PICkit2 clone with reduced BOM

[jaka]

Hi all,

I know that I am 15 years late to 'build your own PICkit2 clone' party, but here goes.

I wanted to make a PICkit2 clone with reduced BOM. This doesn't mean minimal number of parts, but minimizing the number of different part types. Using PIC18F25K50 instead of PIC18F2550 allows getting rid of crystal and it's capacitors. I also eliminated all MOSFETs and diodes, they are replaced with common BJT types. Number of different part types was reduced from 33 to 20, without sacrificing any features.

All the design files, Gerbers, and firmware including full source is available on my web site http://kair.us/projects/pk2m_programmer/index.html

Too complicated? Try the minimal version shown below. It is probably the simplest PICkit2 clone so far, which uses only 3 components. Note that it only supports LVP and has other limitations as well, so it is like 'PICkit2 SNAP' 😀

[mariush]

You could probably reduce it further with a bunch of 1k , 10k and 22 ohm resistor networks (arrays of independent resistors) ... the even the 4.7k resistors could be 2 10k resistors in parallel

I wouldn't drop the separate crystal and its capacitors, seems like it would make it more flaky when it comes to usb.

ex
8 x 10k 2506 : https://www.digikey.com/en/products/detail/cts-resistor-products/742C163103JP/1124351
8 x 4k7 2506 : https://www.digikey.com/en/products/detail/cts-resistor-products/742C163472JP/1124336

8 x 10k 1506 : https://www.digikey.com/en/products/detail/panasonic-electronic-components/EXB-2HV103JV/285331
8 x  1k  1506 : https://www.digikey.com/en/products/detail/panasonic-electronic-components/EXB-2HV220JV/285299
8 x   22 1506 : https://www.digikey.com/en/products/detail/panasonic-electronic-components/EXB-2HV220JV/285299

[jaka]

Yes, combining resistor values using arrays is good idea. I have used that approach in some other projects. I especially like to use resistor arrays as feedback resistors for opamps, when minimal temperature drift is needed. Many resistor arrays have a specification for matching of temperature coefficient, so they cancel out nicely. This is cheaper than buying separate resistors with small PPM spec.

Actually, my original target for reducing PICkit2 BOM was to allow easy integration to PCBA test systems. So I wanted to use parts which could be already on the tester BOM.

Using crystal-less USB on PIC18F25K50 is not flaky. It has ACT (active clock tuning) which can sync to USB host clock. I have used it in several projects, including commercial ones, and it has been working without problems.