Hellio, I have a bunch of the samd21 processors I was very successful in putting a bootload as well as a bink sketch on the processor using the arduino zero bootloader. I'm with a help of a friend soon to build my own pcb for it.
My problem is I have a hard time soldering smd crystal. I was wonder If I follow the wiring for the crystal can I use one of the 2pin crystal with a 2 pin through hole And Would it work the same way?
Joseph
Sure. Don't forget the two required capacitors, typ. 30 pF.
Hello, Yes He has including them. He never design a micro processor before. But he has done a lot of relay board and a few other things. He is still new to all designing. I really want to see if he can do it.
He is following this Schmetic https://cdn-shop.adafruit.com/product-files/2843/Arduino-Zero-schematic.pdf.
But the crystal looks like it is using 6.8 Not 30 as you are saying to use. Should he be using 30 instead of 6.8?
The recommended crystal load capacitance is stated in the crystal data sheet, which includes stray PCB capacitance.
The capacitors are effectively in series, so the total load capacitance is the series combination of the two you use, with stray PCB capacitance in parallel to the series combination.
I don't have the link for the correct datasheet to take a look at. Can you please share with me the link?
I have no idea what crystal you have. If you don't either, buy a crystal with a data sheet.
I got them from mouser. This is the ones I have https://www.mouser.com/ProductDetail/ECS/ECS-.320-12.5-13X?qs=sGAEpiMZZMsBj6bBr9Q9aTum9kEjld92o7ROYXbf8uI%3D.
Then get the data sheet from Mouser. There should be a link on the product page. If not, ask.
Oh i see. I thought there was a arduino schmetic I need to look at.
A schematic is a diagram of parts and how they are connected.
A datasheet is detailed information on a particular part - usually electrical and mechanical. The datasheet you need in this case to find out what load capacitance is needed.
For your PCB design: keep the crystal close to the MCU, and the load caps right next to it. Keep traces as short as possible. If your load capacitance is much off, the frequency of the crystal may be off, or it may not start oscillating at all.
The data sheet for the crystal that was linked to is for a "tuning fork crystal". Completely wrong for any microcontroller.
I think the selected crystal will work fine on the RTC oscillator input. Caps should be about 22 pF each, and the board capacitance will add other few, so the total load will be > 12 pF.
I didn't know If I needed to go by the schematic from the data sheet of the crystal or what I found online. This is all new to me. I'm learning as I go along, I will make mistakes. But it's cool trying to learn to build my own PCB. and figuring out the traces and what not.
Thank you. That is what I thought as well. But I wasn't sure if 12pf was correct or not.
The data sheet says 12.5 pF.
I saw that. I just wasn't sure. Thank you.
The data sheet is your very best and most reliable source of information.
I did not understand the crystal was meant for a clock. Does the clock have any way to make corrections for the crystal frequency? If not and exact frequency is needed, several crystals might be tried to find a correct one for the device.
The RTC/reference clock oscillator on the SAMD21 processor. Sparkfun uses 2x15 pF on their SAMD21 breakout board.
Hello all, Thank you for the help and information. Should I be using a 12pf cap or what adafruit said and put a 15pf cap? If I'm going by the datasheet of the crystal then it is a 12pf cap.
