CCS/TMS320F28388D: One shot

Bob Snyder1

Part Number: TMS320F28388D

Tool/software: Code Composer Studio

I need to generate a 30us (one shot) pulse that is triggered by software. I know I can do this with timers/interrupts, but I'm sure there must be a more elegant way using the PWM for instance.

Can someone please point me in the right direction?

Bob

over 5 years ago

0 Subrahmanya over 5 years ago

TI__Mastermind 24095 points

Hi,

Yes - you can do this via software as you mentioned.

You could use PWM as well, but PWM doesn't have a single pulse generation capability. But you can switch the configuration dynamically (software intervention needed).
For ex: You can set the Period and action qualifier setting to generate a pulse of your interest as Config-1. Then have another config-2 to do nothing. You can dynamically switch between these configurations in software as needed. Refer to "26.6.4 AQCTLA and AQCTLB Shadow Mode Operations" of the TRM.

You could also use CLB (configurable logic block) to create this function.
Refer to http://www.ti.com/microcontrollers/c2000-real-time-control-mcus/overview.html#clb

0 Bob Snyder1 over 5 years ago in reply to Subrahmanya

Intellectual 370 points

I ultimately used something like example 6 (monoshot) as a starting point. Rather than use the second PWM as my control I have an external pin (which I use to signal the start of my timing loop) to trigger my one-shot. It works fine but I'd rather not have my 30us one shot triggered by hardware.

Should I get more serious about looking at section 26.6.4?

0 Subrahmanya over 5 years ago in reply to Bob Snyder1

TI__Mastermind 24095 points

Hi,

What would you prefer to be the trigger for your monoshot pulse?

0 Bob Snyder1 over 5 years ago in reply to Subrahmanya

Intellectual 370 points

As a test, it took the example program (EX6 i believe), and instead of using the second PWM as a trigger for the one shot/monoshot thru the XBAR connection I took one of my GPIO's (what I use as an oscilloscope trigger), 'routed it' to the XBAR connection so that it triggers the one shot.

What I would prefer is to have a simple function called 'start one shot' that triggers the one shot with out having to toggle a pin to do so.

Bob

0 Subrahmanya over 5 years ago in reply to Bob Snyder1

TI__Mastermind 24095 points

Hi,

In this test ePWM1 is used to generate the monoshot output and ePWM2 is used an external trigger for that. No external connections are required as ePWM2A is fed as the trigger using Input X-BAR automatically.

You can choose to not use ePWM2. configure the pin ( GPIO 2) as GPIO instead of PWM2A and create your own software function that writes to the GPIO2 as trigger.

0 Bob Snyder1 over 5 years ago in reply to Subrahmanya

Intellectual 370 points

Agreed, that is basically what I did, just with a different GPIO pin. I was just thinking perhaps there would be a way to do this without using a GPIO pin. If not, I'll just move forward with what I have.

0 Subrahmanya over 5 years ago in reply to Bob Snyder1

TI__Mastermind 24095 points

Hi,
Since you are using GPIO (EPWM2) as Sync input to trigger EPWM1,
You can simple force a sync pulse by writing to TBCTL[SWFSYNC] in EPWM1 register space.

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CCS/TMS320F28388D: One shot