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

TSEYFARTH · Joined: 01 Jul 2006 Posts: 1054

Hello all.

I have a simple program and all I want to do is to turn on a couple of LED's using the Atmega328PB. Even when I use the sample program and add the code they still wont turn on.

TSEYFARTH · Joined: 01 Jul 2006 Posts: 1054

I've also tried with an ATMEGA88 - which is pin compatible, at least for the pins I am using!

Still no good.

If I bypass the uC and bring ground to the LED, it does turn on, but will not turn on with the uC.

Any help/ideas would be appreciated!
Thank you,
Tim

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

Positive anode and negative cathode turn on led and positive anode and positive cathode off led.

enniom · Joined: 20 Oct 2009 Posts: 537

EDC · Joined: 26 Mar 2014 Posts: 971

Why not to ground pin 21 on the schematic? Very Happy

Your code copied from this forum is working -> see pics.

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

avcc seems unconnected.

when searching for problems :
- check short circuit between gnd and vcc but since the firmware programs that should be no problem
- check short circuit on the output pin
- check voltage. simple way is to to use 2 led with one led reverse connected. and of course with a series resistor

then it is important that the good way to connect is as you did between vcc and the port : making a port pin low will make the led light
of course new avr also allow to connect between the port pin and gnd : making a port pin high will make the led light

the total mA a port/processor can draw you can find in the datasheet.

since that is all ok i assume that avcc is the problem.
you can also do the simple test :

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

SZTRAD · Joined: 30 Dec 2019 Posts: 165

Unfortunately I don't have AT328PB connected here, but all other atmegs have internally connected GND.
I'm not saying they shouldn't get involved.
A fellow interviewer did not write if the transfer to COM works for him. If not, his chip isn't working. If so, RESET is active (externally or internally).

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

A 10K pullup on the RESET might also be helpful.
Regards
Hubert

MWS · Joined: 22 Aug 2009 Posts: 2262

And don't use blue or white Leds with a VCC of 3.3V ;D

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

If you doubt all the help , that very experienced people give you here, then you should go somewhere else.
You do not even attend to the bare essentials of the electronic requirement for these processors.
My advice, study the datasheets and the Bascom Help. When you are through with that and you still have problems, come back here.
Otherwise "Good luck"

Regards
Hubert

TSEYFARTH · Joined: 01 Jul 2006 Posts: 1054

Hello all and THANK YOU for all of your helpful responses!

I'm trying the suggestions and will get back with you all.

Thank you again,
Tim

Duval JP · Joined: 22 Jun 2004 Posts: 1161 Location: France

a scope is a a good friend Wink

jp

TSEYFARTH · Joined: 01 Jul 2006 Posts: 1054

Checked with a scope and meter. The pins at the uC stay at 1.7 Volts. They never go to a true hi (3.3) or low.

Other than what has been suggested already, anything else to look at?

Thanks all!
Tim

TSEYFARTH · Joined: 01 Jul 2006 Posts: 1054

Also tried toggling a spare set of pins that are not connected to anything. According to the scope, they stayed low and never changed.

Must be something with the PCB or chip? It programs fine so the xtal should be OK, all of the power and grounds are set up now.It is getting 3.3V.

I've never had a situation where the chip did not respond properly.

Any ideas?
Tim