Need help on configuring port 2.6 as input(MSP430G2231

HI,

It is not clear from your post quite how your switch is connected. It could be connected to Vcc or 0V. You also do not mention if you have a pull-up or pull-down external resistor.

Assuming you have no external resistor you need to enable the internal resistor.

For switch connected to Vcc you need.

P2DIR &= ~BIT6;   // Set port to input

P2OUT &= ~BIT6;  // Set up for Pull down resistor

P2REN |= BIT6; // Enable internal resisor

For switch connected to Vcc you need.

P2DIR &= ~BIT6;   // Set port to input

P2OUT |= BIT6;  // Set up for Pull Up resistor

P2REN |= BIT6; // Enable internal resisor

Then enter your while loop

Regards

 Roy

Hi Roy

Thank you for your reply. The code you have posted is help-full. There has been an improvement in my results. After pasting your code for 'Set up for Pull down resistor' I am no longer getting a 1.5V at 2.6 when the switch is off. However my code is detecting a high always, i.e G_Charge_Start is always 1, inspite of turning off the switch. I have also attached my switching circuit along with this post. In the diagram when P+ is high(when external switch is turned on) panel detect presents 3.3V to Port2.6. Else no voltage present at panel detect. My code now looks like the one pasted. And also find attached the switching CKT 

int main(void) {
WDTCTL = WDTPW | WDTHOLD; // Stop watchdog timer
// INIT_PORTS();
P2DIR &= ~BIT6; // Set port to input

P2OUT &= ~BIT6; // Set up for Pull down resistor

P2REN |= BIT6; // Enable internal resisor
while (1)
{
// battery_voltage = analogRead(port1);
if (P2IN & BIT6) {
G_Charge_Start=1;
} else if( !(P2IN & BIT6)) {
G_Charge_Start=0; // ... else turn it off.
}

}
}

Hi,

Currently you have

:

Rx is the pull down resistor, and Vx is the actual voltage at the pin. Hence there is a potential divider between R18 + on resistance of OPTO, and Rx. Rx you can find from the datasheet for the processor but the effective resistance of the Opto is more difficult to calculate for certain.

Can you change your circuit to:

With this revision, when the Opto is off the port pin is pulled directly to 3.3 via R18. With the opto ON the port pin should be pulled down to the Vce saturation voltage of the Opto transistor.

Also you can make you while loop:

while (1) {
  // battery_voltage = analogRead(port1);
  if (P2IN & BIT6) {
    G_Charge_Start=1;
  } 
  else {
    G_Charge_Start=0; // ... else turn it off.
  }
}

The current "else if" clause is redundant.

Hi 

Thank you for the reply.

I have tried ur suggestion. The problem is that the microcontroller is always detecting a high(G_Charge_Start=1) irrespective of the voltage given to the microcontroller, i.e what i'm saying is irrespective of 3.3V or 0V given to the microcontroller. it is always detecting a high. Please can you tell me the reason for this.

Hi,

Looking at the port schematic in the datasheet on P44. It would appear that the input pin is fed to a Schmitt Trigger that contains an enable.this appears to be to allow the pin to operate in oscillator mode.

To ensure that this mode is disabled you can try to add

P2SEL & =~BIT6 

to ensure the oscillator function is disabled. Usually from a restart this bit is clear and you have to explicitly enable it to get the oscillator to work.

Other than this the value from P2IN bit 6 should reflect the voltage on the pin so if this is not your problem, I am out of ideas.

Roy

Roy Deabill said:

Looking at the port schematic in the datasheet on P44. It would appear that the input pin is fed to a Schmitt Trigger that contains an enable.this appears to be to allow the pin to operate in oscillator mode

Your close, but you need to switch off the VLO: BCSCTL3 = LFXT1S_2;

Leo Bosch said:

you need to switch off the VLO: BCSCTL3 = LFXT1S_2;

To be clear, "BCSCTL3 = LFXT1S_2" sets the LFXT clock source to use the VLO, disabling the crystal oscillator.

The crystal oscillator pins XIN and XOUT are multiplexed with P2.6 and P2.7 on the MSP430G2231, so you need to disable the oscillator if you want to use those pins for IO.

Robert Cowsill said:

you need to switch off the VLO: BCSCTL3 = LFXT1S_2;

To be clear,

[/quote]

Thanks, I was close but wrong tekst.

The diagnostics are right but the cure is wrong.

Jens-Michael Gross said:

The diagnostics are right but the cure is wrong.

Looking into the users guide reveals that P2SEL has a default value of 0xc0. Which selects P2.6 and P2.7 for XT1.
To use these pins for GPIO, P2SEL needs to be cleared.
P2SEL&=~(BIT6|BIT7); or simply P2SEL=0;

This I’m not fully agreeing with you. ‘LF off’ is overruling the P2SEL state as long this is on, the port pins are not freed from Xtal whatever state P2SEL has. Both needs to be altered.

Checking the port pin schematics once more, LF off controls the oscillation inverter between 2.6 and 2.7, along with P2SEL (so both must fit to have the inverter on), but for activating or deactivating the digital port pins, only P2SEL is important. So clearing P2SEL deactivates the inverter and activates the digital I/O, independently of LF off. Which of course can be set too, to remove the oscillator fault condition on LFXT1. But for GPIO operation of the port pins, it is unimportant.