so i want to use the atmega328 with out the shield and have seen numerous mentions of using a 16-22 mhz crystal across pin 9 and 10 to ground with 22 pf caps.
i can not find a 2 pin crystal locally and would like to finish the project tonight.
i have been able to find a 4 pin 16.384 mhz crystal
does anyone have an idea of how i could use this 4 pin instead of a 2 pin.
the crystal is ECLIPTEX EC1125 16.384M XX793
Page 2 of the datasheet shows the pinout. One pin is not connected, and another one is the case ground.
Then read this: I'm breadboarding an Arduino. How do I connect a 4-pin crystal oscillator? - General Electronics - Arduino Forum
And this: Compiling Optiboot - ATmega328P at custom frequency
Pieter
If you use a 16.384Hz crystal then all the timings of millis() and micros() will be wrong.
Have you considered running the Atmega 328 using its internal 8MHz clock?
...R
Have you considered running the Atmega 328 using its internal 8MHz clock?
...R
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Robin2:
Have you considered running the Atmega 328 using its internal 8MHz clock?...R
i did but i have read several post indicating it is not good to use the internal one as it is not very reliable.
hunicombs:
Have you considered running the Atmega 328 using its internal 8MHz clock?...R
i did but i have read several post indicating it is not good to use the internal one as it is not very reliable.
I have several projects that use it and I have never had a problem.
...R
PieterP:
Page 2 of the datasheet shows the pinout. One pin is not connected, and another one is the case ground.
Then read this: I'm breadboarding an Arduino. How do I connect a 4-pin crystal oscillator? - General Electronics - Arduino Forum
And this: Compiling Optiboot - ATmega328P at custom frequencyPieter
thank you for the links maybe i was premature in posting as i picked up the crystal on my lunch break and have not been able to research it yet.
What are you trying to do with your standalone circuit in the end?
Is this a time critical project?
I have created a couple custom circuits that used the internal 8MHZ clock.... and I never noticed any issues.
(but these were created to be used as Spider-Man webshooter props..so nothing really timing critical/related)
xl97:
What are you trying to do with your standalone circuit in the end?Is this a time critical project?
i am making turn signals to make my UTV street legal. so the need to blink at a regular rate so far with my program using it on the arduino shield it works great i was going to mock it up and a bread boars tonight with out the shield to see how it works out.
The inaccuracies of the 8MHz clock will be insignificant to a turn signal.
A bread boar sounds difficult. The circuit is built on the back of a pig?
Here is a complete breadboard duino walkthru with easy-use software that can ID many AVR's.
But his crystal like mine has 2 leads.
hunicombs:
i am making turn signals to make my UTV street legal. so the need to blink at a regular rate
The 8MHz clock will be fine for that. The human eye won't notice any difference.
...R
The internal oscillator is known for inaccuracy (it's calibrated to within 1% or so), not for it's instability (well, temperature and Vcc do affect its frequency but you won't notice it).
Lots of projects use the internal oscillator. Timing is accurate enough for the vast majority of projects, and definitely for a turn signal which just has to be within some large margin. To any human observer it will look perfectly regular.
hunicombs:
i am making turn signals to make my UTV street legal. so the need to blink at a regular rate so far with my program using it on the arduino shield it works great i was going to mock it up and a bread boars tonight with out the shield to see how it works out.
If the board clock may be off by 3 or 4%, what is the legal range of turn signal blink rates? Legalese is a kind of code, it should detail or refer to details in another document -- between cool morning and hot afternoon most blinkers should drift, temperature compensation circuits cost money!
I'm a bit surprised you don't just have a 555 circuit and switches to do this.
The legal range is defined in an SAE standard or whatever authorities in your country copied from the SAE.
From memory the variance allowed is huge. Anything between 0.25Hz to 4Hz is allowed. But it is a long time since I read the actual standard.
