DL4YHF frequency counter mod
From 5 to 6 digits

DL4YHF designed a nice little frequency counter, using PIC 16F628 and LED display. See his website.
VU3WJM designed a PCB, wich can be bought along with the kit on e-bay. Some modifications enabled the use of a sixth digit. Downside is the loss of the nice autorange function, but not a big problem if the counter is used in a monoband rig.

Hardware mods
All the PIC's outpout pins being used, I had to use the decimal point outpout to drive the additional digit.
Decimal points after MHz and KHz are now hard wired, and display forced to XX.XXX.X MHz mode.
Additional digit cathode is wired to RB1 and to last digit logic through a diode. Anodes are wired like other digits, in parallel.

Software mods
Display always begins with tens of MHz.
New figure is in display99 memory slot, just before display0.
New figure multiplexer is the same than the las digit one, new digit activation being done by lowering status of pin RB1 in the conv_char99 routine. For other digits activation this outpout is kept high by forcing addition of the decimal separator.
Modified code can be found here : counter.zip

The kit in its great package :


And now with six digits

Back of the modified PCB