TMS320F28335: PWM module driver startup process

Seven Han

Hi，

When I debugged the device, I found that the PWM port output level is not controllable during the DSP start-up. As the oscilloscope diagram shows, the PWM level during startup is 1.9V. can you tell me why and How to solve it? thank you very much！

GPIO0(EPWM1A)

GPIO1(EPWM1B)

GPIO2(EPWM2A)

GPIO3(EPWM2B)

over 8 years ago

0 Gautam Iyer over 8 years ago

Guru 192875 points

Hi Seven,

Does the design have an external pull-down? If not, its very much recommended. Use a 10k resistor to pulldown the pwm pins.

Regards,
Gautam

0 Seven Han over 8 years ago in reply to Gautam Iyer

Intellectual 600 points

thank you Gautam，
Do you know what causes this phenomenon？
thank you again.

0 Cody Watkins over 8 years ago in reply to Seven Han

TI__Mastermind 42195 points

Seven,

during startup if VDDIO is brought up first the IO buffers will be in an unknown state, meaning they may drive the pin. During startup all pins are configured as inputs. GPIOs 0-4(other GPIOs may differ) will have their internal pull-up disabled by default, and thus will be floating.

My assumption is that something on your board is causing the GPIOs to float to 1.9V until the C2000 is configured to specifically drive them low. Assuming VDDIO doesn't lead VDD the C2000's IO buffer will not drive any GPIO pin(Note:The pull-up will still effect the Pin's value).

Regards,
Cody

0 Cody Watkins over 8 years ago in reply to Cody Watkins

TI__Mastermind 42195 points

Seven,
I am going to close this thread due to inactivity, if you are still having issues feel free to post them here on the forum.

Regards,
Cody

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TMS320F28335: PWM module driver startup process