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OMAP-3730 kernel development

rajalakshmi A
Prodigy 20 points

Other Parts Discussed in Thread: TPS65950

Hi

I am using tdm3730 module for my project .. I need omap-dmtimer documentation  for my study purpose.

In Omap 3730 , I want  to implement variable dutycycle from 0 to 100%  for  10ms  in pwm kernel driver.. Any one help me to finish it off.. 

  • 0
    TI__Guru**** 393215 points
    Moving this to the DM37X forum.
  • 0
    TI__Guru 65405 points
    Hi Rajalakshmi,

    The integrated power management module is responsible for the pwm. Therefore you need to send a command to the power management circuit of your board to start sending PWM signal with desired duty cycle. There is an example which makes this with TWL4030 power management circuit:
    /*
    * PWMA/B register offsets (TWL4030_MODULE_PWMA)
    */
    #define TWL_LED_EN 0x0
    #define TWL_LED_PWMON 0x0
    #define TWL_LED_PWMOFF 0x1

    static void omap3evm_set_bl_intensity(int intensity)
    {
    unsigned char c;

    if (intensity > 100)
    return;
    /*
    * Enable LEDA for backlight
    */
    twl_i2c_write_u8(TWL4030_MODULE_LED, 0x11, TWL_LED_EN);

    if (get_omap3_evm_rev() >= OMAP3EVM_BOARD_GEN_2) {
    c = ((125 * (100 - intensity)) / 100) + 1;
    twl_i2c_write_u8(TWL4030_MODULE_PWMA, 0x7F,
    TWL_LED_PWMOFF);
    twl_i2c_write_u8(TWL4030_MODULE_PWMA, c,
    TWL_LED_PWMON);
    } else {
    c = ((125 * (100 - intensity)) / 100) + 2;
    twl_i2c_write_u8(TWL4030_MODULE_PWMA, 0x1,
    TWL_LED_PWMON);
    twl_i2c_write_u8(TWL4030_MODULE_PWMA, c,
    TWL_LED_PWMOFF);
    }
    }

    from kernel/arch/arm/mach-omap2/board-omap3evm.c file.

    BR
    Tsvetolin Shulev
  • 0 in reply to Cvetolin Shulev-XID
    Prodigy 20 points
    Hi Shulev ,
    Thanks for your mail. But i want to vary the period and frequent dutycycle variation like 5%, 10% ,25% to generate spwm .Will you help me how to write kernel code or user space code.
    I tried with With this below pwm driver but i cant see any dutycycle variation in scope.
    sweet.io/.../omap3-pwm
  • 0 in reply to rajalakshmi A
    TI__Guru 65405 points
    Rajalakshmi,

    If you wish to check the PWM parameters (duty cycle and frequency) with software method you should read the corresponding register of the power management circuit using the int twl_i2c_read_u8(module, &check, address) function.
    I suggest you to read section 8.4 LED Driver and PWM Generators Functional Description from the TPS65950 OMAP(TM) Power Management and System Companion Device ES 1.2 TRM guide at:
    www.ti.com/.../technicaldocuments
    for understanding the PWM mechanism.

    BR
    Tsvetolin Shulev