Hi all! First post here, even if it's quite a long since I've read the first post on this forum!
Today I want to ask you directly something after I've tried to work it out for over two weeks. I've built an Atmega32u4 (the RC version) board working @5V and running with a 16MHz crystal. I connected the two pins of the crystal at XTAL1 and XTAL2 of the atmega and put two capacitors to ground, as described in the datasheet. My issue is that I can't get the crystal oscillate. Below I'll point out all my try:
- Tried to set the fuse and uploading a simple blink program with 22pF capacitors and 16MHz crystal. The fuse were set correctly, but I couldn't communicate with the chip via ISP after that.
- generated a 1MHz external square wave clock and set back the fuse to internal oscillator to debrick the chip
- since the crystal is designed for 20pF load I bought some 15pF and 18pF capacitors (considering some capacitance for the tracks) and set again the fuses to external oscillator. Bricked again the chip and had to use the external clock.
- Changed 3 different type of crystals, same results.
- XTAL1 on the scope shows a sine wave but very distorted, and I think also at a lower voltage compared to any working boards I've made in the past. The scope is not able to determine the frequency, but seems to show values near 16MHz, sometimes faster sometimes slower.
I use this fuse settings for the 16MHz clock, which I calculated online: lfuse:0x7f, hfuse:0x99, efuse:0xf3.
I'd like to try the full swing, since power consumption and electromagnetic disturb are not a big issue, but I don't know how to set it up.
Have you ever experienced something like this?
P.s. Here the crystal datasheet: Crystal