Hi all and thanks for reading.
I have been making my own PCBs using the ATMEGA328P-PU and Bootloading it either directly on the board or through a custom Bootloader that I made and they work great. I always load the Uno Bootloader.
I now want to start using the ATMEGA328P-AU as I have a SMD Rework Station and am confident in using it. Since though the AU version has more pins, I need to make sure I am wiring it up correctly. Also am going to have to Bootload them on the actual PCB that they are going to work on so need to make sure my Bootloading idea will work.
I currently Bootload my ‘PU’ versions using Arduino as an ISP as shown in attached image ‘Bootload PU.jpg’ and it works well. I then take the IC and put it in the PCB that it will be used in that has a TTL interface. I can then attach my FTDI unit to the interface and upload the code. The way I do it can be seen in image ‘ATMEGA328P-PU - Wire guide.png’.
I have looked at the differences between the ‘PU’ and ‘AU’ and have attached what I think is correct ‘compare.png’.
If I am correct, then I think that the ‘AU’ version should be wired like this ‘ATMEGA328P-AU - Wire guide.png’. Am I right?
I have then attached an image of what I think the differences are in a spreadsheet. Can somebody confirm that I am correct please.
Then I have some follow up questions:
The ‘AU’ has 2 extra pins 'ADC6' and 'ADC7', I read somewhere that these are extra analogue inputs, is this true? If so, would they then be A6 & A7?
Can I Bootload the ‘AU’ chip in the same way as the ‘PU’ chip using the attached wiring diagram?
I can still use the ‘Uno’ Bootloader on the ‘AU’ chip can’t I?
My wiring diagram for the ‘AU’ is it all ok or is it better to do it a different way?
I read somewhere that the caps between the GND and 5v need to be as close to the chip as possible. Is this correct?
On all my designs for the ‘PU’ I have not used caps between the GND and 5v, why are they required on the ‘AU’ version?
Is there any other useful information that I could do with knowing about the AU chip or general differences between the PU and AU?
Thanks all and sorry for so many questions.
This is how I bootload my 'PU' chips.
This is how I wire up my 'PU' chips.
This is how I think te 'AU' chip should be wired up
This is what I think the differences are between the 'AU' and 'PU'
The Atmega328pP AU is found on the Arduino Pro Mini which I have extensively used.
When you burn the bootloader select the board Arduino Pro Mini +5v.
If you are interested in proper design, always use ceramic .1uf capacitors on VCC to ground pins as close as you can get to the chip.
Also .1uf on AVCC and AREF to ground pins..
No you don't need the LED on Pin 13, I put it on there as it gives a nice blink to show that it is bootloading, but there is no need at all.
Why would you say to use ceramic capacitors over SMD? Since this is a SMD IC surely it would make more sense to have everything SMD just like on the genuine Nano and Pro Mini?
I have some 100nF which will use instead as they are equivalent to the .1uf you say to use.
So, is my wiring plan for the 'AU' correct? Should it Bootload and then actually run? Am I missing anything?
This is the actual Bootloader that I normally use to do my 'PU' ICs it is based on the same plan as my original photo form my first post.
Your SMD caps are probably ceramic.
Your drawing looks OK.
Don't you want your TTL connector to be similar to a FTDI SIP connector?
Why not make your board interface terminal standard to match the ICSP 6 pin layout?
Hi Larry,
I do apologise, I did a City & Guilds in the UK for Electronic Servicing Part I & II (which I received over 23 years ago) and did a course (and passed) from Cambridge University on Micro Electronics 29 years ago).
I make electronic projects for things around my house and beer brewing aids but can't remember most of what I did sadly hence at times I need my hand being held.
As to the capacitors, yes you are right, what I purchased was '500pcs/Lot SMD 0805 Ceramic Capacitors 0805 / 104PF 100NF Chip Capacitors'.
I found a web site with a capacitor conversion chart and saw that .1uF which you suggested is the same as 100nF, but 104pF is no where near that value. Am I correct in that, as the capacitors I purchased state they are 104pF/100nF. Does that make sense?
As to ICSP 6 pin layouts, actually that is a far better idea and would make a lot more sense, so have updated my chart.
An updated version
This is that last PCB that I created using the 'PU' version of the chip. It has 6 switches on it, a Tri-Colour LED and a 12v output for a fan. It is supplied by a 12v PSU and it is a liquid mixer. I want to make this board again with the 'AU' chip as should be able to make it smaller still. Currently it is 4.5 x 4.9cm
Thanks LarryD, sounds like a good plan. I have only ever made 6 PCBs before and 2 of them I am still awaiting for delivery. My 7th design will be this revised SMD version of a board, then a bubble counter/temperature probe for my beer brews so I can see the amount of CO2 the beer produces on ThingSpeak connected to my home WiFi.
Do you have any ideas why it needs the capacitors between the GND and VCCs whereas the 'PU' version doesn't? Or is it just the way the chip is made and it needs them as a result?
All ICs need 0.1uF between VCC pin and Gnd,
DIP have extra metal in the lead package that makes up the leg, so you might get a little capacitance there. SMD parts have less metal. 0.1uF will always help keep VCC more stable, really critical at higher switching speeds.
The "104" type labeling of capacitors can be confusing. It's actually like the resistor color code - the 3rd digit tells you the number of zeros, rather than being a digit of the value itself. So a cap labeled "104" is 100,000pf, which is the same as 100nF or 0.1uF.
Thank you CrossRoads for the info, I did wonder but now I know I will always put capacitors on them.
Thank you westfw, as I said, in a previous message, it has been over 23 years since I did my qualifications and to be honest only dable here and there and only started with Arduino 8 months or so ago and PCB design around 6 months ago.
It is all quite overwhelming to be honest, but I am loving the challenge. A friend who like electronics wants to have an Arduino with a temperature sensor that monitors his greenhouse and then at a set temp either turns on a heater or a fan. Then with a Real Time Clock it turns on (through a relay and water valve) a sprinkler over his plants. Then it will have a WiFi module so it can log in ThingSpeak what the temp and humidity is.
I said I would help create the wiring diagram and PCB then get it produced for him. Should be yet another fun project along with my own 3-4 that I have queued up.
Thank you so much guys for your help with this, I really do appreciate it.
Thanks LarryD, I will have to get one of those RTC and test it out. I have used the DS1307 before. Have you tried the DS1307? Would you rate the DS3231 over the DS1307?
Nice, saw them on AliExpress for £0.37 each for me, so $0.55 US dollars. Think I might buy 5 and give them a try. I have a few LIR2302 batteries knocking about that I can use.
I take it they connect wire and software wise the same as the DS1307?
WooleySheep:
lol, ian332isport, I think the course was called 724, I realy can't remember much about it sadly now.
I've a vague recollection that it was 224, but it was a long time ago. I remember quite a lot of stuff about repairing televisions though.
Getting back to your circuit. I've built a few boards with the AU chips. I always treated them as an Arduino Nano, and programmed with an Atmel AVRISP MKii programmer.
