help with pcb

Hello all,
i made bose controller to use with my docing station. Everything works perfect on breadboard (connection below 1st pin is +5V, 2nd is GND, 3rd is Rx, 4th is Tx) - attach 1 (ss.jpg) . Then i created pcb to put all elements on it and unfortunately it doesn’t work - attach 2 (ss2.jpg). There is only diode lit but no communication to microcontroller. I assume that is something wrong with pcb. Could someone take a look and help ?

Thanks,
pater

ss.JPG

where is the picture of the pcb design?

The CAP/Crystal wiring in the breadboard picture is pretty significantly wrong; everything is shorted to GND. If fritzing was used to make a PCB based on that picture, it may be wrong too...

i made mistake in breadboard correct one i put in attachment and pcb as well

One thing I spotted is that you have no power supply decoupling, nor is there a capacitor on the Vref pin.

Also it looks like you have the chip back to front, that would be alright if the tracks were on the top and you were soldering the chip to them. However, if we are looking at the tracks from the underside and the chip is inserted from the other side of the board then pin 1 is not in the right place.

the pcb is mirrored view ready to transform to pcb so pins are correct. Could You explain me deeply about power supply decoupling ? What pin should have capacitor ( regarding to datasheet there are 3 pins which needs to be supplied with power ). I am beginner so it is like black magick for me :slight_smile:

thanks a lot,
pater

See http://www.thebox.myzen.co.uk/Tutorial/De-coupling.html You need caps on each of the power lines and the Aref pin

ok i will add caps to pcb, but as i understand right, it can cause random erratic behaviour, so the same situation sould be with breadboard, but it wasn't :/.

It depends on how you powered the bread board and what testing you did under what conditions. It is like saying I drove my car yesterday and sent a text message at the same time and nothing happened to me so it is always safe to do that.

so the same situation sould be with breadboard, but it wasn't

Those breadboards have a lot of intrinsic capacitance that can sometimes hide this sort of thing.


Rob