I need to know which Arduino boards use a quartz crystal for the MAIN processor instead of a ceramic resonator. Searching around so far I have only been able to identify the Leonardo and Due as having quartz crystals. Is there a list anywhere ((or can someone produce one) that gives this info for boards that are still available for purchase. It’s for a telescope controller BTW. Thank you.
The Pro Micro also has a quartz crystal.
One other thing you can do... on the UNO, the 16U2 that runs the USB interface has a quartz crystal. So you can use a USBASP to program the UNO so you don't need a bootloader, dedicate the 16U2 to becoming a timebase generator for the UNO.
Thanks, I did spot the Micro as well. I've just checked the schematics for some of the others, but apart from 32kHz crystals all the others seem to be resonators. So it looks like it will have to be one of these three, Micro, Due or Leonardo.
As for programming the 16U2 as a timebase, well I know my limitations!
I use 16 MHz quartz crystals on all the boards I offer. 328P, 1284P, 2560, 2561. Never a resonator.
I think that any board that can act as a HID uses a crystal. In that line, I would suspect all Teensies to use crystals as well.
Thanks for that, I’ll have a look at their site
Also a lot of UNO, Pro Mini and MEGA clones have a crystal.
The boards before the UNO (Diecimila, Duemilanove, NG, etc) had crystals. Perhaps you can find clones of them. If you get one with an ATmega168 you can swap in an ATmega328P with an UNO bootloader and have, essentially, an UNO with a crystal.
If you are using something for timing, particularly for date and time, you will want an RTC anyway. That gives you a precise timebase PLUS battery backup. The DS3231, for about $3, is a good choice.
What’s wrong with a 32kHz crystal? Many of the newer chips use a low frequency crystal with some sort of multiplier (dpll or dfll) to get their main clock.
Thanks for all the information. I have decided to go for a Leonardo in the first instance while I take time to get up to speed with Arduino programming, it's a bit different to Raspi Python or PIC assembler.
I'm now going to have a good look at parts of the code for the OnStep and rDUINOscope telescope controllers to get a starting point.
Thanks for now, but I've no doubt I'll be back sometime.