g. Do K8055 and K8055N boards run at 16 MHz?

The answer is YES! They perform flawlessly. If you are planning to program a microcontroller with a program code that requires a lot of processing time, operating frequency is certainly an important issue.

To run a USB capable microcontroller at 16 MHz, only a new HEX file, two new ceramic capacitors and a new crystal resonator are needed. Replace the 4 MHz crystal resonator with 16 MHz one and the two adjacent 27 pF capacitors with 18 pF capacitors. You can download HEX file from Downloads section and program it. If you use K8055 board with adapter, please select PIC18F2xJ50 adapter version of HEX file.

If you are using K8055 adapter board to replace PIC16C745 with PIC18F2xJ50, you only need to change the crystal resonator and the adjacent capacitors on the adaptor board (see photos below).

The Microchip recommended values of the capacitors are dependent on the resonator frequency:

Concerns

Please, note: K8055 and K8055N boards cannot run at higher frequencies with original Velleman programming. A special HEX file is needed to support each frequency. Microcontroller CPU frequency does not depend on the crystal oscillatory frequency, but rather on its FW. PIC internal frequency dividers and multipliers enable a wide range of choices. All the hex files provided on this website set PIC18F2xJ50 microcontroller CPU to run at maximum frequency of 48 MHz.

Velleman K8055 and K8055N boards are designed to meet USB 1.1 and USB 2.0 standard specifications. If PIC18F24J50 or PIC18F26J50 microcontroller runs at higher frequency, it draws more current. The upper limit for standard USB device is 100 mA and this is more than enough for the microcontrollers to run even at 48 MHz (the highest frequency). Your computer may only encounter problems when it is soft turned off. The USB specifications require all USB devices to draw no more than 2.5 mA during the soft off power state. Therefore it is advisable to disconnect the microcontroller before the computer is soft turned off, or alternatively the computer must be hard tuned off by a unplugging it from the outlet or switching off the power switch on PC’s power supply.