The lcec_el4xxx driver supports a
wide range of analog output devices and replaces a number of older
single-purpose drivers.
It currently supports 3 basic families of devices:
The EP4174 is somewhat unique in that it can be a -10..10V, 0..10V, 0..20mA, or 4..20mA device, and needs configuration settings to control this. At the moment this needs to be done by hand with SDO settings, but support will be added to this driver eventually.
This driver creates a large number of pins for each analog out device. Here’s an example from a EL4032, a 2-port device:
8 bit IN FALSE lcec.0.D19.aout-0-absmode
8 float OUT 0 lcec.0.D19.aout-0-curr-dc
8 bit IN FALSE lcec.0.D19.aout-0-enable
8 float I/O 1 lcec.0.D19.aout-0-max-dc
8 float I/O -1 lcec.0.D19.aout-0-min-dc
8 bit OUT FALSE lcec.0.D19.aout-0-neg
8 float I/O 0 lcec.0.D19.aout-0-offset
8 bit OUT FALSE lcec.0.D19.aout-0-pos
8 s32 OUT 0 lcec.0.D19.aout-0-raw
8 float I/O 1 lcec.0.D19.aout-0-scale
8 float IN 0 lcec.0.D19.aout-0-value
8 bit IN FALSE lcec.0.D19.aout-1-absmode
8 float OUT 0 lcec.0.D19.aout-1-curr-dc
8 bit IN FALSE lcec.0.D19.aout-1-enable
8 float I/O 1 lcec.0.D19.aout-1-max-dc
8 float I/O -1 lcec.0.D19.aout-1-min-dc
8 bit OUT FALSE lcec.0.D19.aout-1-neg
8 float I/O 0 lcec.0.D19.aout-1-offset
8 bit OUT FALSE lcec.0.D19.aout-1-pos
8 s32 OUT 0 lcec.0.D19.aout-1-raw
8 float I/O 1 lcec.0.D19.aout-1-scale
8 float IN 0 lcec.0.D19.aout-1-value
8 bit OUT TRUE lcec.0.D19.slave-online
8 bit OUT TRUE lcec.0.D19.slave-oper
8 bit OUT FALSE lcec.0.D19.slave-state-init
8 bit OUT TRUE lcec.0.D19.slave-state-op
8 bit OUT FALSE lcec.0.D19.slave-state-preop
8 bit OUT FALSE lcec.0.D19.slave-state-safeop
For each channel, the following pins are created:
absmode: If set, then the device’s output won’t be allowed to go
negative. Any attempt to output a negative value will be
interpreted as a positive value instead. That is, requesting -0.3
will result in +0.3 instead.enable: If false (default), then output on this port is disabled.
You must set enable to true before outputting anything.max-dc: The maximum duty cycle allowed for this port. Must be
between 1.0 and min-dc.min-dc: The minimum duty cycle allowed for this port. Must be
between -1.0 and max-dc.offset: Used to control the scaling between value and curr-dc (and hence raw). See below.scale: Used to control the scaling between value and curr-dc (and hence raw). See below.value: The requested output value. Should be between max-dc and
min-dc, unless offset or scale are set. See below.curr-dc: The current duty cycle for this device.neg: True if the current output value is negative.pos: True if the current output value is positive.raw: The raw value sent to the hardware; should be between -0x7fff and 0x7fff.value and raw.The device’s actual output is controlled by raw and curr_dc, which
are calculated as follows:
curr_dc = (value / scale) + offset
The value of curr_dc should range between -1 and +1, but can be restricted by min-dc and max-dc.
raw = curr_dc * max_value. For Beckhoff hardware, max_value is generally 0x7fff, or 32,767.
If scale is 1 (the default) and offset is 0, then setting value
to 0 leads to raw = (0/1 + 0) * 32767, which is 0. If value is
1, then the same math would give curr_dc = 1/1 + 0, or 1, and
then raw = 1 * 32767, which is 32767.
Suppose you have a spindle that takes a 0..10V input to control the spindle RPM. The maximum RPM is 25,000 RPM, but it loses torque as the speed slows and doesn’t support anything below 5,000 RPM, which happens at 2V. To disable the spindle entirely, the voltage needs to be turned off (set to 0V).
To accomplish this set scale=25000 and min_dc=0.2. This should
result in being able to set value=RPM directly:
If RPM=25000, then value=25000. Then curr_dc=25000/25000=1, so
raw=32767, which is the largest value allowed, which will result in
the hardware sending 10V. Any attempt to set RPM higher will just be
capped at 25000.
If RPM=3000 (which is below the 5,000 RPM limit mentioned above), then value=3000. Then curr_dc=3000/25000=0.120.
This is less than min_dc, so it will be bumped up to 0.2. That
will result in a raw value of 0.2*32767=6554, which should result
in around 2V, which will give 5,000 RPM.
To disable the spindle entirely, instead of setting RPM=0, just set
enable to false. That will drop the output to 0V.