Embedded Files
PIC18F2550 firmware v2.5 - 4 MHz - XTAL.hex firmware is intended for Velleman K8055-1 USB experiment board easy upgrade. It supports v2.5 firmware on PIC18F2550 Microchip microcontrollers that are clocked by a 4 MHz (XTAL) external crystal resonators. PIC18F2550 firmware v2.5 - all subversions.zip *.HEX-file pack from from Dowmloads section includes the following subversions for different frequencies and crystal types: 4 MHz (XTAL = tall crystal), 8 MHz (XTAL and HS), 12 MHz (HS = high speed), 16 MHz (HS) and 20 MHz (HS).
Velleman K8055 (K8055-1) experiment board is easily adapted to use PIC18F2550 microcontrollers. Just replace the 6 MHz crystal with a 4 MHz one. Choose a crystal with tall casing and accuracy of 4.000000 MHz. Next, remove R35 resistor.Program a PIC18F2550 microcontroller and you are done!
See PIC18F2xJ50 programming guide for more information.
Firmware v2.5 functionality is slightly limited due to PIC18F2550 simpler hardware. However, most of PIC18F2xJ50 firmware functionality works. There are also some changes in operation of certain functions, but it is easy to figure out, what has to be changed in a user application. A good example is detection of micro switches states on a K8055-1 USB experiment board. The test applications and the DLL, which were originally designed for PIC18F24J50, misinterpret micro switch I1 and swap switches I4 and I5, but a user application can still read them. Forthcoming versions of PIC18F2550 firmwares will have inbuilt compatibility functions, so they would operate almost seamlessly for the user application.
NOTE: A 4.000000 MHz XTAL crystal works perfectly with the same 33 pF capacitors as the original 6.000000 MHz XTAL crystal, so you just need to solder 4 contacts all together (2 to get crystal replaced and two to get the resistor out), unlike some other "open" K8055 projects which use different crystals (ex. 20.000 MHz) and they require for the capacitors to be changed as well. However, a higher frequency crystal does not bring any increase in performance, because a higher input frequency divider setting has to be used to get 4 MHz input frequency for the PIC18F2550 PLL to work.
ALSO READ:
- A simple PIC18F24J50 firmware upgrade or replacement with preprogrammed PIC18F26J50 adds many new functionalities to K8055N-2 experiment board - NO SOLDERING!
- Turn K8055 or K8055N into a microcontroller programmer
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