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Hi again !

I'm using a nano 18 on one of my projects and i ran into a pretty bizzare problem, as its not the first time i make PCB's myself to support a nano 18 but this time the chip seems very unstable. I added blinking led commands to try and visualise if the code reads well since the circuit didn't work properly in the first place, and what i see is very ugly. The chip seems to run arkwardly, making skips in the code, (or resetting, as its a pretty simple loop, can't really tell with just one led) and sometimes stopping, then iddling and restarting. I cheked the supply line and it seems alright, with a steady 4.9 volts from a LM7805C, as well as the RES. The chip ain't broken either, as i cheked it on a dev board and it runs fine.

Now the only thing i didnt checked right now is the current going into the chip, as it would require pretty tedious unsoldering, so I ask here first in case anyone has super duper nice ideas on what my problem may be.

also, if someone could make a kind of like ''Ideal wiring diagram'' for a stand alone nano 18 i would appreciate, since i'm never sure of doing everything right. I know i need to pull up the RES with a 10k and connect VCC and VSS on the ground and output pins of a regulator but is it anything that i'm missing ?

thanks !

It sounds like something is going on with your incoming power if it runs fine in the dev board. I just assembled my standalone circuit yesterday and it's running like a champ. Since I needed to power my circuit from 120VAC, I used a Cosel VAA5 PS. RES is tied to 5V through a 10k just as it states in the data sheet. There really isn't a lot to it. Have you put a scope on your incoming 5V supply? A DMM doesn't give enough information.

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Studio 2.0.0.16 on Win 7 Home x64 updated daily - Original Roboclaw 5A V1.3.9
Mostly a Nano40 for prototyping, but I have others in my bins

Is your project board setup to allow programming the Nano on it? Also providing your code could give an answer. A return without a gosub or a gosub without a return can cause seemingly random resets/problems.

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Basic Micro - Robotic Technology Evolved

I don't program it directly on my homemade, i use a chip holder and transfer the chip everytime, its a bit safer as for the code its very very simple and runs fine on the dev board.

i looked however at the current going into the chip and its something like 11-12 milliamps, if i'm not mistaken the nano is supposed to draw 50 milliamp iddle so i'm prerty sure my problem comes from there. Altough i really don't know what could limit the current that much, as my 5 volt comes from a regulator drawing from a 9 volts battery. Anyway thanks for the answers, ill continue looking into this and give some feedback, if you think of anything else let me know

No, the nano wont draw 50ma unless you are running leds on the I/Os or something. 11 to 12 is about right if you are using a voltage regulator.

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Basic Micro - Robotic Technology Evolved

Sorry i made a mistake in my readings for the previous post ; the values i gave are 10 times bigger than the real ones so its about 1.2 ma going in the chip.

We have had the occasional post where the problem proved to be a low 9V battery feeding the 5V regulator. The 9V was actually 6V or less. The regulator drops 2V or more internally on its own (well, the cheap-o, plain vanilla ones), so you get less than 5V out of the regulator. Check your Vcc voltage as you exercise the board and see if it stays close to 5V.

Be sure you have the necessary capacitors at the regulator and have a bypass cap at the Nano itself.
As for the "ideal wiring diagram", just use the data sheet's schematic for the dev board as a guide.
Take care.
kenjj

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kenjj
http://blog.basicmicro.com/
http://kjennejohn.wordpress.com/

I assumed you were using a linear voltage regulator or had leds ont he nano. The nano itself will usually only pull around 1 ma. A linear voltage reg can pull extra power because its disipating power to lower the voltage to the regulated level. ALso any load on the nano I/Os will pull more power.

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Basic Micro - Robotic Technology Evolved

Maybe you should just post a picture of your board. We may be able to see a mistake that way.

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Basic Micro - Robotic Technology Evolved