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Topic: Workshopping £1.40 Arduino-Compatible (£3.05 including USB!) (Read 5 times) previous topic - next topic


Thanks, Crossroads.

I did wonder whether wiring to ARef was an 'override' of the default voltage and whether GND just made its way through the chip internally. For Analog input sketches (which I haven't tried yet with this board) I would have had a nasty surprise.

I'm not sure what you're saying about Arduino D14-19 (which is I think the alter-ego of the Analog pins). Are you saying I can at least use them as digitals without ATMEGA PINs 20/21/22 being connected, or is there an interaction with the Analog reference pins even then?

So far I haven't needed to modify the signature information within the IDE to program these chips. I have seen similar instructions when you need to _flash_ the chips, but once the bootloader's on there (I use Optiloader for this), it seems to behave fairly well just treating it as an Uno. Maybe I will uncover some nastiness later when I start using different parts of the board because the signature's wrong. I'll keep an eye out and I have your instructions to follow up on just in case there are weird results.

Thanks for all the suggestions so far, everyone. Really valuable.

Coding Badly

Will you have any connections to 20/21/22, Avcc/Aref/Agnd, to support analog functions, or to use D14-D19?

AVCC and AGND are required for the processor to function correctly.  I vaguely recall that a bypass capacitor is recommended.  AREF can be left unconnected.


This is how I start every project I do with a '328.
I often leave off the Power LED.
Crystal & caps you're replaced with resonator, that's fine.
0.1uF/100nF cap are essential for Vcc, Avcc, and Aref if you want to use the internal ADC and get good results.

100uF, maybe get by with another 0.1uF if you have power coming in via CP2102 so its fairly clean.
IO, connect up what need.
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.


Thanks for the diagram, CrossRoads. Really useful for discussion.

Although the two caps on the power lines look like they're in parallel (equivalent to a larger capacitor), I guess the main thing is that they are near the respective pins, hence they are actually doing a different job.

Is it reasonable to squash them into a single cap, assuming that cap is on the path between the pins and the power source. I'm thinking to just run some lines over the top of the ATMEGA from VCC and GND to connect AVCC and AGND, given that VCC and GND are already 'protected' from source variation by a decoupling capacitor. I'm aiming at the fewer tracks and complexity the better, but don't want to make unacceptable/idiot compromises.

I was a bit confused by the line starting...
"100uF, maybe get by with"
...as I didn't know what part of the circuit it referred to. I wonder if some words went missing on this line when posting.



so whats the point of "shrimping" ones laptop? does the arduino interact with the OS or is it basically just powered from the laptop and used to do fun looking things?

I definately agree with helping kids to learn how to do electrical wizardry, and freecycle is a good place to start for those who are hard up, i wish the had it in Spain,

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