11 years, 9 months ago.

NXP LPC11U24 not starting up from VB power when sleep() is included

I'm having difficulty getting the mbed, NXP LPC11U24, to start up using only VB power when sleep() or deepsleep() is included in the code. The board has two different power pins, VB and Vin. Vin powering the entire board, while VB only powers part of it. My project requires power conservation so it would be ideal to only power the board using VB and to allow the program to sleep whenever it is not actively in use.

The issue I'm having is that when my code includes a sleep sate, the mbed will not work when powered from VB unless it is temporarily powered by Vin. The code will have already been loaded from USB and run once through USB power and work fine. When it is only powered from VB, however, the code will not run. The mbed will not do anything. If Vin is briefly powered, for a second or two, the program will run correctly with only VB power from then on out. This issue disappears completely when sleep is removed. The board will start up and function properly from just VB when sleep is commented out.

Here is a sample of my test code bellow. As is, the code requires Vin to briefly power the board before it can run with just VB. If "sleep();" is comment out, the issue disappears. This makes me believe there is something in sleep() and deepsleep() that is causing the issue, however, I cannot find it. Can anyone come up with a fix that allows for sleep to be included and not run into this issue?

#include "mbed.h"

// The code is designed to turn LED1 on for a second when a button is pushed that is connected to pin 5.  The code is meant to sleep while the button is not pressed
// and awake and blink once when the button is pressed before falling back to sleep.

void check_bounce();    // Simple function to test if the button is actually pressed or if it is simply a bounce.
void blink();   // Function that turns LED1 on for a second before turning it off.
bool enable;    // Value to prevent an inturrupt from activating blink() if blink() is already running.
InterruptIn button(p5);     // Declares the button at pin 5 as an interrupt.
DigitalIn button_poll(p5);  // Declares the button avaliable for polling as well.
DigitalOut myled(LED1);     // Declaration for LED1;

int main()
{
    button.rise(&check_bounce);
    while(1)
    {
        enable = 1;
        sleep();
    }
}

void check_bounce() // Ensure the button is not bouncing by waiting to see if 10 ms later the button is still pressed.
{
    wait_ms(10);
    if(enable && button_poll.read())
    {
        enable = 0;
        blink();
    }
}


void blink()
{
    myled = 1;
    wait(1);
    myled = 0;
    wait(1);
}