5.2.3 Crystal
PIC16F17146 Curiosity Nano has a 32.768 kHz crystal mounted. The crystal used is a VMK3-9001-32K7680000TR in a standard 3.2 mm by 2.5 mm package with two terminals. The 32.768 kHz crystal is accurate to within 20 ppm.
The 32.768 kHz crystal is not connected to the PIC16F17146 by default, as the GPIOs are routed out to the edge connector. Some hardware modifications are required to use the crystal. Remove power to the board before starting any changes.
- The two I/O lines routed to the edge connector must be disconnected to reduce the chance of contention to the crystal and to remove excessive capacitance on the lines
- Disconnect the edge connector by cutting the two cut-straps on the bottom side of the board, marked RA4 and RA5
- Connect the crystal by soldering on a solder blob on each circular solder point next to the crystal on the top side of the board, J210 and J211
The crystal has a cut-strap next (J209) to it. This cut-strap can be used to measure the oscillator safety factor, which is done by cutting the strap and adding a 0402 SMD resistor across the strap. Find more information about oscillator allowance and safety factor in the AN2648 application note from Microchip.
Figure 5-4 shows the cut straps and solder points.
| PIC16F17146 Pin | Function | Shared Functionality |
|---|---|---|
| RA4 | SOSCO (Crystal output) | Edge connector |
| RA5 | SOSCI (Crystal input) | Edge connector |
