Group Actions
Engagement
  • Author Author: Jan Cumps
  • Date Created: Date Created
  • Views 56 views
  • Likes 6 likes
  • Comments 5 comments
Related
Recommended

switch up to 5V and 8 mA with MSPM0 Open Drain IO

Jan Cumps

The Texas Instruments MSPM0 microcontroller has a few open drain GPIOs. TI calls them ODIO. These are 5V tolerant, and can switch up to ( see   comment below) +-8 mA. The main purpose is to support multi-level IO. 
They can do general low side switching too. That's what I'm checking out in this post. I use a ODIO to blinky an LED.

image
image: EasyL1105 controling an LED with open drain IO

The standard GPIOs can source 3.3V, 6 mA (with caveats). Can be used to modestly blink efficient LEDs. But if you want to control a small LCD's backlight, this 5V, 8 mA capability can save a few components.

From TI's documentation:

image

"... the open drain IO only implement a low-side NMOS driver and no high-side PMOS driver. The 5V-tolerant
open drain IO are fail-safe and may have a voltage present even if VDD is not supplied"

"ODIO can be used to implement communication with a 5V device."

image
source: MSPM0 L-Series MCUs Hardware Development Guide and MSPM0L110x Mixed-Signal Microcontrollers datasheet

What does this project do?

It's the blinky. TI calls it gpio_toggle_output. It blinks an LED every second. The only change I made, is to define open drain pin PA0 as the LED pin. The code is just a simple loop that toggles the pin, then delays half a second.

But what it actually allows you to do, is test that the MSPM0 ODIOs are capable to switch a 5V powered load.

Hardware resources

LED1 PA0 Led with 330R resistor in series
Powered by 5V

The circuit is simple. A red LED with a 330V resistor in series. When PA0's gate is driven high, the current in this circuit, and through PA0's channel, will be around 10  7 mA.

I used the 5V of my EasyL1105 kit. If you use a LaunchPad: they have a 5V supply too.

image

Testing

Program the MSPM0LL05 with the attached CCS project code. If you have a debugger, you can do this from CCS. I've also provided a .hex firmware that can be used with  ' bootloader utility.

Code highlights

In SysConfig, PA0 is set up as an open drain output.:

image

The code is extremely simple:

/* This results in approximately 0.5s of delay assuming 32MHz CPU_CLK */
#define DELAY (16000000)

int main(void)
{
    SYSCFG_DL_init();

    while (1) {
        delay_cycles(DELAY);
        DL_GPIO_togglePins(GPIO_GRP_ODIO_PORT,
            GPIO_GRP_ODIO_PIN_ODIO_0_PIN);
    }
}

What's next? PA0 can be driven from a PWM peripheral. That allows you to dim a small LCD's backlight without external transistors.

Have fun!

ccs project adapted to EasyL1105 (with bootloader compatible .hex firmware): EasyL1105_odio_sink_20251118.zip

Related posts

Parents

  • That's very neat! Awesome that the microcontroller has this feature. Since it also follows that the input for those pins must be 5V tolerant too, then it would be easy to use the microcontroller to interface with legacy 5V protocols like 1-wire and so on, with no extra components either. And the ability to directly drive MOSFETs (for at least some use-cases) with the higher 5V rather than 3.3V is also extremely useful. 

    image

Comment

  • That's very neat! Awesome that the microcontroller has this feature. Since it also follows that the input for those pins must be 5V tolerant too, then it would be easy to use the microcontroller to interface with legacy 5V protocols like 1-wire and so on, with no extra components either. And the ability to directly drive MOSFETs (for at least some use-cases) with the higher 5V rather than 3.3V is also extremely useful. 

    image

Children
No Data