Atmega328pb - cannot get any LED's to turn on!?

albertsm · Joined: 09 Apr 2004 Posts: 5915 Location: Holland

with an ohm meter measure all GND and VCC/AVCC pins (with power off) and see if they are all actually connected !
this means : are all GND pins actually connected to ground.
are all vcc and avcc pins connected to your vcc power?

then check in volt mode again with power applied and see if the levels are ok.

also : which casing are you using? Does it match the datasheet/cad circuit?
some casing have different pinning.

Printpix52 · Joined: 18 Jun 2014 Posts: 282 Location: D.F.

I think the problem is the LED resistor replaced by 82 ohms. Very Happy

Printpix52 · Joined: 18 Jun 2014 Posts: 282 Location: D.F.

To calculate resistances......

https://www.inventable.eu/paginas/LedResCalculatorSp/LedResCalculatorSp.html

SZTRAD · Joined: 30 Dec 2019 Posts: 165

I would be very careful with that.
I recommend reading the electrical characteristics in the data sheet.

hgrueneis · Joined: 04 Apr 2009 Posts: 902 Location: A-4786 Brunnenthal

You loaded the chip with the leds without connecting all power pins.
I suspect that one or more internal power lines are blown, maybe also the output buffers.
I would try an other chip.

Regards
Hubert

hgrueneis · Joined: 04 Apr 2009 Posts: 902 Location: A-4786 Brunnenthal

I do not think that an 82 ohm resistor would be the problem, since most leds require 1.5 to 3 volts to light up.

Regards
Hubert

SZTRAD · Joined: 30 Dec 2019 Posts: 165

This is the standard approach of the programmer and not the person who does the HW.
I did not draw attention to the voltage but to the current. These 4 LEDs almost reach the limit of the chip used.
The disappointment is then terribly great when the chip is smoked. Forget the many connections with arduino and read the data sheets. If nothing else, at least the supply voltage and maximum current. Sometimes try to measure the short circuit current of the port and you will understand.

enniom · Joined: 20 Oct 2009 Posts: 537

Tim,

One last guess ...

From the symptoms you describe, it may be possible that the PUD is set.

From the datasheet:

PRINT out the value of MCUCR.PUD to see if it equals 0.

Also note that unlike the Mega328P, the Mega328PB has a JTAG interface with a corresponding fuse bit. Make sure that it is disabled. It is not clear from the datasheet which pins are affected, but its possible that the JTAG overlays on the SPI pins.

If the JTAG is set, bit 7 of the MCUCR register should be 1.

E

TSEYFARTH · Joined: 01 Jul 2006 Posts: 1054

Found the problem!

It was running too fast - 16MHz. The max on 3.3v is 10MHz. Using divide by 8 fuse and quick change to the code corrected the problem.

Thought I'd let everyone know...

Thank you for all of the suggestions and help!
Tim