The current footprint accommodates a 32MHz crystal but needs to accommodate an 8-12MHz SMD crystal @3.3VDC. The common footprint size seems to be 5mm x 3.2mm dual pad. Representative crystals at Mouser
Traces to crystal should be the same length
Use a ceramic resonator over crystal because capacitors are built-in (reduced part count)
NOTE: IR data capture accuracy (i.e. learning) is affected by the sampling rate proportional to the clock speed - typical IR signal spacing is 17.5us to 27.7us. At 8 MHz the accuracy is limited to 8us and 4us on 16 MHz system. Ideally, we would run the IR Blaster at 16 MHz to allow increased accuracy during learning but requires a 5VDC supply to the ATMega328p.
bblacey
commented
9 years ago
The current footprint accommodates a 32MHz crystal but needs to accommodate an 8-12MHz SMD crystal @3.3VDC. The common footprint size seems to be 5mm x 3.2mm dual pad. Representative crystals at Mouser
NOTE: IR data capture accuracy (i.e. learning) is affected by the sampling rate proportional to the clock speed - typical IR signal spacing is 17.5us to 27.7us. At 8 MHz the accuracy is limited to 8us and 4us on 16 MHz system. Ideally, we would run the IR Blaster at 16 MHz to allow increased accuracy during learning but requires a 5VDC supply to the ATMega328p.