:lang: en
:toc:

[[cha:realtime-components]]
= HAL Component Descriptions

[[sec:stepgen]]
== Stepgen(((stepgen)))

This component provides software based generation of step pulses in
response to position or velocity commands. In position mode, it has a
built in pre-tuned position loop, so PID tuning is not required. In
velocity mode, it drives a motor at the commanded speed, while obeying
velocity and acceleration limits. It is a realtime component only, and
depending on CPU speed, etc, is capable of maximum step rates of 10 kHz
to perhaps 50 kHz. The step pulse generator block diagram shows three block
diagrams, each is a single step pulse generator. The first diagram is for
step type '0', (step and direction). The second is for step type '1'
(up/down, or pseudo-PWM), and the third is for step types 2 through 14
(various stepping patterns). The first two diagrams show position mode
control, and the third one shows velocity mode. Control mode and step type
are set independently, and any combination can be selected.

[[fig:stepgen-block-diagram]]
.Step Pulse Generator Block Diagram position mode(((Stepgen Block Diagram)))
image::images/stepgen-block-diag.png[align="center"]

.Loading `stepgen` component
----
halcmd: loadrt stepgen step_type=<type-array> [ctrl_type=<ctrl_array>]
----

<type-array>:: is a series of comma separated decimal integers. Each
  number causes a single step pulse generator to be loaded, the value of the number
  determines the stepping type.
<ctrl_array>:: is a comma separated
  series of 'p' or 'v' characters, to specify position or velocity mode.
ctrl_type:: is optional, if omitted, all of the step generators
  will be position mode.

For example:

----
halcmd: loadrt stepgen step_type=0,0,2 ctrl_type=p,p,v
----

Will install three step generators. The first two use step type '0'
(step and direction) and run in position mode. The last one uses step
type '2' (quadrature) and runs in velocity mode. The default value for
'<config-array>' is '0,0,0' which will install three type '0'
(step/dir) generators. The maximum
number of step generators is 8 (as defined by MAX_CHAN in stepgen.c).
Each generator is independent, but all are updated by the same
function(s) at the same time. In the following descriptions, '<chan>'
is the number of a specific generator. The first generator is number 0.

.Unloading `stepgen` component
----
halcmd: unloadrt stepgen
----

[[sub:stepgen-pins]]
=== Pins(((HAL stepgen pins)))

On the step type and control type selected.

* '(float) stepgen._<chan>_.position-cmd' - Desired motor position, in
  position units (position mode only).
* '(float) stepgen._<chan>_.velocity-cmd' - Desired motor velocity, in
  position units per second (velocity mode only).
* '(s32) stepgen._<chan>_.counts' - Feedback position in counts,
  updated by 'capture_position()'.
* '(float) stepgen._<chan>_.position-fb' - Feedback position in
  position units, updated by 'capture_position()'.
* '(bit) stepgen._<chan>_.enable' - Enables output steps - when false,
  no steps are generated.
* '(bit) stepgen._<chan>_.step' - Step pulse output (step type 0 only).
* '(bit) stepgen._<chan>_.dir' - Direction output (step type 0 only).
* '(bit) stepgen._<chan>_.up' - UP pseudo-PWM output (step type 1 only).
* '(bit) stepgen._<chan>_.down' - DOWN pseudo-PWM output (step type 1 only).
* '(bit) stepgen._<chan>_.phase-A' - Phase A output (step types 2-14 only).
* '(bit) stepgen._<chan>_.phase-B' - Phase B output (step types 2-14 only).
* '(bit) stepgen._<chan>_.phase-C' - Phase C output (step types 3-14 only).
* '(bit) stepgen._<chan>_.phase-D' - Phase D output (step types 5-14 only).
* '(bit) stepgen._<chan>_.phase-E' - Phase E output (step types 11-14 only).

[[sec:stepgen-parameters]]
=== Parameters(((HAL stepgen parameters)))

* '(float) stepgen.<chan>.position-scale' - Steps per position unit.
  This parameter is used for both output and feedback.
* '(float) stepgen.<chan>.maxvel' - Maximum velocity, in position
  units per second. If 0.0, has no effect.
* '(float) stepgen.<chan>.maxaccel' - Maximum accel/decel rate, in
  positions units per second squared.
  If 0.0, has no effect.
* '(float) stepgen.<chan>.frequency' - The current step rate, in
  steps per second.
* '(float) stepgen.<chan>.steplen' - Length of a step pulse (step
  type 0 and 1) or minimum time in a
  given state (step types 2-14), in nano-seconds.
* '(float) stepgen.<chan>.stepspace' - Minimum spacing between two
  step pulses (step types 0 and 1 only), in nano-seconds. Set to 0 to
  enable the stepgen 'doublefreq' function. To use 'doublefreq' the
  <<sub:parport-functions,parport reset function>> must be enabled.
* '(float) stepgen.<chan>.dirsetup' - Minimum time from a direction
  change to the beginning of the next
  step pulse (step type 0 only), in nanoseconds.
* '(float) stepgen.<chan>.dirhold' - Minimum time from the end of a
  step pulse to a direction change
  (step type 0 only), in nanoseconds.
* '(float) stepgen.<chan>.dirdelay' - Minimum time any step to a step
  in the opposite direction (step
  types 1-14 only), in nano-seconds.
* '(s32) stepgen.<chan>.rawcounts' - The raw feedback count, updated
  by 'make_pulses()'.

In position mode, the values of maxvel and maxaccel are used by the
internal position loop to avoid generating step pulse trains that the
motor cannot follow. When set to values that are appropriate for the
motor, even a large instantaneous change in commanded position will
result in a smooth trapezoidal move to the new location. The algorithm
works by measuring both position error and velocity error, and
calculating an acceleration that attempts to reduce both to zero at the
same time. For more details, including the contents of the 'control
equation' box, consult the code.

In velocity mode, maxvel is a simple limit that is applied to the
commanded velocity, and maxaccel is used to ramp the actual frequency
if the commanded velocity changes abruptly. As in position mode, proper
values for these parameters ensure that the motor can follow the
generated pulse train.

[[sub:stepgen-step-types]]
=== Step Types(((HAL stepgen Step Types)))

Step generator supports 15 different _step sequences_:

.Step Type 0

Step type 0 is the standard step and direction type. When configured for
step type 0, there are four extra parameters that determine the exact
timing of the step and direction signals. In the following figure
the meaning of these parameters is shown. The
parameters are in nanoseconds, but will be rounded up to an integer
multiple of the thread period for the threaed that calls
'make_pulses()'. For example, if 'make_pulses()' is called every 16 µs,
and steplen is 20000, then the step pulses will
be 2 x 16 = 32 µs long. The default value for all four of the parameters
is 1ns, but the automatic rounding takes effect the first time the code
runs. Since one step requires 'steplen' ns high and 'stepspace' ns
low, the maximum frequency is 1,000,000,000 divided by
'(steplen+stepspace)'. If 'maxfreq' is set higher than that limit, it
will be lowered automatically. If
maxfreq is zero, it will remain zero, but the output frequency will
still be limited.

When using the parallel port driver the step frequency can be doubled using
the <<sub:parport-functions,parport reset>> function together with stepgen's
'doublefreq' setting.

[[fig:stepdir-timing]]
.Step and Direction Timing
image::images/stepgen-type0.png[align="center"]

.Step Type 1

Step type 1 has two outputs, up and down. Pulses appear on one or the
other, depending on the direction of travel. Each pulse is 'steplen' ns
long, and the pulses are separated by at least 'stepspace' ns. The
maximum frequency is the same as for step type 0. If 'maxfreq' is set
higher than the limit it will be lowered. If 'maxfreq' is zero, it
will remain zero but the output frequency will still be
limited.

[WARNING]
Do not use the parport reset function with step types 2 - 14. Unexpected
results can happen.

.Step Type 2 - 14

Step types 2 through 14 are state based, and have from two to five
outputs. On each step, a state counter is incremented or decremented.
The Two-and-Three-Phase, Four-Phase, and Five-Phase show the output
patterns as a function of the state counter. The maximum frequency is
1,000,000,000 divided by 'steplen', and as in the other modes, 'maxfreq'
will be lowered if it is above the limit.

.Two-and-Three-Phase Step Types(((Two and Three Phase)))
image::images/stepgen-type2-4.png["Step Types: Two-and-Three-Phase",align="center"]

.Four-Phase Step Types(((Four Phase)))
image::images/stepgen-type5-10.png["Step Types: Four-Phase",align="center"]

.Five-Phase Step Types(((Five Phase)))
image::images/stepgen-type11-14.png["Step Types: Five-Phase",align="center"]

[[sub:stepgen-functions]]
=== Functions(((Hal stepgen Functions)))

The component exports three functions. Each function acts on all of
the step pulse generators - running different generators in different
threads is not supported.

* '(funct) stepgen.make-pulses' - High speed function to generate
  and count pulses (no floating point).
* '(funct) stepgen.update-freq' - Low speed function does position
  to velocity conversion, scaling and limiting.
* '(funct) stepgen.capture-position' - Low speed function for
  feedback, updates latches and scales position.

The high speed function 'stepgen.make-pulses' should be run in a very
fast thread, from 10 to 50 µs depending on the
capabilities of the computer. That thread's period determines the
maximum step frequency, since 'steplen', 'stepspace', 'dirsetup',
'dirhold', and 'dirdelay' are all rounded up to a integer multiple of
the thread periond in
nanoseconds. The other two functions can be called at a much lower
rate.

[[sec:pwmgen]]
== PWMgen(((PWMgen)))

This component provides software based generation of PWM (Pulse Width
Modulation) and PDM (Pulse Density Modulation) waveforms. It is a
realtime component only, and depending on CPU speed, etc, is capable of
PWM frequencies from a few hundred Hertz at pretty good resolution, to
perhaps 10 kHz with limited resolution.

.Loading PWMgen
----
loadrt pwmgen output_type=<config-array>
----

The '<config-array>' is a series of comma separated decimal integers. Each
number causes a single PWM generator to be loaded, the value of the number
determines the output type. The following example will install three PWM
generators. There is no default value, if '<config-array>' is not specified,
no PWM generators will be installed. The maximum number of frequency generators
is 8 (as defined by MAX_CHAN in pwmgen.c). Each generator is independent,
but all are updated by the same function(s) at the same time. In the following
descriptions, '<chan>' is the number of a specific generator. The first
generator is number 0.

.Loading PWMgen Example
----
loadrt pwmgen output_type=0,1,2
----

Will install three PWM generators. The first will use an output of
type _0_ (PWM only), the next one will use a type 1 output (PWM and direction)
and the third will use a type 2 output (UP and DOWN). There is no default
value, if _<config-array>_ is not not specified, no PWM generator will
be installed. The maximum number of frequency generators is 8 (as defined
by MAX_CHAN in pwmgen.c). Each generator is independent, but all are
updated by the same function(s), at the same time. In the descriptions
that follow, _<chan>_ is the number of specific generators. The numbering of
PWM generators starts at 0.

.Unloading PWMgen
----
unloadrt pwmgen
----

=== Output Types

The PWM generator supports three different 'output types'.

* 'Output type 0' - PWM output pin only. Only positive commands are accepted,
  negative values are treated as zero (and will be affected by the parameter
  'min-dc' if it is non-zero).
* 'Output type 1' - PWM/PDM and direction pins. Positive and negative inputs
  will be output as positive and negative PWM. The direction pin is false
  for positive commands, and true for negative commands. If your control
  needs positive PWM for both CW and CCW use the link:../man/man9/abs.9.html[abs] component
  to convert your PWM signal to positive value when a negative input is input.
* 'Output type 2' - UP and DOWN pins. For positive commands, the PWM signal
  appears on the up output, and the down output remains false. For negative
  commands, the PWM signal appears on the down output, and the up output
  remains false. Output type 2 is suitable for driving most H-bridges.

=== Pins

Each PWM generator will have the following pins:

* '(float) pwmgen.<chan>.value' - Command value, in arbitrary units.
  Will be scaled by the 'scale' parameter (see below).
* '(bit) pwmgen.<chan>.enable' - Enables or disables the PWM
  generator outputs.

Each PWM generator will also have some of these pins, depending on the
output type selected:

* '(bit) pwmgen.<chan>.pwm' - PWM (or PDM) output, (output types 0
  and 1 only).
* '(bit) pwmgen.<chan>.dir' - Direction output (output type 1 only).
* '(bit) pwmgen.<chan>.up' - PWM/PDM output for positive input value
  (output type 2 only).
* '(bit) pwmgen.<chan>.down' - PWM/PDM output for negative input value
  (output type 2 only).

=== Parameters

* '(float) pwmgen.<chan>.scale' - Scaling factor to convert 'value'
  from arbitrary units to duty cycle. For example if scale is set to 4000
  and the input value passed to the pwmgen.<chan>.value is 4000 then it will
  be 100% duty-cycle (always on). If the value is 2000 then it will be a 50%
  25 Hz square wave.
* '(float) pwmgen.<chan>.pwm-freq' - Desired PWM frequency, in Hz.
  If 0.0, generates PDM instead of PWM. If set higher than internal limits,
  next call of 'update_freq()' will set it to the internal limit. If non-zero,
  and 'dither' is false, next call of 'update_freq()' will set it to the
  nearest integer multiple of the 'make_pulses()' function period.
* '(bit) pwmgen.<chan>.dither-pwm' - If true, enables dithering to
  achieve average PWM frequencies or
  duty cycles that are unobtainable with pure PWM. If false, both the PWM
  frequency and the duty cycle will be rounded to values that can be
  achieved exactly.
* '(float) pwmgen.<chan>.min-dc' - Minimum duty cycle, between 0.0
  and 1.0 (duty cycle will go to
  zero when disabled, regardless of this setting).
* '(float) pwmgen.<chan>.max-dc' - Maximum duty cycle, between 0.0
  and 1.0.
* '(float) pwmgen.<chan>.curr-dc' - Current duty cycle - after all
  limiting and rounding (read only).

=== Functions

The component exports two functions. Each function acts on all of the
PWM generators - running different generators in different threads is
not supported.

* '(funct) pwmgen.make-pulses' - High speed function to generate PWM waveforms
  (no floating point). The high speed function 'pwmgen.make-pulses' should be
  run in the base (fastest) thread, from 10 to 50 µs depending on the
  capabilities of the computer. That thread's period determines the maximum PWM
  carrier frequency, as well as the resolution of the PWM or PDM signals. If
  the base thread is 50,000nS then every 50uS the module decides if it is time
  to change the state of the output. At 50% duty cycle and 25 Hz PWM frequency
  this means that the output changes state every (1 / 25) seconds / 50uS * 50% = 400
  iterations. This also means that you have a 800 possible duty cycle
  values (without dithering)
* '(funct) pwmgen.update' - Low speed function to scale and limit value and
  handle other parameters. This is the function of the module that does the
  more complicated mathematics to work out how many base-periods the output
  should be high for, and how many it should be low for.

[[sec:encoder]]
== Encoder(((encoder)))

This component provides software based counting of signals from
quadrature (or single-pulse) encoders. It is a realtime component only,
and depending on CPU speed, latency, etc, is capable of maximum count
rates of 10 kHz to perhaps up to 50 kHz.

The base thread should be 1/2 count speed to allow for noise and timing
variation. For example if you have a 100 pulse per revolution encoder on the
spindle and your maximum RPM is 3000 the maximum base thread should be 25 µs.
A 100 pulse per revolution encoder will have 400 counts. The spindle speed
of 3000 RPM = 50 RPS (revolutions per second). 400 * 50 = 20,000 counts per
second or 50 µs between counts.

The Encoder Counter Block Diagram is a block diagram of one channel of an
encoder counter.

[[fig:encoder-block-diagram]]
.Encoder Counter Block Diagram(((Encoder Block Diagram)))
image::images/encoder-block-diag.png[align="center"]

.Loading Encoder
----
halcmd: loadrt encoder [num_chan=<counters>]
----

'<counters>' is the number of encoder counters that you want to
install. If 'numchan' is not specified, three counters will be
installed. The maximum
number of counters is 8 (as defined by MAX_CHAN in encoder.c). Each
counter is independent, but all are updated by the same function(s) at
the same time. In the following descriptions, '<chan>' is the number
of a specific counter. The first counter is number 0.

.Unloading Encoder
----
halcmd: unloadrt encoder
----

=== Pins

* 'encoder.<chan>.counter-mode' (bit, I/O) (default: FALSE) - Enables
  counter mode. When true, the
  counter counts each rising edge of the phase-A input, ignoring the
  value on phase-B. This is useful for counting the output of a single
  channel (non-quadrature) sensor. When false, it counts in quadrature
  mode.
* 'encoder.<chan>.missing-teeth' (s32, In) (default: 0) - Enables the use
  of missing-tooth index. This allows a single IO pin to provide both
  position and index information. If the encoder wheel has 58 teeth with
  two missing, spaced as if there were 60(common for automotive crank
  sensors) then the position-scale should be set to 60 and
  missing-teeth to 2. To use this mode counter-mode should be set
  true. This mode will work for lathe threading but not for rigid
  tapping.
* 'encoder.<chan>.counts' (s32, Out) - Position in encoder counts.
* 'encoder.<chan>.counts-latched' (s32, Out) - Not used at this time.
* 'encoder.<chan>.index-enable' (bit, I/O) - When True, 'counts' and
  'position are' reset to zero on next rising edge of Phase Z. +
  At the
  same time, 'index-enable' is reset to zero to indicate that the rising
  edge has occurred. The 'index-enable' pin is bi-directional. If
  'index-enable' is False, the Phase Z channel of the encoder will be
  ignored, and the
  counter will count normally. The encoder driver will never set
  'index-enable' True. However, some other component may do so.
* 'encoder.<chan>.latch-falling' (bit, In) (default: TRUE) - Not used
  at this time.
* 'encoder.<chan>.latch-input' (bit, In) (default: TRUE) - Not used at
  this time.
* 'encoder.<chan>.latch-rising' (bit, In) - Not used at this time.
* 'encoder.<chan>.min-speed-estimate' (float, in) - Determine the
  minimum true velocity magnitude at which
  velocity will be estimated as nonzero and position-interpolated will
  be interpolated. The units of 'min-speed-estimate' are the same as the
  units of 'velocity' . Scale factor, in counts per length unit. Setting
  this parameter too
  low will cause it to take a long time for velocity to go to 0 after
  encoder pulses have stopped arriving.
* 'encoder.<chan>.phase-A' (bit, In) - Phase A of the quadrature encoder signal.
* 'encoder.<chan>.phase-B' (bit, In) - Phase B of the quadrature encoder signal.
* 'encoder.<chan>.phase-Z' (bit, In) - Phase Z (index pulse) of the quadrature encoder signal.
* 'encoder.<chan>.position' (float, Out) - Position in scaled units (see 'position-scale').
* 'encoder.<chan>.position-interpolated' (float, Out) - Position in
  scaled units, interpolated between encoder counts. +
  The 'position-interpolated' attempts to interpolate
  between encoder counts, based on the most
  recently measured velocity. Only valid when velocity is approximately
  constant and above 'min-speed-estimate'. Do not use for position
  control, since its value is incorrect at
  low speeds, during direction reversals, and during speed changes. +
  However, it allows a low ppr encoder (including a one pulse per
  revolution 'encoder') to be used for lathe threading, and may have
  other uses as well.
* 'encoder.<chan>.position-latched (float, Out)' - Not used at this time.
* 'encoder.<chan>.position-scale (float, I/O)' - Scale factor, in
  counts per length unit. For example, if
  position-scale is 500, then 1000 counts of the encoder will be reported
  as a position of 2.0 units.
* 'encoder.<chan>.rawcounts (s32, In)' - The raw count, as determined
  by update-counters. This value is
  updated more frequently than counts and position. It is also unaffected
  by reset or the index pulse.
* 'encoder.<chan>.reset' (bit, In) - When True, force 'counts' and
  'position' to zero immediately.
* 'encoder.<chan>.velocity' (float, Out) - Velocity in scaled units per
  second. 'encoder' uses an algorithm that greatly reduces quantization
  noise as compared
  to simply differentiating the 'position' output. When the magnitude
  of the true velocity is below
  min-speed-estimate, the velocity output is 0.
* 'encoder.<chan>.x4-mode (bit, I/O) (default: TRUE)' - Enables
  times-4 mode. When true, the counter counts each edge of
  the quadrature waveform (four counts per full cycle). When false, it
  only counts once per full cycle. In counter-mode, this parameter is
  ignored. The 1x mode is useful for some jogwheels.

=== Parameters

* 'encoder.<chan>.capture-position.time (s32, RO)'
* 'encoder.<chan>.capture-position.tmax (s32, RW)'
* 'encoder.<chan>.update-counters.time (s32, RO)'
* 'encoder.<chan>.update-counter.tmax (s32, RW)'

=== Functions

The component exports two functions. Each function acts on all of the
encoder counters - running different counters in different threads is
not supported.

* '(funct) encoder.update-counters' - High speed function to count
  pulses (no floating point).
* '(funct) encoder.capture-position' - Low speed function to update
  latches and scale position.

[[sec:pid]]
== PID(((PID)))

This component provides Proportional/Integral/Derivative control
loops. It is a realtime component only. For simplicity, this discussion
assumes that we are talking about position loops, however this
component can be used to implement other feedback loops such as speed,
torch height, temperature, etc. The PID Loop Block Diagram is a
block diagram of a single PID loop.

[[fig:pid-block-diag]]
.PID Loop Block Diagram(((PID Block Diagram)))
image::images/pid-block-diag.png[align="center"]

.Loading PID
----
halcmd: loadrt pid [num_chan=<loops>] [debug=1]
----

'<loops>' is the number of PID loops that you want to install. If
'numchan' is not specified, one loop will be installed. The maximum
number of
loops is 16 (as defined by MAX_CHAN in pid.c). Each loop is completely
independent. In the following descriptions, '<loopnum>' is the loop
number of a specific loop. The first loop is number 0.

If 'debug=1' is specified, the component will export a few extra
pins that
may be useful during debugging and tuning. By default, the extra
pins are not exported, to save shared memory space and avoid
cluttering the pin list.

.Unloading PID
----
halcmd: unloadrt pid
----

=== Pins

The three most important pins are

* '(float) pid.<loopnum>.command' - The desired position, as
  commanded by another system component.
* '(float) pid.<loopnum>.feedback' - The present position, as
  measured by a feedback device such as an encoder.
* '(float) pid.<loopnum>.output' - A velocity command that attempts
  to move from the present position to the desired position.

For a position loop, 'command' and 'feedback' are in position units.
For a linear axis, this could be inches, mm, meters, or whatever is
relevant. Likewise, for an angular axis, it could be degrees, radians,
etc. The units of the 'output' pin represent the change needed to make
the feedback match the command. As such, for a position loop 'Output'
is a velocity, in inches/sec, mm/sec, degrees/sec, etc. Time units are
always seconds, and the velocity units match the position units. If
command and feedback are in meters, then output is in meters per
second.

Each loop has two pins which are used to monitor or control the
general operation of the component.

* '(float) pid._<loopnum>_.error' - Equals '.command' minus '.feedback'.
* '(bit) pid._<loopnum>_.enable' - A bit that enables the loop. If
  '.enable' is false, all integrators are reset, and the output is
  forced to zero. If '.enable' is true, the loop operates normally.

Pins used to report saturation. Saturation occurs when the output of
the PID block is at its maximum or minimum limit.

* '(bit) pid._<loopnum>_.saturated' - True when output is saturated.
* '(float) pid._<loopnum>_.saturated_s' - The time the output has been saturated.
* '(s32) pid._<loopnum>_.saturated_count' - The time the output has been saturated.

The PID gains, limits, and other 'tunable' features of the loop are
available as pins so that they can be adjusted dynamically for more
advanced tuning possibilities.

* '(float) pid._<loopnum>_.Pgain' - Proportional gain
* '(float) pid._<loopnum>_.Igain' - Integral gain
* '(float) pid._<loopnum>_.Dgain' - Derivative gain
* '(float) pid._<loopnum>_.bias' - Constant offset on output
* '(float) pid._<loopnum>_.FF0' - Zeroth order feedforward - output
  proportional to command (position).
* '(float) pid._<loopnum>_.FF1' - First order feedforward - output
  proportional to derivative of command (velocity).
* '(float) pid._<loopnum>_.FF2' - Second order feedforward - output
  proportional to 2^nd^ derivative
  of command (acceleration).
* '(float) pid._<loopnum>_.deadband' - Amount of error that will be ignored
* '(float) pid._<loopnum>_.maxerror' - Limit on error
* '(float) pid._<loopnum>_.maxerrorI' - Limit on error integrator
* '(float) pid._<loopnum>_.maxerrorD' - Limit on error derivative
* '(float) pid._<loopnum>_.maxcmdD' - Limit on command derivative
* '(float) pid._<loopnum>_.maxcmdDD' - Limit on command 2^nd^ derivative
* '(float) pid._<loopnum>_.maxoutput' - Limit on output value

All _max*_ limits are implemented so that if the value of this parameter
is zero, there is no limit.

If 'debug=1' was specified when the component was installed, four
additional pins will be exported:

* '(float) pid._<loopnum>_.errorI' - Integral of error.
* '(float) pid._<loopnum>_.errorD' - Derivative of error.
* '(float) pid._<loopnum>_.commandD' - Derivative of the command.
* '(float) pid._<loopnum>_.commandDD' - 2^nd^ derivative of the command.

=== Functions

The component exports one function for each PID loop. This function
performs all the calculations needed for the loop. Since each loop has
its own function, individual loops can be included in different threads
and execute at different rates.

* '(funct) pid._<loopnum>_.do_pid_calcs' - Performs all calculations
  for a single PID loop.

If you want to understand the exact algorithm used to compute the
output of the PID loop, refer to figure <<fig:pid-block-diag,PID Loop Block Diagram>>, the
comments at the beginning of 'emc2/src/hal/components/pid.c' , and of
course to the code itself. The loop calculations are in the C
function 'calc_pid()'.

[[sec:simulated-encoder]]
== Simulated Encoder(((Simulated Encoder)))

The simulated encoder is exactly that. It produces quadrature pulses
with an index pulse, at a speed controlled by a HAL pin. Mostly useful
for testing.

.Loading sim-encoder
----
halcmd: loadrt sim-encoder num_chan=<number>
----

'<number>' is the number of encoders that you want to simulate. If not
specified, one encoder will be installed. The maximum number is 8 (as
defined by MAX_CHAN in sim_encoder.c).

.Unloading sim-encoder
----
halcmd: unloadrt sim-encoder
----

=== Pins

* '(float) sim-encoder._<chan-num>_.speed' - The speed command for the
  simulated shaft.
* '(bit) sim-encoder._<chan-num>_.phase-A' - Quadrature output.
* '(bit) sim-encoder._<chan-num>_.phase-B' - Quadrature output.
* '(bit) sim-encoder._<chan-num>_.phase-Z' - Index pulse output.

When '.speed' is positive, '.phase-A' leads '.phase-B'.

=== Parameters

* '(u32) sim-encoder._<chan-num>_.ppr' - Pulses Per Revolution.
* '(float) sim-encoder._<chan-num>_.scale' - Scale Factor for 'speed'.
  The default is 1.0, which means that 'speed' is in revolutions per
  second. Change to 60 for RPM, to 360 for
  degrees per second, 6.283185 for radians per seconed, etc.

Note that pulses per revolution is not the same as counts per
revolution. A pulse is a complete quadrature cycle. Most encoder
counters will count four times during one complete cycle.

=== Functions

The component exports two functions. Each function affects all
simulated encoders.

* '(funct) sim-encoder.make-pulses' - High speed function to
  generate quadrature pulses (no floating point).
* '(funct) sim-encoder.update-speed' - Low speed function to read
  'speed', do scaling, and set up 'make-pulses'.

[[sec:debounce]]
== Debounce(((debounce)))

Debounce is a realtime component that can filter the glitches created
by mechanical switch contacts. It may also be useful in other
applications where short pulses are to be rejected.

.Loading debounce
----
halcmd: loadrt debounce cfg=<config-string>
----

<config-string>:: Is a series of comma separated decimal integers.
  Each number installs
  a group of identical debounce filters, the number determines how many
  filters are in the group.

.Loading debounce Example
----
halcmd: loadrt debounce cfg=1,4,2
----

will install three groups of filters. Group 0 contains one filter,
group 1 contains four, and group 2 contains two filters. The default
value for '<config-string>' is '"1"' which will install a single group
containing a single filter. The
maximum number of groups 8 (as defined by MAX_GROUPS in debounce.c).
The maximum number of filters in a group is limited only by shared
memory space. Each group is completely independent. All filters in a
single group are identical, and they are all updated by the same
function at the same time. In the following descriptions, '<G>' is the
group number and '<F>' is the filter number within the group. The
first filter is group 0,
filter 0.

.Unloading debounce
----
halcmd: unloadrt debounce
----

=== Pins

Each individual filter has two pins.

* '(bit) debounce._<G>_._<F>_.in' - Input of filter _<F>_ in group _<G>_.
* '(bit) debounce._<G>_._<F>_.out' - Output of filter _<F>_ in group _<G>_.

=== Parameters

Each group of filters has one parameterfootnote:[Each individual
filter also has an internal state variable. There is a
compile time switch that can export that variable as a parameter. This
is intended for testing, and simply wastes shared memory under normal
circumstances.].

* '(s32) debounce._<G>_.delay' - Filter delay for all filters in group _<G>_.

The filter delay is in units of thread periods. The minimum delay is
zero. The output of a zero delay filter exactly follows its input - it
doesn't filter anything. As 'delay' increases, longer and longer
glitches are rejected. If 'delay' is 4, all glitches less than or
equal to four thread periods will be rejected.

=== Functions

Each group of filters has one function, which updates all the filters
in that group 'simultaneously'. Different groups of filters can be
updated from different threads at different periods.

* '(funct) debounce._<G>_' - Updates all filters in group _<G>_.

[[sec:siggen]]
== Siggen(((Siggen)))

Siggen is a realtime component that generates square, triangle, and
sine waves. It is primarily used for testing.

.Loading siggen
----
halcmd: loadrt siggen [num_chan=<chans>]
----

<chans>:: is the number of signal generators that you want to install.
  If 'numchan' is not specified, one signal generator will be installed.
  The maximum
  number of generators is 16 (as defined by MAX_CHAN in siggen.c). Each
  generator is completely independent. In the following descriptions is
<chan>:: the number of a specific signal generator (the numbers
  start at 0).

.Unloading siggen
----
halcmd: unloadrt siggen
----

=== Pins

Each generator has five output pins.

* '(float) siggen._<chan>_.sine' - Sine wave output.
* '(float) siggen._<chan>_.cosine' - Cosine output.
* '(float) siggen._<chan>_.sawtooth' - Sawtooth output.
* '(float) siggen._<chan>_.triangle' - Triangle wave output.
* '(float) siggen._<chan>_.square' - Square wave output.

All five outputs have the same frequency, amplitude, and offset.

In addition to the output pins, there are three control pins:

* '(float) siggen._:<chan>_.frequency' - Sets the frequency in Hertz,
  default value is 1 Hz.
* '(float) siggen._<chan>_.amplitude' - Sets the peak amplitude of the
  output waveforms, default is 1.
* '(float) siggen._<chan>_.offset' - Sets DC offset of the output
  waveforms, default is 0.

For example, if 'siggen.0.amplitude' is 1.0 and 'siggen.0.offset' is
0.0, the outputs will swing from -1.0 to +1.0. If 'siggen.0.amplitude'
is 2.5 and 'siggen.0.offset' is 10.0, then the outputs will swing from
7.5 to 12.5.

=== Parameters

None. footnote:[Prior to version 2.1, frequency, amplitude, and offset
were parameters. They were changed to pins to allow control by other
components.]

=== Functions

* '(funct) siggen._<chan>_.update' - Calculates new values for all five outputs.

[[sec:lut5]]
== lut5(((lut5)))

The lut5 component is a 5 input logic component based on a look up table.

* 'lut5' does not require a floating point thread.

.Loading lut5
----
loadrt lut5 [count=N|names=name1[,name2...]]
addf lut5.N servo-thread | base-thread
setp lut5.N.function 0xN
----

.Lut5 Computing Function
To compute the hexadecimal number for the function starting from the top put
a 1 or 0 to indicate if that row would be true or false. Next write down every
number in the output column starting from the top and writing them from right
to left. This will be the binary number. Using a calculator with a program
view like the one in Ubuntu enter the binary number and then convert it to
hexadecimal and that will be the value for function.

.Lut5 Look Up Table
[width="50%",cols="6*^",options="header"]
|===
|Bit 4|Bit 3|Bit 2|Bit 1|Bit 0|Output
|0|0|0|0|0|
|0|0|0|0|1|
|0|0|0|1|0|
|0|0|0|1|1|
|0|0|1|0|0|
|0|0|1|0|1|
|0|0|1|1|0|
|0|0|1|1|1|
|0|1|0|0|0|
|0|1|0|0|1|
|0|1|0|1|0|
|0|1|0|1|1|
|0|1|1|0|0|
|0|1|1|0|1|
|0|1|1|1|0|
|0|1|1|1|1|
|1|0|0|0|0|
|1|0|0|0|1|
|1|0|0|1|0|
|1|0|0|1|1|
|1|0|1|0|0|
|1|0|1|0|1|
|1|0|1|1|0|
|1|0|1|1|1|
|1|1|0|0|0|
|1|1|0|0|1|
|1|1|0|1|0|
|1|1|0|1|1|
|1|1|1|0|0|
|1|1|1|0|1|
|1|1|1|1|0|
|1|1|1|1|1|
|===

.Lut5 Two Inputs Example
In the following table we have selected the output state for each line
that we wish to be true.

.Lut5 Two Inputs Example Look Up Table
[width="50%",cols="6*^",options="header"]
|===
|Bit 4|Bit 3|Bit 2|Bit 1|Bit 0|Output
|0|0|0|0|0|0
|0|0|0|0|1|1
|0|0|0|1|0|0
|0|0|0|1|1|1
|===

Looking at the output column of our example we want the output to be on
when Bit 0 or Bit 0 and Bit1 is on and nothing else. The binary number is
'b1010' (rotate the output 90 degrees CW). Enter this number into the
calculator then change the display to hexadecimal and the number needed for
function is '0xa'. The hexadecimal prefix is '0x'.

// vim: set syntax=asciidoc:
