tutorial.lyx

CNC 的开放码,EMC2 V2.2.8版

 We can call them anything we want, for this example they will be 
\family typewriter 
X_vel
\family default 
 and 
\family typewriter 
Y_vel
\family default 
.
 The signal 
\family typewriter 
X_vel
\family default 
 is intended to run from the cosine output of the signal generator to the
 velocity input of the first step pulse generator.
 The first step is to connect the signal to the signal generator output.
 To connect a signal to a pin we use the net command.
\layout LyX-Code

halcmd:
\series bold 
 net X_vel <= siggen.0.cosine
\layout Standard

To see the effect of the 
\family typewriter 
net
\family default 
 command, we show the signals again:
\layout LyX-Code

halcmd:
\series bold 
 show sig
\series default 

\newline 
ignals:
\newline 
Type      Value      Name
\newline 
float   0.00000e+00  X_vel
\newline 
                         <== siggen.0.cosine
\layout Standard

When a signal is connected to one or more pins, the show command lists the
 pins immediately following the signal name.
 The 
\begin_inset Quotes eld
\end_inset 

arrow
\begin_inset Quotes erd
\end_inset 

 shows the direction of data flow - in this case, data flows from pin 
\family typewriter 
siggen.0.cosine
\family default 
 to signal 
\family typewriter 
X_vel
\family default 
.
 Now let's connect the 
\family typewriter 
X_vel
\family default 
 to the velocity input of a step pulse generator:
\layout LyX-Code

halcmd:
\series bold 
 net X_vel => freqgen.0.velocity
\layout Standard

We can also connect up the Y axis signal 
\family typewriter 
Y_vel
\family default 
.
 It is intended to run from the sine output of the signal generator to the
 input of the second step pulse generator.
 The following command accomplishes in one line what two 
\family typewriter 
net
\series bold 
 
\family default 
\series default 
commands accomplished for 
\family typewriter 
X_vel
\family default 
:
\layout LyX-Code

halcmd:
\series bold 
 net Y_vel siggen.0.sine => freqgen.1.velocity
\layout Standard

Now let's take a final look at the signals and the pins connected to them:
\layout LyX-Code

halcmd:
\series bold 
 show sig
\series default 

\newline 
Signals:
\newline 
Type      Value      Name
\newline 
float   0.00000e+00  X_vel
\newline 
                         <== siggen.0.cosine
\newline 
                         ==> freqgen.0.velocity
\newline 
float   0.00000e+00  Y_vel
\newline 
                         <== siggen.0.sine
\newline 
                         ==> freqgen.1.velocity
\layout Standard

The 
\family typewriter 
show sig
\family default 
 command makes it clear exactly how data flows through the HAL.
 For example, the
\family typewriter 
 X_vel
\family default 
 signal comes from pin 
\family typewriter 
siggen.0.cosine
\family default 
, and goes to pin 
\family typewriter 
freqgen.0.velocity
\family default 
.
\layout Subsection

Setting up realtime execution - threads and functions
\layout Standard

Thinking about data flowing through 
\begin_inset Quotes eld
\end_inset 

wires
\begin_inset Quotes erd
\end_inset 

 makes pins and signals fairly easy to understand.
 Threads and functions are a little more difficult.
 Functions contain the computer instructions that actually get things done.
 Thread are the method used to make those instructions run when they are
 needed.
 First let's look at the functions available to us:
\layout LyX-Code

halcmd:
\series bold 
 show funct
\newline 

\series default 
Exported Functions:
\newline 
Owner CodeAddr   Arg    FP  Users  Name
\newline 
 03   D89051C4 D88F10FC YES    0   siggen.0.update
\newline 
 02   D8902868 D88F1054 YES    0   freqgen.capture_position
\newline 
 02   D8902498 D88F1054 NO     0   freqgen.make_pulses
\newline 
 02   D89026F0 D88F1054 YES    0   freqgen.update_freq
\layout Standard

In general, you will have to refer to the documentation for each component
 to see what its functions do.
 In this case, the function 
\family typewriter 
siggen.0.update
\family default 
 is used to update the outputs of the signal generator.
 Every time it is executed, it calculates the values of the sine, cosine,
 triangle, and square outputs.
 To make smooth signals, it needs to run at specific intervals.
 
\layout Standard

The other three functions are related to the step pulse generators:
\layout Standard

The first one, 
\family typewriter 
freqgen.capture_position
\family default 
, is used for position feedback.
 It captures the value of an internal counter that counts the step pulses
 as they are generated.
 Assuming no missed steps, this counter indicates the position of the motor.
\layout Standard

The main function for the step pulse generator is 
\family typewriter 
freqgen.make_pulses
\family default 
.
 Every time 
\family typewriter 
make_pulses
\family default 
 runs it decides if it is time to take a step, and if so sets the outputs
 accordingly.
 For smooth step pulses, it should run as frequently as possible.
 Because it needs to run so fast, 
\family typewriter 
make_pulses
\family default 
 is highly optimized and performs only a few calculations.
 Unlike the others, it does not need floating point math.
 
\layout Standard

The last function, 
\family typewriter 
freqgen.update_freq
\family default 
, is responsible for doing scaling and some other calculations that need
 to be performed only when the frequency command changes.
\layout Standard

What this means for our example is that we want to run 
\family typewriter 
siggen.0.update
\family default 
 at a moderate rate to calculate the sine and cosine values.
 Immediately after we run 
\family typewriter 
siggen.0.update
\family default 
, we want to run 
\family typewriter 
freqgen.update_freq
\family default 
 to load the new values into the step pulse generator.
 Finally we need to run 
\family typewriter 
freqgen.make_pulses
\family default 
 as fast as possible for smooth pulses.
 Because we don't use position feedback, we don't need to run 
\family typewriter 
freqgen.capture_position
\family default 
 at all.
\layout Standard

We run functions by adding them to threads.
 Each thread runs at a specific rate.
 Let's see what threads we have available:
\layout LyX-Code

halcmd:
\series bold 
 show thread
\series default 

\newline 
Realtime Threads:
\newline 
   Period   FP   Name
\newline 
    1005720 YES  slow    ( 0, 0 )
\newline 
      50286 NO   fast    ( 0, 0 )
\layout Standard

The two threads were created when we loaded 
\family typewriter 
threads
\family default 
.
 The first one, 
\family typewriter 
slow
\family default 
, runs every millisecond, and is capable of running floating point functions.
 We will use it for s
\family typewriter 
iggen.0.update
\family default 
 and 
\family typewriter 
freqgen.update_freq
\family default 
.
 The second thread is 
\family typewriter 
fast
\family default 
, which runs every 50 microseconds, and does not support floating point.
 We will use it for 
\family typewriter 
freqgen.make_pulses
\family default 
.
 To connect the functions to the proper thread, we use the 
\family typewriter 
addf
\family default 
 command.
 We specify the function first, followed by the thread:
\layout LyX-Code

halcmd:
\series bold 
 addf siggen.0.update slow
\series default 

\newline 
halcmd:
\series bold 
 addf freqgen.update_freq slow
\series default 

\newline 
halcmd:
\series bold 
 addf freqgen.make_pulses fast
\layout Standard

After we give these commands, we can run the 
\family typewriter 
show thread
\family default 
 command again to see what happened:
\layout LyX-Code

halcmd:
\series bold 
 show thread
\newline 

\series default 
Realtime Threads:
\newline 
   Period   FP   Name    (Time, Max-Time)
\newline 
    1005720 YES  slow    ( 0, 0 )
\newline 
                  1 siggen.0.update
\newline 
                  2 freqgen.update-freq
\newline 
      50286 NO   fast    ( 0, 0 )
\newline 
                  1 freqgen.make-pulses
\layout Standard

Now each thread is followed by the names of the functions, in the order
 in which the functions will run.
\layout Subsection

Setting parameters
\layout Standard

We are almost ready to start our HAL system.
 However we still need to adjust a few parameters.
 By default, the siggen component generates signals that swing from +1 to
 -1.
 For our example that is fine, we want the table speed to vary from +1 to
 -1 inches per second.
 However the scaling of the step pulse generator isn't quite right.
 By default, it generates an output frequency of 1 step per second with
 an input of 1.000.
 It is unlikely that one step per second will give us one inch per second
 of table movement.
 Let's assume instead that we have a 5 turn per inch leadscrew, connected
 to a 200 step per rev stepper with 10x microstepping.
 So it takes 2000 steps for one revolution of the screw, and 5 revolutions
 to travel one inch.
 that means the overall scaling is 10000 steps per inch.
 We need to multiply the velocity input to the step pulse generator by 10000
 to get the proper output.
 That is exactly what the parameter 
\family typewriter 
freqgen.n.velocity-scale
\family default 
 is for.
 In this case, both the X and Y axis have the same scaling, so we set the
 scaling parameters for both to 10000:
\layout LyX-Code

halcmd:
\series bold 
 setp freqgen.0.velocity-scale 10000
\newline 

\series default 
halcmd:
\series bold 
 setp freqgen.1.velocity-scale 10000
\layout Standard

This velocity scaling means that when the pin 
\family typewriter 
freqgen.0.velocity
\family default 
 is 1.000, the step generator will generate 10000 pulses per second (10KHz).
 With the motor and leadscrew described above, that will result in the axis
 moving at exactly 1.000 inches per second.
 This illustrates a key HAL concept - things like scaling are done at the
 lowest possible level, in this case in the step pulse generator.
 The internal signal 
\family typewriter 
X_vel
\family default 
 is the velocity of the table in inches per second, and other components
 such as 
\family typewriter 
siggen
\family default 
 don't know (or care) about the scaling at all.
 If we changed the leadscrew, or motor, we would change only the scaling
 parameter of the step pulse generator.
\layout Subsection

Run it!
\layout Standard

We now have everything configured and are ready to start it up.
 Just like in the first example, we use the 
\family typewriter 
start
\family default 
 command:
\layout LyX-Code

halcmd:
\series bold 
 start
\layout Standard

Although nothing appears to happen, inside the computer the step pulse generator
 is cranking out step pulses, varying from 10KHz forward to 10KHz reverse
 and back again every second.
 Later in this tutorial we'll see how to bring those internal signals out
 to run motors in the real world, but first we want to look at them and
 see what is happening.
\layout Section


\begin_inset LatexCommand \label{sec:Tutorial - Halscope}

\end_inset 

Taking a closer look with halscope.
\layout Standard

The previous example generates some very interesting signals.
 But much of what happens is far too fast to see with halmeter.
 To take a closer look at what is going on inside the HAL, we want an oscillosco
pe.
 Fortunately HAL has one, called halscope.
\layout Subsection

Starting Halscope
\layout Standard

Halscope has two parts - a realtime part that is loaded as a kernel module,
 and a user part that supplies the GUI and display.
 However, you don't need to worry about this, because the userspace portion
 will automatically request that the realtime part be loaded.
\layout LyX-Code

halcmd:
\series bold 
 loadusr halscope
\layout Standard

The scope GUI window will open, immediately followed by a 
\begin_inset Quotes eld
\end_inset 

Realtime function not linked
\begin_inset Quotes erd
\end_inset 

 dialog that looks like figure 
\begin_inset LatexCommand \ref{fig:Halscope-demo-1}

\end_inset 


\begin_inset Foot
collapsed true

\layout Standard

Several of these screen captures refer to threads named 
\begin_inset Quotes eld
\end_inset 

siggen.thread
\begin_inset Quotes erd
\end_inset 

 and 
\begin_inset Quotes eld
\end_inset 

stepgen.thread
\begin_inset Quotes erd
\end_inset 

 instead of 
\begin_inset Quotes eld
\end_inset 

slow
\begin_inset Quotes erd
\end_inset 

 and 
\begin_inset Quotes eld
\end_inset 

fast
\begin_inset Quotes erd
\end_inset 

.
 When the screenshots were captured, the 
\begin_inset Quotes eld
\end_inset 

threads
\begin_inset Quotes erd
\end_inset 

 component didn't exist, and a different method was used to create threads,
 giving them different names.
 Also, the screenshots show pins, etc, as 
\begin_inset Quotes eld
\end_inset 

stepgen.xxx
\begin_inset Quotes erd
\end_inset 

 rather than 
\begin_inset Quotes eld
\end_inset 

freqgen.xxx
\begin_inset Quotes erd
\end_inset 

.
 The original name of the freqgen module was stepgen, and I haven't gotten
 around to re-doing all the screen shots since it was renamed.
 The name 
\begin_inset Quotes eld
\end_inset 

stepgen
\begin_inset Quotes erd
\end_inset 

 now refers to a different step pulse generator, one that accepts position
 instead of velocity commands.
 Both are described in detail later in this document.
\end_inset 

.
\layout Standard


\begin_inset Float figure
wide false
collapsed false

\layout Standard
\align center 

\begin_inset Graphics
	filename halscope-demo-1.png

\end_inset 


\layout Caption


\begin_inset LatexCommand \label{fig:Halscope-demo-1}

\end_inset 


\begin_inset Quotes eld
\end_inset 

Realtime function not linked
\begin_inset Quotes erd
\end_inset 

 dialog
\end_inset 


\layout Standard

This dialog is where you set the sampling rate for the oscilloscope.
 For now we want to sample once per millisecond, so click on the 1.03mS thread
 
\begin_inset Quotes eld
\end_inset 

slow
\begin_inset Quotes erd
\end_inset 

 (formerly 
\begin_inset Quotes eld
\end_inset 

siggen.thread
\begin_inset Quotes erd
\end_inset 

, see footnote), and leave the multiplier at 1.
 We will also leave the record length at 4047 samples, so that we can use
 up to four channels at one time.
 When you select a thread and then click 
\begin_inset Quotes eld
\end_inset 

OK
\begin_inset Quotes erd
\end_inset 

, the dialog disappears, and the scope window looks something like figure
 
\begin_inset LatexCommand \ref{fig:Halscope-demo-2}

\end_inset 

.
\layout Standard


\begin_inset Float figure
wide false
collapsed false

\layout Standard
\align center 

\begin_inset Graphics
	filename halscope-demo-2.png

\end_inset 


\layout Caption


\begin_inset LatexCommand \label{fig:Halscope-demo-2}

\end_inset 

Initial scope window
\end_inset 


\layout Standard


\begin_inset ERT
status Collapsed

\layout Standard

\backslash 
clearpage
\end_inset 


\layout Subsection

Hooking up the 
\begin_inset Quotes eld