LPC1768 Problem: High pin suddenly goes to zero when the state of another pin changes

[contr2889]

Hi everyone,

    I have a problem with lpc1768. I have configured 2 pins (p0.24 and p0.25) as open drain with external pullups of 10k to 3.3V. The problem is, when I have p0.24 and p0.25 in high state and then set the value of p0.24 to low state, the other pin briefly change the state to low level and then go back to high state, as you can see in the attached image. p0.25 should not be split in two pulses.

 

here is my test code:

void Sensor::init()
{
    //para pines p0.24 y p0.25
    LPC_PINCON->PINSEL1 &= 0xFFF0FFFF;
    LPC_GPIO0->FIODIR |= 0x03000000;
    LPC_PINCON->PINMODE1 |= 0x000A0000;  
    LPC_PINCON->PINMODE1 &= 0xFFFAFFFF;
    LPC_PINCON->PINMODE_OD0 |= 0x03000000;
    LPC_GPIO0->FIOMASK3 &= 0xFC;
}
void Sensor::measure(void)
{
    sdaSCLSet(1,0);
    wait_us(50);
    sdaSCLSet(1,1);
    wait_us(50);
    sdaSCLSet(0,1);
    wait_us(50);
    sdaSCLSet(0,0);
}
void Sensor::sdaSCLSet(uint8_t sdaValue, uint8_t sclValue)
{
    uint8_t outputPins = LPC_GPIO0->FIOPIN3;
    sdaValue > 0 ? outputPins |= 0x01 : outputPins &= 0xFE;
    sclValue > 0 ? outputPins |= 0x02 : outputPins &= 0xFD;
    LPC_GPIO0->FIOPIN3 = outputPins;
}

and the code in main is:

sensor.init();

wait(1);

sensor.measure();

If p0.25 start in high level and then change p0.24 to high level  and then change p0.25 to low level then p024 stays in high level as should be, there is not the problem depicted before.

What could be the problem? 

Thanks for your help.

[xiangjun_rong]

Hi,

It appears that your code has issue.

Anyway, pls try to modify the code like.

Hope it can help you

BR

XiangJun Rong

void Sensor::measure(void)
{
    wait_us(50); //Rong wrote
    sdaSCLSet(1,0);
    wait_us(50);
    sdaSCLSet(1,1);
    wait_us(50);
    sdaSCLSet(0,1);
    wait_us(50);
    sdaSCLSet(0,0);
}