PortB0 stuck at 2.5V

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npat_avr
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Posted by npat_avr: Wed. Dec 9, 2009 - 12:31 PM
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Hi Freaks,

I am using a M328P and am using PORTB pins as output pins.

My code to set PORTB as output is very simple:

	   DDRC = 0x0F;
	   DDRD = 0xC0; 
	   DDRB = 0xFF;
	   PORTC = 0x00;
	   PORTD = 0x00;
	   PORTB = 0x01;

I am making PORTB0 high.

However when I measure the voltage on the PORTB0 when I turn on the power, I get 2.5V (about half of supply voltage).

All the other PORTB channels are working fine.

What could be the problem? Did I fry the chip?

Thanks.

Tags:

AVR Microcontrollers, megaAVR and tinyAVR
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ossi
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Posted by ossi: Wed. Dec 9, 2009 - 12:35 PM
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Perhaps the pin is connected to another pin.
One pin drives high, the other low, result
about 2.5V. So check the other pins

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DrWhom
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Posted by DrWhom: Wed. Dec 9, 2009 - 03:21 PM
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I had a similar issue when I tried to access a port that was setup as an input. I needed to make PINB = 0x00. PINB for input, PORTB for outputs. This is probably not your problem as mine was a noob mistake

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sbennett
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Posted by sbennett: Wed. Dec 9, 2009 - 08:24 PM
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CKOUT Fuse programmed?

Quote:
ICP1/CLKO/PCINT0 – Port B, Bit 0

CLKO, Divided System Clock: The divided system clock can be output on the PB0 pin.
The divided system clock will be output if the CKOUT Fuse is programmed, regardless
of the PORTB0 and DDB0 settings. It will also be output during reset.

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npat_avr
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Posted by npat_avr: Thu. Dec 10, 2009 - 10:23 AM
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That did it,sbennet. Wow, I would never have stumbled upon it. I guess reading the datasheet helps. Thanks.

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joeyAVR
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Posted by joeyAVR: Thu. Dec 10, 2009 - 03:50 PM
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That was my guess - 2.5V is 50/50 duty cycle :)

Cheers,

Joey

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