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eCAP Module for 4 Wire Stepper Motor Control in OMAP-l138

Subramanian R
Prodigy 30 points
Other Parts Discussed in Thread: OMAP-L138

Hi

We are trying to using Mity-DSP-138F SOM module to 4 wire Stepper Motor Control.

eHRPWM Module outputs, we are unable to use as SPI1 SCS0 is used as CS for NOR Flash. So we are left to eCAP Modules as APWM outputs. (has only 3 outputs).

Our Stepper motor is one with 4 lead Wires. Can I able to control it through eCAP Module? In OMAP-L138 Reference Manual, It is shown 4 APWM outputs controlling 4 outputs. Can we synchronize all 3 APWM outputs ? How to generate the 4 APWM output?

If this is not possible, Can we have on 1 eHRPWM outputs( 0A/0B)  and two eCAP APWM outputs synchronized for 4 wire Motor Control?

Thanks and Regards,

Subramanian

  • 0
    TI__Mastermind 35645 points

    Hi,

    Thanks for your post.

    Yes, ofcourse, we could synchronize all 3 APWM outputs. With conventionally derived PWM capabilities, we could generate 3 APWM outputs to the max. and the other 3 PWM outputs to be meant for high resolution PWM (HRPWM).

    In general, there are three PWM modules (EPWM0, EPWM1, EPWM2) and each PWM module of C6748 has two EPWMxA and EPWMxB output lines where x can be 0, 1 & 2.

    EHRPWM is implemented using the A signal path of PWM, that is, on the EPWMxA output. EPWMxB output has conventional PWM capabilities.

    I believe, you could generate 3 eCAP APWM outputs (B signal path, EPWMxB) and 1 eHRPWM output (A signal path, EPWMxA) to synchronize for 4 wire motor control. May be, in C6748 you chain multiple instances of EPWMx to connect multiple ePWM modules to generate multiple APWM outputs. Kindly check more details on the feasibility of 4 APWM outputs from the below information

    Please refer figures 17.1, 17.2, 17.3 and section 17.1.2 for more info. on ePWM submodule from the TRM below:

    http://www.ti.com/lit/ug/spruh77a/spruh77a.pdf

    Thanks & regards,

    Sivaraj K

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