Chip Programmers for PIC Microcontrollers and EPROM Chips

Chip programmers are used for do-it-yourself (DIY) projects such as the control boxes that I built in my last blog entry or to modify existing equipment. In fact, programming code onto a chip is a necessary prerequisite for many electronics.

Today, I'll explain how to build two different chip programmers. The first is for a PIC microcontroller, a chip which comes in many sizes. The second programmer is for an EPROM chip. Unlike PIC chips, EPROM chips aren't the sharpest tools in the shed. They just store the code. Still, you can find both types of chips in many electronics devices. In fact, you'll probably use something today that contains either a PIC chip or an EPROM chip.

The PIC Chip Programmer

If you hate acronyms as much as my editor does, you'll want to know what PIC stands for, If you're even more of a stickler than my editor, you'll know that PIC is not an acronym; the brand name is PICmicro. It is generally regarded that PIC stands for "Peripheral Interface Controller", although General Instruments' original acronym was "Programmable Intelligent Computer". That little fact and 65 cents will get you a cup of coffee. Sound like my editor needs one about now, but I digress. If you're not hung up on grammar, you'll just want to know that the PIC programmer I made is based on a JDM programmer. JDM are the designer Jans Dyekjaer Madsen's initials.

The JDM design interfaces with and is supposed to get its power from a serial port. There is one shortcoming with this design, however. The power output of my serial port just wasn't enough to put my chip into programming mode. Although JDM's design uses the negative and positive swings to produce a higher voltage for programming, there still wasn't enough juice for my poor little PIC chip.

Naturally, I made some slight modifications to the PIC chip programmer design. First, I added a power supply and a transistor to ensure that my poor little PIC chip got the correct voltage. I also added some light emitting diodes (LEDs) so I could see what the heck was going on in the circuit. Hey, how else would I know when the chip was being programmed?

Once I made these modifications, my first chip programmer worked like a charm. Now I was able to write code to my chips! If you're thinking about building your own, note that this is a very small circuit. I built mine on perforated board since I only needed to build it once.

The EPROM Programmer

EPROM, as my dear old editor wants me to tell you, is an acronym for "erasable programmable read-only memory". In case you're wondering, the "erasable" part requires ultraviolet (UV) light. But let's get back to the story.

My EPROM programmer was slightly more complex than my PIC programmer. It required some counter ICs (integrated circuits) to make it work. This is also a design I found online. It's laid out for a beginner, but I only used the schematic.

The EPROM programmer uses the parallel port instead of the serial port. Unfortunately, many of today's PCs (personal computers) don't have a parallel port. That's really kind of silly, because it's not like including a parallel port would impoverish the Silicon Valley moguls who are playing golf right now while you're at work.

Anyway, when I built my EPROM programmer, my PC had a parallel port. The computer that I have now does not. So, whenever I want to program more EPROM chips, I have to pull my old PC out of the closet. In case you're wondering, I decided to build this programmer on perforated board, too.

Both of these circuits have served me well over the years. I haven't used the EPROM programmer in a while, though. (I built it to modify some hardware that I no longer use.) I have used the PIC programmer many times, however.

Looking back on my life with chip programmers, I can honestly say that this was a great DIY project to get me started with microcontrollers.

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