general_ref.lyx

CNC 的开放码,EMC2 V2.2.8版

\begin_inset LatexCommand \label{sec:CanonDigOut}

\end_inset 

Digital Output
\layout Standard

The canonical digital output (I/O type field: 
\family typewriter 
\series bold 
digout
\family default 
\series default 
) is also very simple.
\layout Subsection

Pins
\layout Itemize


\shape smallcaps 
(bit)
\shape default 
 
\family typewriter 
\series bold 
out
\family default 
\series default 
 -- Value to be written (possibly inverted) to the hardware output.
\layout Subsection

Parameters
\layout Itemize


\shape smallcaps 
(bit)
\shape default 
 
\family typewriter 
\series bold 
invert
\family default 
\series default 
 -- If TRUE, 
\family typewriter 
\series bold 
out
\family default 
\series default 
 is inverted before writing to the hardware.
\layout Subsection

Functions
\layout Itemize


\shape smallcaps 
(funct)
\shape default 
 
\family typewriter 
\series bold 
write
\family default 
\series default 
 -- Read 
\family typewriter 
\series bold 
out
\family default 
\series default 
 and 
\family typewriter 
\series bold 
invert
\family default 
\series default 
, and set hardware output accordingly.
\layout Section

Analog Input
\layout Standard

The canonical analog input (I/O type: 
\family typewriter 
\series bold 
adcin
\family default 
\series default 
).
 This is expected to be used for analog to digital converters, which convert
 e.g.
 voltage to a continuous range of values.
\layout Subsection

Pins
\layout Itemize

(
\shape smallcaps 
float
\shape default 
) 
\series bold 
value
\series default 
 -- The hardware reading, scaled according to the 
\series bold 
scale
\series default 
 and 
\series bold 
offset
\series default 
 parameters.
 
\series bold 
Value
\series default 
 = ((input reading, in hardware-dependent units) * 
\series bold 
scale
\series default 
) - 
\series bold 
offset
\layout Subsection

Parameters
\layout Itemize

(
\shape smallcaps 
float
\shape default 
) 
\series bold 
scale
\series default 
 -- The input voltage (or current) will be multiplied by 
\series bold 
scale
\series default 
 before being output to 
\series bold 
value
\series default 
.
\layout Itemize

(
\shape smallcaps 
float
\shape default 
) 
\series bold 
offset
\series default 
 -- This will be subtracted from the hardware input voltage (or current)
 after the scale multiplier has been applied.
\layout Itemize

(
\shape smallcaps 
float
\shape default 
) 
\series bold 
bit_weight
\series default 
 -- The value of one least significant bit (LSB).
 This is effectively the granularity of the input reading.
\layout Itemize

(
\shape smallcaps 
float
\shape default 
) 
\series bold 
hw_offset
\series default 
 -- The value present on the input when 0 volts is applied to the input
 pin(s).
\layout Subsection

Functions
\layout Itemize

(
\shape smallcaps 
funct
\shape default 
) 
\series bold 
read
\series default 
 -- Read the values of this analog input channel.
 This may be used for individual channel reads, or it may cause all channels
 to be read
\layout Section

Analog Output
\layout Standard

The canonical analog output (I/O Type: 
\family typewriter 
\series bold 
adcout
\family default 
\series default 
).
 This is intended for any kind of hardware that can output a more-or-less
 continuous range of values.
 Examples are digital to analog converters or PWM generators.
\layout Subsection*

Pins
\layout Itemize

(
\shape smallcaps 
float
\shape default 
) 
\series bold 
value
\series default 
 -- The value to be written.
 The actual value output to the hardware will depend on the scale and offset
 parameters.
\layout Itemize

(
\shape smallcaps 
bit
\shape default 
) 
\series bold 
enable
\series default 
 -- If false, then output 0 to the hardware, regardless of the 
\series bold 
value
\series default 
 pin.
\layout Subsection

Parameters
\layout Itemize

(
\shape smallcaps 
float
\shape default 
) 
\series bold 
offset
\series default 
 -- This will be added to the 
\series bold 
value
\series default 
 before the hardware is updated
\layout Itemize

(
\shape smallcaps 
float
\shape default 
) 
\series bold 
scale
\series default 
 -- This should be set so that an input of 1 on the 
\series bold 
value
\series default 
 pin will cause 1V 
\layout Itemize

(
\shape smallcaps 
float
\shape default 
) 
\series bold 
high_limit
\series default 
 (optional) -- When calculating the value to output to the hardware, if
 
\series bold 
value
\series default 
 + 
\series bold 
offset
\series default 
 is greater than 
\series bold 
high_limit
\series default 
, then 
\series bold 
high_limit
\series default 
 will be used instead.
\layout Itemize

(
\shape smallcaps 
float
\shape default 
) 
\series bold 
low_limit
\series default 
 (optional) -- When calculating the value to output to the hardware, if
 
\series bold 
value
\series default 
 + 
\series bold 
offset
\series default 
 is less than 
\series bold 
low_limit
\series default 
, then 
\series bold 
low_limit
\series default 
 will be used instead.
\layout Itemize

(
\shape smallcaps 
float
\shape default 
) 
\series bold 
bit_weight
\series default 
 (optional) -- The value of one least significant bit (LSB), in volts (or
 mA, for current outputs)
\layout Itemize

(
\shape smallcaps 
float
\shape default 
) 
\series bold 
hw_offset
\series default 
 (optional) -- The actual voltage (or current) that will be output if 0
 is written to the hardware.
\layout Subsection

Functions
\layout Standard

(
\shape smallcaps 
funct
\shape default 
) 
\series bold 
write
\series default 
 -- This causes the calculated value to be output to the hardware.
 If enable is false, then the output will be 0, regardles of 
\series bold 
value
\series default 
, 
\series bold 
scale
\series default 
, and 
\series bold 
offset
\series default 
.
 The meaning of 
\begin_inset Quotes eld
\end_inset 

0
\begin_inset Quotes erd
\end_inset 

 is dependent on the hardware.
 For example, a bipolar 12-bit A/D may need to write 0x1FF (mid scale) to
 the D/A get 0 volts from the hardware pin.
 If enable is true, read scale, offset and value and output to the adc (
\series bold 
scale
\series default 
 * 
\series bold 
value
\series default 
) + 
\series bold 
offset
\series default 
.
 If enable is false, then output 0.
\layout Section


\begin_inset LatexCommand \label{sec:CanonEncoder}

\end_inset 

Encoder
\layout Standard

The canonical encoder interface (I/O type field:
\family typewriter 
\series bold 
 encoder
\family default 
\series default 
 ) provides the functionality needed for homing to an index pulse and doing
 spindle synchronization, as well as basic position and/or velocity control.
 This interface should be implementable regardless of the actual underlying
 hardware, although some hardware will provide 
\begin_inset Quotes eld
\end_inset 

better
\begin_inset Quotes erd
\end_inset 

 results.
 (For example, capture the index position to +/- 1 count while moving faster,
 or have less jitter on the velocity pin.)
\layout Subsection

Pins
\layout Itemize


\shape smallcaps 
(s32)
\family typewriter 
\series bold 
\shape default 
 count
\family default 
\series default 
 -- Encoder value in counts.
\layout Itemize


\shape smallcaps 
(float)
\shape default 
 
\family typewriter 
\series bold 
position
\family default 
\series default 
 -- Encoder value in position units (see parameter 
\begin_inset Quotes eld
\end_inset 

scale
\begin_inset Quotes erd
\end_inset 

).
 
\layout Itemize


\shape smallcaps 
(float)
\shape default 
 
\family typewriter 
\series bold 
velocity
\family default 
\series default 
 -- Velocity in position units per second.
\layout Itemize


\shape smallcaps 
(bit)
\shape default 
 
\family typewriter 
\series bold 
reset
\family default 
\series default 
 -- When True, force counter to zero.
\layout Itemize


\shape smallcaps 
(bit)
\shape default 
 
\family typewriter 
\series bold 
index-enable
\family default 
\series default 
 -- (bidirectional) When True, reset to zero on next index pulse, and set
 pin False.
\layout Standard

The 
\begin_inset Quotes eld
\end_inset 

index-enable
\begin_inset Quotes erd
\end_inset 

 pin is bi-directional, and might require a little more explanation.
 If 
\begin_inset Quotes eld
\end_inset 

index-enable
\begin_inset Quotes erd
\end_inset 

 is False, the index channel of the encoder will be ignored, and the counter
 will count normally.
 The encoder driver will never set 
\begin_inset Quotes eld
\end_inset 

index-enable
\begin_inset Quotes erd
\end_inset 

 True.
 However, some other component may do so.
 If 
\begin_inset Quotes eld
\end_inset 

index-enable
\begin_inset Quotes erd
\end_inset 

 is True, then when the next index pulse arrives, the encoder counter will
 be reset to zero, and the driver will set 
\begin_inset Quotes eld
\end_inset 

index-enable
\begin_inset Quotes erd
\end_inset 

 False.
 That will let the other component know that an index pulse arrived.
 This is a form of handshaking - the other component sets 
\begin_inset Quotes eld
\end_inset 

index-enable
\begin_inset Quotes erd
\end_inset 

 True to request a index pulse reset, and the driver sets it False when
 the request has been satisfied.
\layout Subsection

Parameters
\layout Itemize


\shape smallcaps 
(float)
\shape default 
 
\family typewriter 
\series bold 
scale
\family default 
\series default 
 -- The scale factor used to convert counts to position units.
 It is in 
\begin_inset Quotes eld
\end_inset 

counts per position unit
\begin_inset Quotes erd
\end_inset 

.
 For example, if you have a 512 count per turn encoder on a 5 turn per inch
 screw, the scale should be 512*5 = 2560 counts per inch, which will result
 in 
\begin_inset Quotes eld
\end_inset 

position
\begin_inset Quotes erd
\end_inset 

 in inches and 
\begin_inset Quotes eld
\end_inset 

velocity
\begin_inset Quotes erd
\end_inset 

 in inches per second.
\layout Itemize


\shape smallcaps 
(float)
\shape default 
 
\family typewriter 
\series bold 
max-index-vel
\family default 
\series default 
 -- (optional) The maximum velocity (in position units per second) at which
 the encoder can reset on an index pulse with +/- 1 count accuracy.
 This is an output from the encoder driver, and is intended to tell the
 user something about the hardware capabilities.
 Some hardware can reset the counter at the exact moment the index pulse
 arrives.
 Other hardware can only tell that an index pulse arrived sometime since
 the last time the read function was called.
 For the latter, +/- 1 count accuracy can only be achieved if the encoder
 advances by 1 count or less between calls to the read function.
\layout Itemize


\shape smallcaps 
(float)
\shape default 
 
\family typewriter 
\series bold 
velocity-resolution
\family default 
\series default 
 -- (optional) The resolution of the velocity output, in position units
 per second.
 This is an output from the encoder driver, and is intended to tell the
 user something about the hardware capabilities.
 The simplest implementation of the velocity output is the change in postion
 from one call of the read function to the next, divided by the time between
 calls.
 This yields a rather coarse velocity signal that jitters back and forth
 between widely spaced possible values (quantization error).
 However, some hardware captures both the counts and the exact time when
 a count occurres (possibly with a very high resolution clock).
 That data allows the driver to calculate velocity with finer resolution
 and less jitter.
 
\layout Subsection

Functions
\layout Standard

There is only one function, to read the encoder(s).
 
\layout Itemize


\family typewriter 
\noun on 
(funct)
\noun default 
 
\series bold 
read
\family default 
\series default 
 -- Capture counts, update position and velocity.
\the_end