4.2.3 Crystal

The PIC18F47Q10 Curiosity Nano board has a 32.768 kHz crystal footprint made for standard 3.2 mm by 1.5 mm surface-mounted crystals with two terminals.

The crystal footprint is not connected to the PIC18F47Q10 by default, as the GPIOs route out to the edge connector. Some hardware modifications are required to use the crystal.
  • 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 RC0 and RC1
  • Connect the crystal by soldering on a solder blob on each of the circular solder points next to the crystal on the top side of the board, J210 and J211

Figure 4-4 show cut straps and solder points.

The PIC18F47Q10 Curiosity Nano board has been tested with a 7 pF equivalent load capacitance 70 kΩ ESR crystal (VMK3-9001-32K7680000TR) and 5 pF load capacitors. A similar setup is recommended when using a 32.768 kHz crystal with the PIC18F47Q10 Curiosity Nano.

The crystal has a cut-strap next (J209) to it, which can be used to measure the oscillator safety factor. This is done by cutting the strap and adding a 0402 SMD resistor across the strap. More information about oscillator allowance and safety factor can be found in the AN2648 application note from Microchip.

Table 4-3. Crystal Connections
PIC18F47Q10 PinFunctionShared Functionality
RC0SOSCO (Crystal output)Edge connector
RC1SOSCI (Crystal input)Edge connector
Figure 4-4. Crystal Connection and Cut Straps