So, you would normally have encoders feeding position information back to a hardware encoder counter, and an interface device sending the appropriate velocity command to a servo amplifiers of some type. Analog velocity servo amplifiers usually take a +/- 10 V analog velocity command,
PWM-input servo amps take a digital signal where pulse width is proportional to desired velocity, and step/dir servo drives tale signals just like stepper drives.
Most likely is is a signed analog value from -10 V to +10 V, zero volts would command zero velocity. But, some drives do use other ranges and scale factors. Yes, you would need a digital to analog converter to drive the servo amp. My PPMC interface, for instance, has a 16-bit DAC on it for each channel.Regarding the motors and drivers already on the machine, I'm not even sure of what type of input they take- it seems to be 0-5v analog signals correlated with the rpms- What interfaces would be used to give emc2 the ability to output analog values (or what interface can I expect to carry digital info to a D/A device) ?
That's my page, so it has some things specific to using my PWM-input servo amps with my Universal PWM Controller board (UPC). But, in general, there are several products from other vendors that do a very similar job. So, the servo amp drives the motor, and the UPC board counts encoder signals and genrates the PWM waveform for the amp. These are the things you need to control the servo motor. Halscope could be seeing essentially the same thing without any hardware at all other than the parallel port, although the encoder count rates would be limited by the software.what hardware is allowing for the "HAL oscope" on this page:
HalScope is a SOFTWARE oscilloscope, so it does not require any hardware, by ITSELF, to function. It can grab any HAL signal in the entire EMC2 system and display it in graphical form.
HAL is the language that connects many of the parts of EMC2. It connects the motion controller to whatever it is that makes motors move, so that the "upper parts" of EMC can completely ignore the details of how movement is achieved. It also allows a great deal of flexibility in how a machine is structured (although EMC1 had this capability before) so robots, Stewart platforms and Cartesian machine can be set up to be commanded in XYZ positions. It is also used to connect all the auxilliary I/O such as tool changers and special fixture operations from G-codes to hardware. There is quite a bit of detail in the integrators manual, I think.I'm seeing the hardware abstraction layer subject come up qhuite a lot but im falling short of understanding its role in the whole system's process... the wiki page doesnt seem to cover all that much of its capabilities...
someone mind simplifying how HAL is applied for me?
maybe hint at how it might help me get bytes out for analog conversion or something?
HAL won't help you "get bytes out for analog conversion" directly. You need a DAC and a driver for EMC2 for that DAC. Easiest is to use one that is already made for the purpose, with a driver already written for EMC2.