Tom:

I'm using a plain jane 2 phase stepper on the 1st pair of what I presume are H bridge PWMs (I'll call it Side A) of the Snap Amp.

The brushless motor is going on the 2nd side (Side B) of the Snap Amp.

The instructions in the Snap Amp manual lead me to conclude that both axes 0 and 1 were being used for side A of the Snap Amp because they are blanked out in the table shown at the bottom of the 'Snap Amp connectors' webpage. I also figured the same was true for axes 1 and 2 for the BLDC.

I also don't understand why the instructions direct me to only assign channel 10 to the BLDC whereas for a stepper installed on 'Side B' the equivalent situation would call for the use of channels 10 and 11.

I guess it would be helpful for me to understand how things are getting assigned internally. I know how a stepper and how a 3 phase BLDC work in terms of commutating with half bridges or h bridges, including the deadtime used to prevent shoot-through, so I'm not a neophyte. If I knew how things are getting assigned in terms of outputchan0 and outputchan1 for each axis, and how each axis gets assigned to the snap Amp, then I can figure out what is going on "by first principles" without consulting a reference each and every time.

--- In DynoMotion@yahoogroups.com, Tom Kerekes <tk@...> wrote:
>
> Hi Erik,
>  
> You aren't being very clear about your situation.  How many motors do you have and what type are they?
>  
> A 3 phase brushless motor needs 2 PWMs.  So for a SnapAmp that would be either 8,9 or 10,11.   So set OutputChan0 to either 8 or 10 to select which side of the SnapAmp to use.  The OutputChan1 setting for the axis is not used in 3phase brushless mode as a consecutive pair of PWMs are required.
>  
> Axis channels are numbered starting with 0.  So the 2nd axis would be ch1
>  
> Output Mode would be "3PH Servo" for a 3phase brushless motor.
>  
> Regards
> TK
>
> From: quelisto <quelisto@...>
> To: DynoMotion@yahoogroups.com
> Sent: Tuesday, January 24, 2012 9:11 PM
> Subject: [DynoMotion] Snap amp and BLDCs
>
>
>  
> Hello Tom!
>
> I've got the Snap Amp you sent me last week. When I use the 2nd pair of PWMs for a brushless dc motor, how do I specify PWM channel 10 for axis 2? Is the following snippet of code correct?
>
> ch2->OutputChan0=10;
> ch2->OutputChan1=10;
>
> I am using axis 0 (and 1 implicitly, I presume) to run a stepper motor.
>
> Will this also mean axis 3 is being "used" by the Kflop to talk to the Snap Amp for the 2nd PWM pair?
>
> Furthermore, do I use STEP_DIR for Output mode?
>
> ch2->OutputMode=STEP_DIR_MODE;
>
> Thanks!
>
> -Erik-
>