Firmware Capabilities Protocol

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Contents

Idea

While it is nice if a firmware supports some special features, it would be even better if hosts would detect that these are available so they start using them. Especially with the wild growth of firmware forks and versions, no host can know which variant can handle what. So at least for Repetier-Firmware we introduce with version 1.0 a new simple protocol to tell hosts what features are available, so they can activate them.

Protocol definition

To make it easy to detect, a standard M115 report gets now extended by one or more lines, each line telling what capability. These lines have the following format:

Cap:<NameOfCapability>:<0 or 1>

Notice: no spaces allowed, Name is upper case with underline to separate words. Lines MUST start with "Cap:" so it can be parsed very quickly by hosts.

The last value indicates if that capability is supported or not. The simple absence of a message is not enough since it would be possible, that the firmware simply does not report capabilities at all and host has to make assumptions like showing eeprom editor even with the risk that it is not available. Whereas a 0 value shows that a function is known, but the functionality is not implemented/active.

Knowing different developers will add other capabilities is no real problem as long as all names differ, so hosts can distinguish them by name. Hosts not understanding a name simply ignore them.

Currently-defined capabilities

Cap:EEPROM

Defines if firmware is compiled with EEPROM support.

Cap:AUTOREPORT_TEMP

The firmware can automatically report temperatures. This feature must be enabled by M155 S[interval] so older hosts won't get redundant reports from M105 and this feature.

Cap:PROGRESS

The firmware supports the progress protocol:

  • M530 S<printing> L<layer> - Enables explicit printing mode (S1) or disables it (S0). L can set layer count.
  • M531 filename - Set the filename being printed.
  • M532 X<percent> L<curLayer> - Update current print state progress (X=0..100) and layer L.

This allows a host to enable a special information mode on LCD display, so users see progress in percent, model being printed, layer being printed, and total layer count. (Hosts can also use M117 to show time remaining on the LCD status line.)

This feature should only be enabled if a display is available to show it, otherwise the extra commands are useless.

Cap:AUTOLEVEL

The firmware supports auto-leveling with G29.

Cap:Z_PROBE

The firmware supports z probing with G30.

Cap:SOFTWARE_POWER

The firmware supports enabling/disabling power with M80 and M81.

Cap:TOGGLE_LIGHTS

The firmware supports turning the case lights on/off with M355 S1 and M355 S0. (May also support setting case light brightness with S values 2-255.)

Cap:EMERGENCY_PARSER

The firmware supports immediate execution of commands M108, M112, and M410. With this capability M108 can be used to break out of M0/M1, M109, and M190.