modifying a velleman K8048 by plugwash
I had several spare picsquirt boards from the
various prototying stages and i have a friend i'd like to inroduce to the
modern 18 series pics, but i didn't have any spare demo boards.
so i made the descision to buy a velleman K8048 (mainly because it was cheap
from rapid) and modify it for use
with the picsquirt. The plan was to remove (well not build, i bought the
velleman board as a kit not assembled) the inbuilt programmer (which was
serial and its software did not support 18 series pics), fit a polarised
molex kk connector for programming in the conviniantly supplied land
(intended for using the velleman board as an in circuit programmer but
perfectly suitable for the opposite role) and add some extra decoupling (in
the form of a surface mount capacitor directly between the socket pins)
so a PIC18F2550 can be run on the PLL. The run/program switch was bypassed
and the pullup to Vdd was increased to 47k to ensure the programmer could
pull it up to 12V. the replacement resistor is rapid
code 64-0118, the extra cap is rapid code 71-1380
Building mostly went to plan, there was one mistake in my layout
modification (caused by incorrect determination of the switch behaviour).
I have corrected this on the layout now and the changes are visible
here (on my board i used a different correction
involving one of the pads of the left out ZD1 because i lost a pad during
desoldering).
to solder the surface mount cap in i first soldered one of the relavent
pads on the IC socket, then i reheated that pad while introducing the cap
(with reverse action tweezers), then i soldered the other pad.
I have now done this mod twice and both boards work fine.
modified schematic
modified layout
