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Expressions and flow control
grblHAL supports parameters, expressions and flow control, LinuxCNC style (with some limitations), if enabled in the config file or in builds made with the Web Builder when RS274 NGC expression support is enabled in the Advanced features tab.
Flow control is limited if streaming G-code from a sender, full support is only available in macros stored on a SD card or in the littlefs filing system.
Follow or comment in this discussion if you want to know more.
To aid debugging a special comment has been made available, output is controlled by setting $534 - set to 1 to enable 0 to disable (default). Numbered and named parameters referenced will be substituted in the generated output, an example:
(debug, metric mode: #<_metric>, coord system: #5220)
outputs
[MSG:metric mode on: 1.000000, coord system: 1.000000]
when metric mode (G21) is on and the current coordinate system is G54.
All predefined parameters defined in NIST RS274NGC version 3 (ref section 3.2.1) are implemented.
Most additional predefined parameters defined by LinuxCNC (ref section 5.2.3.1) are implemented.
| Word | Variable | Word | Variable | Word | Variable |
|---|---|---|---|---|---|
| A | #1 | I | #4 | T | #20 |
| B | #2 | J | #5 | U | #21 |
| C | #3 | K | #6 | V | #22 |
| D | #7 | M | #13 | W | #23 |
| E | #8 | Q | #17 | X | #24 |
| F | #9 | R | #18 | Y | #25 |
| H | #11 | S | #19 | Z | #26 |
Syntax: G65 P<id> (A- B- C- ...)
NOTES: Nesting macro calls is currently not allowed. Axis words ABC and UVW are only available if the corresponding axes are enabled.
| Parameters | Usage | Persistent |
|---|---|---|
| 31 - 5000 | User defined parameters, defaults to 0. | No |
| 5061 - 5069 | Coordinates of a G38 probe result (X, Y, Z, ...) . | No |
| 5070 | G38.3 and G38.5 probe result: 1 if successful, 0 if not. | No |
| 5161 - 5169 | G28 coordinates (X, Y, Z, ...). | Yes |
| 5181 - 5189 | G30 coordinates (X, Y, Z, ...). | Yes |
| 5210 | 1 if G92 offset active, 0 if not. | Depends on $384 setting |
| 5211 - 5219 | G92 offset (X, Y, Z, ...). | Depends on $384 setting |
| 5220 | Coordinate system number for G54 - G59.3, 1 - 9. | Yes |
| 5221 - 5229 | Coordinate system 1, for G54 (X, Y, Z, ...). | Yes |
| 5241 - 5249 | Coordinate system 2, for G55 (X, Y, Z, ...). | Yes |
| 5261 - 5269 | Coordinate system 3, for G56 (X, Y, Z, ...). | Yes |
| 5281 - 5289 | Coordinate system 4, for G57 (X, Y, Z, ...). | Yes |
| 5301 - 5319 | Coordinate system 5, for G58 (X, Y, Z, ...). | Yes |
| 5321 - 5329 | Coordinate system 6, for G59 (X, Y, Z, ...). | Yes |
| 5341 - 5349 | Coordinate system 7, for G59.1 (X, Y, Z, ...). | Yes |
| 5361 - 5369 | Coordinate system 8, for G59.2 (X, Y, Z, ...). | Yes |
| 5381 - 5389 | Coordinate system 9, for G59.3 (X, Y, Z, ...). | Yes |
| 5399 | Result from last M66, wait for input. -1 if timed out. | No |
| 5420 - 5427 | Current position including all offsets (X, Y, Z, ...). | No |
| Name | Usage | Comment |
|---|---|---|
| _vmajor | Major grblHAL version number, currently 1.1. | |
| _vminor | Minor grblHAL version number, currently 0. | |
| _line | Current G Code line number. | |
| _motion_mode | Current motion mode. | See 1 below. |
| _plane | Current plane: 170 - G17, 180 - G18, 190 - G19. | |
| _ccomp | Active cutter compensation: 400 - G40. | |
| _metric | 1 if G21 is active, 0 if not. | |
| _imperial | 1 if G20 is active, 0 if not. | |
| _absolute | 1 if G90 is active, 0 if not. | |
| _incremental | 1 if G91 is active, 0 if not. | |
| _inverse_time | 1 if G93 is active, 0 if not. | |
| _units_per_minute | 1 if G94 is active, 0 if not. | |
| _units_per_rev | 1 if G95 is active, 0 if not. | |
| _coord_system | Current coordinate system: 540 - G54, 550 - G55, ... | |
| _tool_offset | 1 if G43 is active, 0 if not. | |
| _retract_r_plane | 1 if G98 is active, 0 if not. | |
| _retract_old_z | 1 if G99 is active, 0 if not. | |
| _spindle_rpm_mode | 1 if G97 is active, 0 if not. | |
| _spindle_css_mode | 1 if G96 is active, 0 if not. | |
| _ijk_absolute_mode | 1 if G90.1 is active, 0 if not. | |
| _lathe_diameter_mode | 1 if G8 is active, 0 if not. | |
| _lathe_radius_mode | 1 if G7 is active, 0 if not. | |
| _spindle_on | 1 if spindle is running (M3 or M4), 0 if not. | |
| _spindle_cw | 1 if spindle is running clockwise (M3), 0 if not. | |
| _mist | 1 if M7 is active, 0 if not. | |
| _flood | 1 if M8 is active, 0 if not. | |
| _speed_override | 1 if M48 or M50P1 is active, 0 if not. | |
| _feed_override | 1 if M48 or M50p2 is active, 0 if not. | |
| _adaptive_feed | Always 0. | |
| _feed_hold | 1 if M53.1 is active, 0 if not. | |
| _feed | Current value of F. | Not the actual feed rate. |
| _rpm | Current value of S. | Not the actual RPM. |
| _x | Current X coordinate including all offsets. | Same as #5420. |
| _y | Current Y coordinate including all offsets. | Same as #5421. |
| _z | Current Z coordinate including all offsets. | Same as #5422. |
| _a | Current A coordinate including all offsets. | Same as #5423. |
| _b | Current B coordinate including all offsets. | Same as #5424. |
| _c | Current C coordinate including all offsets. | Same as #5425. |
| _u | Current U coordinate including all offsets. | Same as #5426. |
| _v | Current U coordinate including all offsets. | Same as #5427. |
| _w | Current W coordinate including all offsets. | Same as #5428. |
| _current_tool | Number of the tool in the spindle. | Same as #5400. |
| _current_pocket | Always 0. | |
| _selected_tool | Current value of T. | Default -1. |
| _selected_pocket | Always -1. | |
| _value | Return value from the last G65 macro call. | Set to 0 on entry. |
| _value_returned | 1 if last G65 macro call returned a value, 0 if not. | |
| _call_level | N/A |
1 Motion modes:
| Mode | Value |
|---|---|
| G1 | 10 |
| G2 | 20 |
| G3 | 30 |
| G33 | 330 |
| G38.2 | 382 |
| G38.3 | 383 |
| G38.4 | 384 |
| G38.5 | 384 |
| G5 | 50 |
| G5.1 | 51 |
| G73 | 730 |
| G75 | 760 |
| G80 | 800 |
| G81 | 810 |
| G82 | 820 |
| G83 | 830 |
| G85 | 850 |
| G89 | 890 |
| Operators | Precedence |
|---|---|
| ** | Highest |
| *, / and MOD | |
| + and - | |
| EQ, NE, GT, GE, LT and LE | |
| AND, OR and XOR | Lowest |
| Name | Result |
|---|---|
| ABS[arg] | Absolute value |
| ACOS[arg] | Inverse cosine |
| ASIN[arg] | Inverse sine |
| ATAN[arg][arg] | Four quadrant inverse tangent |
| COS[arg] | Cosine |
| EXISTS[arg] | Named parameter exists |
| EXP[arg] | e raised to the given power |
| FIX[arg] | Round down to integer |
| FUP[arg] | Round up to integer |
| LN[arg] | Base-e logarithm |
| ROUND[arg] | Round to nearest integer |
| SIN[arg] | Sine |
| SQRT[arg] | Square root |
| TAN[arg] | Tanget |
| Statement | File macro | Streamed G-Code | Comment |
|---|---|---|---|
| if <expr> | yes | yes | |
| elseif <expr> | yes | yes | |
| else | yes | yes | |
| endif | yes | yes | |
| do | yes | yes | |
| continue | yes | no | |
| break | yes | no | |
| while <expr> | yes | no | |
| endwhile | yes | no | |
| repeat <expr> | yes | no | |
| return [<expr>] | yes | no | |
| alarm <expr> | yes | no | <expr> must evaluate to a valid alarm code2 |
| error <expr> | yes | no | <expr> must evaluate to a valid error code2 |
2 grblHAL specific extension.
2023-06-02