On Monday, December 30, 2019 at 8:52:14 PM UTC-6, Aurelien wrote:
>
> off course i have tested the DAC output regardless to the MK settings but 
> from the cape pwm output
> 0v on the DAC input = -10v ouptut
> 24v on the DAC input = +10v outpur
> ~12v on the DAC input = 0v output
>
> Regards
>

You are missing an importance component in your setup. The component from 
Aliexpress  that you called "DAC" is a signal isolator (converter), and is 
not a DAC. You need a PWM DAC, which converts PWM signal to DC voltage and 
is placing between the PWM signal and the isolator's input.

see 
https://www.allaboutcircuits.com/technical-articles/low-pass-filter-a-pwm-signal-into-an-analog-voltage/

 As Justin has pointed out that when PWM=0V -> full motor reverse is 
undesirable. This is also somewhat dangerous as when prior components to 
the KBMG/Isolator (i.e. the BB or the cape) loss power, the motor would 
kick into a full speed mode.  A simple solution is a FWR/REV signal from BB 
as Justin has suggested, but need a different circuit and maybe a different 
isolator than the one you got. 

I would rethink the whole motor driving scheme starting with why motor 
reversing is needed, motor acceleration/deceleration requirements should be 
investigated, and what Gcodes are required to do the operation, and go from 
there with components selection and wiring.

-- 
website: http://www.machinekit.io blog: http://blog.machinekit.io github: 
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