estimate velocity encoder

Hi at all.
I have an encoder capture card and I transfer the counts to a linuxcnc pin. Also knowing the resolution of the encoder as imp/rev , how can I, with a hal component, obtain the rpm speed and the position?

THanks
 

If your encoder hardware does not provide a velocity estimate, you can use
the ddt component on the encoder position (assuming you have a floating
point position) to get a crude velocity estimate.
(Its likely you will need to filter this velocity to get usable numbers at low speeds)

HI PCW.
Thanks for help.
I have test is, ddt.0.out not is rmp/60 , it with about 10 rpm , have value 1000 about.
But ddt component not accept input resolution encoder for estimate the value .

How can have the same out value the hm2.x.encoder.velocity ?

we have only 2 value:
1-encoder resolution 4096imp/rev
2-count in float

If the encoder hardware only provides an integer count you may have to
write an encoder component to convert that integer count to a position number

You can partially do this by stringing together existing LinuxCNC realtime components
(first convert to floating point with conv_s32_float and then use the scale component
for scaling to position)

HI PCW.

My problem not is pin position , but pin velocity.
The hardware write in pin float the increment the count , in positive or negative , depende sense encoder rotation.

The question is, how can estimate a velocity ?
WE have only count increment pin and know the encoder resolution .

So if you have a floating point position
you can run it through the scale and ddt components
to get a velocity estimate.

HI PCW.
The ddt.0.out pin , non are rpm , because if turn encoder about 10 rev/min have big value in output about 1000 or 2000.

That's what the scale component is for...

Normally if you want RPM, say for a spindle "position" is scaled in turns.
(spindles are scaled for 1.0 per turn)