How To Activate spindle linearization and setting the piecewise ?

[hanifhan]

my RPM doesnt seem accurate when i use an tachometer , so i want to try using spindle linearization , in previous GRBL i can use it with enabling piecewise , but how to activate it in GRBLHal ?

[terjeio]

It is enabled here. Enabling givess access to settings for the values: $66 - $69. These are a bit odd as they each holds a comma separated list of 3 float values:
RPM, RPM_LINE_A. RPM_LINE_B
or a single 0 or a blank line to disable the entry.

I need to revisit this and document the settings...

[hanifhan]

im using stm32f446xx driver ,
but still , i dont know how to fill the piecewise setting in this GRBLHal ,
Thanks in advance for your response

[terjeio]

Fix committed.

but i cant find the $66-$69 setting , where should i fill it ?

In ioSender you can find the settings under the Spindle grouping:

Other senders migth not show these settings, then you have to set the values from the MDI or console. Another fallback will be to connect with a terminal program such as puTTY. The final fallback will be to change the default values in config.h and recompile/reflash.

FYI I have moved the enable setting to config.h.

[hanifhan]

hi thanks its help me a lot
i've try that settings , but i think the computation still have a problem
i get the piecewise by https://github.com/terjeio/grblHAL/blob/master/doc/script/fit_nonlinear_spindle.py
and of course i have change the PWM Point 1 -3 to 30,50, and 70
since the SPINDLE_PWM_MAX_VALUE is 100
but the result is my maximum pwm voltage only 0,9 volt , if i disable the linearisation my maximum pwm voltage normal in 9.9 v

[terjeio]

Use the RPM values. SPINDLE_PWM_MAX_VALUE is a percentage and relates to the max RPM setting ($36).

[hanifhan]

i do my piecewise like i sent the picture below , did i do wrong ?

[hanifhan]

i do my piecewise like that, where did i do wrong ? , because the output PWM only became 0,89 volt if i activate and set the linearization

[hanifhan]

i try using 1K RPM

[terjeio]

Are you compiling locally or are you using the Web Builder?

[hanifhan]

Using replit

[terjeio]

Using replit

I do not know what "replit" is, assuming you are compiling locally then this line should be changed from:

core/spindle_control.c

Line 718 in cad1dc8

pwm_value = floorf(pwm_data->piece[idx].start * rpm - pwm_data->piece[idx].end);

to:
pwm_value = floorf((pwm_data->piece[idx].start * rpm - pwm_data->piece[idx].end) * pwm_data->pwm_gradient);

and $30/$31 set to the actual min/max before collecting the values. $30/$31 should not be changed after collecting as this will change the gradient value. An example that seems to work correctly (with a very much linear profile):

CONFIG:
  N_pieces: 4
  PWM_min: 0.0
  PWM_max: 3000.0
  PWM_point1: 100.0
  PWM_point2: 1400.0
  PWM_point3: 2800.0
  N_data: 21
  PWM_set:  [   0.  150.  300.  450.  600.  750.  900. 1050. 1200. 1350. 1500. 1650.
 1800. 1950. 2100. 2250. 2400. 2550. 2700. 2850. 3000.]
  RPM_measured:  [   0.  147.  297.  447.  597.  747.  897. 1047. 1197. 1347. 1497. 1647.
 1797. 1947. 2097. 2247. 2397. 2547. 2697. 2847. 2997.]

SOLUTION:

[Update these #define values and uncomment]
[ENABLE_PIECEWISE_LINEAR_SPINDLE in config.h.]
#define N_PIECES 4
#define RPM_MAX 2997.0
#define RPM_MIN 0.0
#define RPM_POINT12 97.0
#define RPM_POINT23 1397.0
#define RPM_POINT34 2797.0
#define RPM_LINE_A1 1.030928e+00
#define RPM_LINE_B1 3.566591e-20
#define RPM_LINE_A2 1.000000e+00
#define RPM_LINE_B2 -3.000000e+00
#define RPM_LINE_A3 1.000000e+00
#define RPM_LINE_B3 -3.000000e+00
#define RPM_LINE_A4 1.000000e+00
#define RPM_LINE_B4 -3.000000e+00

[To operate over full model range, manually write these]
['$' settings or alter values in defaults.h. Grbl will]
[operate between min($30,RPM_MAX) and max($31,RPM_MIN)]
$30=2997.0 (rpm max)
$31=0.0 (rpm min)
$66=3.459593e-20,1.030928e+00,3.566591e-20 (piece 1)
$67=9.700000e+01,1.000000e+00,-3.000000e+00 (piece 2)
$68=1.397000e+03,1.000000e+00,3.459593e-20 (piece 3)
$69=2.797000e+03,1.000000e+00,3.459593e-20 (piece 4)

[No cpu_map.h changes required.]

[hanifhan]

wow , i've changed the code as ur command and its work perfectly ,thanks a lot :))