Benefits of an accurate timing loop?

So I have been going through some data sheets today trying to pick out a crystal and a few caps for my atmega328 project. I have found a lot of threads on how to calculate the values of the capacitors but no one talks about the bennies of a well timed mcu. Most people are even adamant that it isn't important noting the 20% tolerance of capacitors. They usually use the 22pf caps because its a standard value close to one needed.

I was wondering if there any benefits to getting super close? My project uses a lot of communication through icsp and i2c. 8 to 10 nodes communicating wireless (nrf24l01 over icsp) with two nodes communicating through i2c and a webserver to boot. Would I see any performance increase from picking out tighter tolerance capacitors of the right value?

Odd values of caps dont seem to cost any more than standard values so I could care less if they aren't easy to find TBH. I also think I know someone with a high precision frequency counter so I can actually nail down the values on my particular PCB.

Over 45 years in electronics the only area where my experience found oscillator accuracy was important was in VHF and UHF radio and test equipment. Trimming capacitors and using crystal ovens were used. Then there was the advent of phase lock loops.

As far as the Arduino is concerned, the crystal is what is important. Some here don't use capacitors at all, relying on internal capacitance. I use 20-27pf, no problems yet

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Would I see any performance increase from picking out tighter tolerance capacitors of the right value?

No.

My project uses a lot of communication through icsp and i2c.

ICSP stands for in circuit serial programming and has nothing to do with the running of code. Do you mean SPI? That provides its own timing clock so accuracy is not important.

I2C provides it's own clock so the absolute frequency does not matter.

The only thing that is frequency dependent is asynchronous communications, sometimes called simply serial communications. That has to have a timing within about 3% of the nominal value in order for it to work without errors.

The only case where absolute accuracy is important is when you are wanting to time or measure some external frequency, or you want to keep a long term tracking of time that will not drift.

ICSP stands for in circuit serial programming and has nothing to do with the running of code. Do you mean SPI? That provides its own timing clock so accuracy is not important.

oops. yes that is what i meant. thanks for clarifying. Acronyms get me sometimes. I took the CCNA course once upon a time and all the acronyms for routing and switching protocols took up all the room I have for acronym memory storage.

That is handy to know SPI has its own independent clock. I knew the nrf24 modules has a crystal on it but I thought that maybe that was to keep the SPI device and the atmega328 on a somewhat synced schedule or whatnot.

thanks for the very helpful responses guys.

crs90:
That is handy to know SPI has its own independent clock. I knew the nrf24 modules has a crystal on it but I thought that maybe that was to keep the SPI device and the atmega328 on a somewhat synced schedule or whatnot.

I think you misunderstood. Mike is not saying that the SPI has its own independent clock. He is saying that the SPI provides its own clock to devices that are connected to it. In fact, the SPI circuit in the AVR derives its clock from a frequency divider connected to the main system clock.

crs90:
So I have been going through some data sheets today trying to pick out a crystal and a few caps for my atmega328 project. I have found a lot of threads on how to calculate the values of the capacitors but no one talks about the bennies of a well timed mcu.

The accuracy of the crystal and its tempco are more important factors - if you want accurate clock you’d
go for TCXO which is pre-trimmed.

Or use a crystal with good stability, like +/- 10 ppm (parts per million), so 16 MHz +/- 160 Hz, over a wide temperature range, as wide as -30C to +85C is available. http://www.digikey.com/product-search/en/crystals-and-oscillators/crystals/852333?FV=22c0011%2Cfff4000d%2Cfff8016d%2C3f40013%2C8640001&mnonly=0&newproducts=0&ColumnSort=1000011&page=1&stock=1&pbfree=0&rohs=0&k=crystal&quantity=&ptm=0&fid=0&pageSize=25&pkeyword=crystal SMD or thruhole?

CrossRoads: Or use a crystal with good stability, like +/- 10 ppm (parts per million), so 16 MHz +/- 160 Hz, over a wide temperature range, as wide as -30C to +85C is available. http://www.digikey.com/product-search/en/crystals-and-oscillators/crystals/852333?FV=22c0011%2Cfff4000d%2Cfff8016d%2C3f40013%2C8640001&mnonly=0&newproducts=0&ColumnSort=1000011&page=1&stock=1&pbfree=0&rohs=0&k=crystal&quantity=&ptm=0&fid=0&pageSize=25&pkeyword=crystal SMD or thruhole?

it will be thru hole. That +-10ppm thru hole on the link you gave me is the one I have in my cart at the moment.

thanks for all the good info guys.