G-code extensions

TG Motion uses several G-code extensions to simplify G-code programming.

Parametric programming

There are 100 parameters (P00 - P99) which can be used instead of fixed numerical values in any G-code address. All the values are expressed as floating point values with precision of 15-17 digits (float64_t precision).
During G-code execution system uses the value stored in the parameter. Before use, the value should be defined in an assignment.

P37 = 10 + 25 * SIN(45)
G0  X 10  Z P37

Note

Because the parameters are marked as Pxx, the address P is reserved and can be used ONLY for parameters.

Mathematic expressions

Mathematic expression can contain:

• numbers and/or parameters (P00 - P99)
• mathematic operations
  • addition +
  • subtraction -
  • multiplication *
  • division /
  • modulo %
  • power of ^
• mathematic functions (names are case insensitive)
  • SIN(angle) - sinus, angle is in degrees
  • COS(angle) - cosines, angle is in degrees
  • TAN(angle) - tangens, angle is in degrees
  • ASIN(val) - arcus sinus
  • ACOS(val) - arcus cosines
  • ATAN(val) - arcus tangens
  • ATAN2(y, x) - arcus tangens of opposite leg to adjacent leg of a triangle
  • ABS(val) - absolute value
  • FABS(val) - absolute value
  • SQRT(val) - square root
  • LOG10(val) - logarithm of base 10
  • LOG(val) - natural logarithm
  • HYPOT(a, b) - SQRT(a*a + b*b)
  • PI() - pi number 3.1415926....
  • FLOOR(val) - nearest lower integer value of val
  • CEIL(val) - nearest higher integer value of val
  • ReadPLCLong(address) - read integer value from PLC memory at address (note address must be > 0)
  • ReadPLCDouble(address) - read float64_t floating point value from PLC memory at address (note address must be > 0)
  • WritePLCLong(address, arg) - write arg as integer value to PLC memory at address (note address must be > 0). Note that WritePLCLong must be on the right side of an assignment. It returns the previous value in the PLC memory.

    P1 = WritePLCLong(1024, P2)

  • WritePLCDouble(address, arg) - write arg as float64_t floating point value to PLC memory at address (note address must be > 0). Must be on the right side of an assignment.
• brackets () which can modify/clarify the priority of mathematical operations

Expressions can be entered directly after the address letter:

G0  X P21+P22  Z P23

Or as an assignment to a parameter:

P1 = ReadPLCDouble(1024) + SIN(ABS(ReadPLCLong(2048)))
G1 X P1

Priority of operations

1. brackets
2. mathematic functions
3. power of ^
4. multiplication and division * /
5. addition and subtraction + -

Subroutines and labels

Any block of G-code text can act as a subroutine. Subroutine starts with a label or line number and ends with M17 or RETURN. The label is text in the begin of G29 comment function or can be declared independently on a separate line, then it must end with colon :
Functions G25, G26 or keyword CALL can be used to call the subroutine. Subroutines must be in the same G-code file as their call(s).

G1 X... Y...
CALL Subroutine1
...
M2
 
 
G29 Subroutine1
G2 X... Y... I... J...
...
RETURN

The same meaning with independent label:

G1 X... Y...
CALL Subroutine1
...
M2
 
Subroutine1:
G2 X... Y... I... J...
...
RETURN

Using line number N:

G1 X... Y...
G25 L 1000
...
M2
 
N 1000 G2 X... Y... I... J...
...
RETURN

Loops

There are two loop program constructs available: FOR loop and WHILE loop.
FOR loop syntax is:
FOR initial_value TO end_value [STEP step_value]
  ... loop body
END

Example:

P2 = -10 // end Z coord
P3 = 2   // safe Z coord
FOR P1 = 0 TO P2 STEP -1
  G1  Z P1
  G0  Z P3
END

Every FOR loop must end with keyword END.

WHILE loop syntax is:
WHILE condition
  .. loop body
END

Example:

P1 = 0   // actual Z coord
P2 = -10 // end Z coord
P3 = 2   // safe Z coord
WHILE P1 > P2
  G1  Z P1
  G0  Z P3
  P1 = P1-1
END
G1  Z P2
G0  Z P3
END

The condition could be:

Symbol	Description
>	Greater than
<	Less than
==	Equal to
!=	Not equal to
<>	Not equal to
<=	Less or equal to
>=	Greater or equal to

Conditional jumps

Sometimes it is useful to skip some block of G-code parts depending on some condition. Conditional jumps are used for this situation.
Syntax is:
IF condition THEN
  ...
ELSE
  ...
END

If the condition after the IF keyword is met, the code till ELSE is executed, otherwise the code between ELSE and END is executed.
Example:

FOR P21 = 60 TO 45-P22 STEP P22
  IF P24 == 0 THEN
    CALL Cone
  ELSE
    CALL Remove
    P23 = P23 + P24
  END
  P25 = P25 + P26
END

Conditional jumps can be used to exit from loop, exit from subroutine or continue loop on a next iteration:

• IF condition BREAK - if the condition is valid, exit from the loop and continues program execution after the END keyword of the loop.
  
• IF condition RETURN - if the condition is valid, exit from subroutine
• IF condition CONTINUE - if the condition is valid, slip the rest of loop body and goes to the next loop iteration