22 lines
2.9 KiB
Plaintext
Executable File
22 lines
2.9 KiB
Plaintext
Executable File
Runtime commands for Grbl
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In normal operation, grbl accepts g-code blocks followed by a carriage return. Each block is then parsed, processed, and placed into a ring buffer with computed acceleration profiles. Grbl will respond with an 'ok' or 'error:XXX' for each block received.
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As of v0.8, grbl features multi-tasking events, which allow for immediate execution of run-time commands regardless of what grbl is doing. With this functionality, direct control of grbl may be possible, such as a controlled decelerating feed hold, resume, and system abort/reset. In addition, this provides the ability to report the real-time status of the CNC machine's current location and feed rates.
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How it works: The run-time commands are defined as special characters, which are picked off the serial read buffer at an interrupt level. The serial interrupt then sets a run-time command system flag for the main program to execute when ready. The main program consists of run-time command check points placed strategically in various points in the program, where grbl maybe idle waiting for room in a buffer or the execution time from the last check point may exceed a fraction of a second.
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How to interface: From a terminal connection, run-time commands may be sent at anytime via keystrokes. When streaming g-code, the user interface should be able to send these special characters independently of the stream. Grbl will not write these run-time command special characters to the buffer, so they may be placed anywhere in the stream at anytime, as long as there is room in the buffer. Also, ensure that the g-code program being streamed to grbl does not contain any of these special characters in the program. These characters may be defined per user requirements in the 'config.h' file.
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Run-time commands:
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- Feed Hold: This initiates an immediate controlled deceleration of the streaming g-code program to a stop. The deceleration, limited by the machine acceleration settings, ensures no steps are lost and positioning is maintained. Grbl may still receive and buffer g-code blocks as the feed hold is being executed. Once the feed hold completes, grbl will replan the buffer and resume upon a 'cycle start' command.
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- Cycle Start: (a.k.a. Resume) For now, cycle start only resumes the g-code program after a feed hold. In later releases, this may also function as a way to initiate the steppers manually when a user would like to fill the planner buffer completely before starting the cycle.
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- Reset: This issues an immediate shutdown of the stepper motors and a system abort. The main program will exit back to the main loop and re-initialize grbl.
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- Status Report: (TODO) In future releases, this will provide real-time positioning, feed rate, and block processed data, as well as other important data to the user. This also may be considered a 'poor-man's' DRO (digital read-out), where grbl thinks it is, rather than a direct and absolute measurement.
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