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USBtinyISP and EMS atmegaxx8 target board
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USBtinyISP and EMS atmegaxx8 target board

by ju2wheels on Sun Nov 19, 2017 3:02 am

Hi all, I bought the USBtinyISP and EMS atmegaxx8 to get into playing with atmegas and circuits about two years ago. It sat in my closet for a while and finally got around to assembling both.

The USBtinyISP and EMS atmegaxx8 went smoothly for the most part, but I have a question on the EMS target board.

While assembling the EMS target board, I was looking at the Mass AVR programmer guide to figure out how to assemble the components. In my EMS atmegaxx8 target kit that I bought from Adafruit, it came with two ceramic capacitors. Im confused as to why it came with two since the diagram in this guide shows it with a single ceramic capacitor and a ceramic oscillator. Also from a bit of searching, I see that others are using it successfully without the oscillator.

Was my kit supposed to come with an oscillator or was it just an extra capacitor thrown in there? Since others are successfully using this board without the oscillator, in what cases would I actually need the oscillator?

Thanks,

ju2wheels
 
Posts: 5
Joined: Sun Nov 19, 2017 2:11 am

Re: USBtinyISP and EMS atmegaxx8 target board

by ju2wheels on Sun Nov 19, 2017 7:33 pm

I contacted EMS and they sent me the following:

Whether or not you need a resonator depends on what you are doing with the board: If you are programming the fuses on the target AVR to expect a resonator there, then you do indeed want to have a resonator there. If you are programming it to run with the internal oscillator only, then it doesn't matter.

Doesnt explain when we actually need to populate the other capacitors (C1, C2, C3) on this board, but good enough to get me started.

[Edit] From some looking around, I think C1/C2 are only used if we use a 2pin crystal oscillator for XTL since it requires two capacitors instead of just using a single 3 pin ceramic oscillator.

[Edit 2] I think I solved my question on the extra capacitor as well. Im assuming the second capacitor I got was for C3 and I think thats used as a bypass capacitor and so is C4? So I guess the assumption is if we were going to use an AC power source instead of the 6 pin ISP input power source then we would at least have it?

ju2wheels
 
Posts: 5
Joined: Sun Nov 19, 2017 2:11 am

Please be positive and constructive with your questions and comments.