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Have 5V supply to ATmega32 but no voltage across pin 1??

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kris_maher

New Member
Hi guys,

I'm working on a project which is based around ultrasonic transducers.

I have a 9V battery which I was able to get down to 5V thanks to a voltage regulator whose wire is connected to the VCC pin (10) on my chip.

All the GND are grounded on the breadboard, pins 11 and 31 are connected firmly to ground

I checked with Multimeter and there's 5V across VCC as expected, and there's 5V across the RESET pin (pin 9) as expected and 2.5V each for XTAL2/XTAL1 (pins 12 and 13. These are related to the connection of external inverting amp etc).

I'm using an internal timer. My dilemma is that I've created a timer signal that oscillates at 100Hz sent to PORTB bit 0 (Pin 1). I have a buzzer connected to it along with the other wire of it to GND.

The buzzer beeps as expected on the development board but when I put the chip over to the breadboard when I check the voltages there's no voltage signal at all on pin 1 - it's only at 250mv and I need 3.3V min across pin 1 to drive the buzzer. When the ATmega32 chip is on the development board, there is a constant 3-4V across pin 1.

Even something as simple as an LED does not flash when the chip is on the breadboard and wires all connected, even though it does on the development board when connected to pin 1 and the other leg to ground.

Any ideas on why there's no voltage reaching pin 1 guys?

Thanks

PS: All wires are firmly connected and I checked several times against the datasheet's pin configuration diagram.
 
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eblc1388

Active Member
Any ideas on why there's no voltage reaching pin 1 guys?.
You AVR is not running.

What kind of clock source are you using when the M32 is on the breadboard? On the development board you probably was using ext. crystal oscillator. Do you have a crystal on the breadboard?

Are you using internal or external oscillator?

Can you post a schematic?
 

kris_maher

New Member
I'm using an internal oscillator.

I've taken screenshots of my current configuration:
http://allnite.files.wordpress.com/2009/04/breadboard.jpg
http://allnite.files.wordpress.com/2009/04/bb_closeup.jpg

In terms of a schematic I don't have much of a schematic since it's basically the ATmega32 chip, a voltage regulator circuit supplying a constant +5V to VCC and AVCC and all the other standard GND connections (pin 11 and 31). The other wires on the picture are interconnects to supply power throughout the board.

I don't think I touched the clock fuses? perhaps it's still on 1MHz? I've never touched the clock fuses before and I'm not sure how to do that. My code is written to run at 8MHz. Do I change the clock fuses in avrdude (that's what im using to program the chip)?
 

Sceadwian

Banned
Umm.. Did you notice that you left your reset pin floating?
Tie it to VCC and put a .1u cap between it and GND. Proper decoupling for the reset line is a must, especially on breadboard with all that parasitic capacitance. Your chip is probably being held in reset.
 
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Sceadwian

Banned
I doubt it was the fuse, if you leave that reset line floating like it's like flipping a coin weather or not the chip will power on or reset randomly.
 

Sceadwian

Banned
hmm, guess I missed that, though most people use a lower value resistor, the built in one isn't so great for noise immunity.
Odd that it would start up on the dev board but not the bread board before you changed the fuse though, unless your dev board was really supplying the clock.
 
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