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PROCESSOR-SDK-AM62X: Genearating PWM signals on AM62x SK at U-Boot Level

Murali Chikkanna
Prodigy 145 points
Part Number: PROCESSOR-SDK-AM62X

Hi,

I am to trying to generate PWM signals on EHRPWM Pin on  Am62x Starter kit at U-Boot Level. We can generate PWM signals at Kernel Level. Can we do the same on U-Boot. If possible,Kindly guide me through the process. 

  • 0
    TI__Guru 68630 points

    Hello,
    I'm not aware of Enhanced Pulse Width Modulation (EPWM) support in u-boot on AM62x.
    Best,
    -Hong

  • 0 in reply to Hong Guan64
    Prodigy 145 points

    Hi Hong,

    Thanks for the reply.

    I am trying to control EPWM registers using mw and md commands in uboot. 

    I have followed the steps as per the Technical reference Manual Am62x. As per the Table 12-2999. EPWMx Initialization.

    I have done done initialisation, but cant able to find any waveform on Pin EHRPWM1_B (E18).

    Steps followed to generate PWM Signals on U-Boot.

    Step 1: set E18 pin Am62x_sk.dts file as output:

     ehrpwm_pins_default: ehrpwm-pins-default {

    pinctrl-single,pins = <
    AM62X_IOPAD(0x1a0, PIN_OUTPUT, 6)     /* E18 */
    >;
    };
    Step 2:  Set EPW1_TBCLK ( CTRL_EPWM_TB_CLKEN Register):
                     => mw.w 0x00104130 0x2

    Step 3: Wrote 0x30h to register  EPWM_TBCTL_REG.

                => mw.w 0x23010000 0x30

    step 4: Wrote 0x258h to  EPWM_TBPRD 

                => mw.w 0x2301000A 0x258

    step 5: Wrote 0x0c to CMPB Register

                 => mw.w 0x23010012 0xc8

    step 6: wrote 0x12 to EPWM_AQCTLA Register

                 => mw.w 0x23010016 0x0012

    Can you please check and let me know, where i am going Wrong.

    Thanks,

    Murali C

  • 0 in reply to Murali Chikkanna
    TI__Guru** 101260 points

    Hello Murali,

    As Hong indicated, this is not a usecase that we have specifically enabled in software.

    After enabling the clocks to the PWM, you can try reading from the PWM memory space. If you are able to perform valid reads, I would expect that means that the peripheral is being properly clocked.

    In terms of the actual steps to configure the PWM by directly writing to the registers, the technical reference manual (TRM) is your best resource. If you need additional code references and the Linux driver is too complex, you might be able to reference the RTOS EPWM drivers of a similar device. e.g., AM64x MCU+ SDK, under source/drivers/epwm.

    Regards,

    Nick

  • 0 in reply to Nick Saulnier
    Prodigy 145 points

    Hi Nick,

    Thanks for the reply.

    i will try to read the PWM memory space.

    Regards,

    Murali