Limit - The upper limit frequency you want the VFO to reach. You will need to input the values of and recompile the software for your required VFO frequency: Specifically the FOSC_INTRCIO definition of the later version - change it to INTRC_OSC_NOCLKOUT for earlier versions of MPlab.Ī few words about the software. I use version 8.92 (which is the last of the old MPlab versions) and the problem relates to the 'include' file and the Config defines of those older versions. There have been a few cases of errors compiling files and it is caused by using an older version of MPlab. Note that to use the original software (or any of the modified versions I supplied prior to this update) with this pcb, fit the 100n capacitors marked as 1 on the schematic below and connect the encoder to inputs 'A' & 'B' and the Cal/Step switch to 'C'. I swapped the inputs around as I need a port line not associated with the encoder that can be either an input or output for an add-on that indicates the current step size via LEDs. The changes are - the inputs used for the Encoder and Calibration/Step switch have changed and a rearranging of some of the components on the pcb, plus, using a push button (or encoder push button), 3 step sizes of 10Hz, 1kHz and 10kHz are available. This has been kept as simple as, any buffering, amplification or filtering is left up to you to build to suit your purposes. It is a VFO that can be used just as an ordinary transistor/fet VFO would be. A Simple DDS based VFO using an 8-pin PIC.
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