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  • Author Author: Jan Cumps
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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 330 Ohm 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

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