Unexpected behavior of a simple design

As can be seen in the attached schematic i created a simple test rick involving a Arduino Nano and som simple input cricuitry.
Its quit simple but it doenst work. The power supply delivers the correct voltages.

The Nano simple connected to a USB cable works. For testing i uploaded the 1 sec blink sketch.

But when i place the Nano into the design the program doenst run. The blue led on top lights.
Even when the power is disconected nothing happens. I am out of suggestions. I checked every track on the PCB for a short but found none.
Its even stranger that as the design was firt build on a breadboard and that functions perfect.

Arduino_Nano_V031_sch.pdf (58.5 KB)

Where's the parts list? In particular what is IC6? Why is there a big black rectangle in the upper left of the diagram?

Pete

I designed a PCB that could have a NANO for development and after that a ATMEGA328 in the definityfe board.
But enclosed is the partslist. The only parts installed are the ones needed to use the NANO

DCC Turntable Controller V0.31_Parts.pdf (104 KB)

Even when the power is disconected nothing happens.

An odd thing to say, not many circuits start working when you remove the power.

The blue led on top lights.

Which is that one then?

But when i place the Nano into the design the program doenst run.

I bet it does, it probably doesn't do anything you can see.

Check the reset line is released. Modify the sketch to blink an LED in the start up routine so you can see the processor is running.

Then write small pieces of code that check out the individual hardware circuits. For example one to pulse the stepping motors, and nothing else. Another to look at the inputs and print the values to the console.

In particular what is IC6?

I looks like an opto coupled logic gate to me.

When the NANO is powered true the USB connection then it works.

The blue LED that lights is the one on top of the NANO.

As i installed the sketch to blink the LED on D13 to blink once per second i should see something.

One other thing is that when the NANO is placed in to the PCB, no power to the board, connecting the USB cable results in a message that the driver could not be installed. Thats even stranger. When the NANO is removed from the PCB and the USB cable is reconnected all is fine.

So what are you plugging into the serial interface connection on your board?

The serial interface is not installed. It is used only when the board is populated to use the ATMEGA328.
When the NANO is installed is will use the NANO USB interface.

connecting the USB cable results in a message that the driver could not be installed. Thats even stranger. When the NANO is removed from the PCB and the USB cable is reconnected all is fine.

Well that is your clue. I suspect it is not saying "the driver could not be installed" but the port could not be found.

You circuit board is stopping the Nano from working, you need to find out why.

First thing to check is the reset line, I can't see on the schematic where it is going, check it is not being held low. Then check that the RX and TX lines are not being held in one logic state by your board. Also check nothing is shorting or loading the 3V3 line. Next disconnect your 12V supply to the Nano and just let the USB power it.

Grumpy_Mike:
Well that is your clue.
I suspect it is not saying “the driver could not be installed” but the port could not be found.

Th eattached screen shot is in Dutch but it says that the USB device is not correct identified. I dont know the correct error message in Englisch.

First thing to check is the reset line, I can’t see on the schematic where it is going, check it is not being held low. Then check that the RX and TX lines are not being held in one logic state by your board.
Also check nothing is shorting or loading the 3V3 line.

As the resistors R2 and R3 are not installed and nothing is attached to it there’s way to put that line in a state.
The 3v3 line is not used in this design.

Next disconnect your 12V supply to the Nano and just let the USB power it.

No result

NoUsb.jpg

The problem is solved for now as i found the problem. I am using EAGLE to produce the schematics and PCB and the NANO library has a flaw in it.

In previos versions there was only one reset line but on the newer version there are two. By redesigning they made a mistake i dint see and no one here on the forum. Pins 28 and 29 are interchanged so the reset is on the ground level.

Found this out by soldering the NANO header pin by pin to the PCB and testing every step.

Found this out by soldering the NANO header pin by pin to the PCB and testing every step.

Well done.

But I did say:-

First thing to check is the reset line,