M5000 then it will execute /sys/M5000.g if it exists.

1Where a tool has more than one extruder drive then Ennn:nnn:nnn etc is supported to allow for the individual movement of each to be controlled directly. This overrides the extruder mix ratio set with M567

Very important! If you use M452 to put your machine into Laser mode, when upgrading firmware from 2.01 or earlier to 2.02 or later you must replace all S parameters in G0/G1 commands in homing files etc. by H parameters. This is because S is now used to control laser power, for compatibility with programs that generate GCode files for laser cutters.

The meaning of the S parameter has changed over successive versions of RepRapFirmware. It currently sets the laser power when M452 Laser mode is set, but was also used for homing behaviour. See below.

To increase the speed of raster engraving, raster clustering mode has been implemented. A single G1 move is split up into equal portions by multiple values in the S parameter, eg G1 X50 S100:50:25:50:100 would move 50mm and change the laser power every 10mm. This allows more commands to fit in the command buffer, to keep speed up. Laser cutter software such as Lightburn supports raster clustering.

However, in the above example, we set a feedrate of 1500mm/minute on line 1, then do the move described above accelerating to a feedrate of 3000 mm/minute as it does so. The extrusion will accelerate along with the X and Y movement, so everything stays synchronized.

Feedrate is treated as simply another variable (like X, Y, Z, and E) to be linearly interpolated. This gives complete control over the acceleration and deceleration of the printer head in such a way that ensures that everything moves smoothly together, and the right volume of material is extruded at all points. The feedrate specified may not be reached due to a lower feedrate limit being configured, or the move being too short for the axis to accelerate and decelerate in time.

The firmware keeps track of the exact number of microsteps sent to each movement axis using a 32-bit signed integer microstep counter, this limits the maximum absolute move and axis length to (2^31 - 1) microsteps. This does not apply to extruder drives. The firmware multiplies the requested axis position (after adding any offsets) by the steps/mm to get the required microstep position and the microstep counter accumulates across multiple moves, as the axis position increases it increments, as it decreases it decrements. The maximum size of the microstep counter is only an issue for situations where an axis needs to accommodate one or more moves or an overall axis length that would overflow the counter (i.e. an extremely long axis, or an extremely high resolution axis). In typical uses this is not a concern, for example on a standard linear axis using 160 microsteps/mm an axis of over 13km is supported. In cases where the microstep counter is not sufficient (e.g. a very high resolution rotary axis moving for a very long time) G92 can be used to set the origin to a new point on the axis and thus reset the counter.

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