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MAKE THE SMARTPIC SERIAL PROGRAMMER

by Duane Perkins

Start ý Commands and Response Codes ý The Electronics ý Construction ý Housing the Programmer ý Sources and PDF

HOUSING THE PROGRAMMER

For day-in-day-out use, it is nice to have the programmer in an enclosure. A 5.25" floppy drive enclosure is eminently suitable. You will also need a 3.5" floppy drive adapter kit. The parts list is available for downloading so you can check for a source. The small board (shown in the downloadable figures) will fit in the bezel supplied with the adapter kit.

The cutout for a floppy drive will have to be enlarged to accommodate the ZIF sockets. Cut a piece of sheet metal to serve as a base for the programmer board and a means of attaching it to the floppy drive adapter base that fits into the enclosure. The sheet should measure 5.2" ý 5.4". Bend down the tabs on the adapter base so the sheet will lie flat on them, leaving enough space for the heads of sheet metal screws below the tabs and about 1.25" of headroom above the tabs.

Place the sheet on the tabs leaving adequate space in front of the enclosure for a connector cable, then mark and drill the sheet for four sheet metal screws to attach it, using four of the tabs. Align the programmer board squarely over the sheet, then mark and drill the sheet for 6-32 machine screws. Use spacers between the board and the sheet, being sure to allow enough distance so the sheet metal screws will not touch the board.

Use a 10-pin dual-inline header connector and ribbon cable to provide connections between the programmer board and the board with the ZIF sockets. Solder the ribbon cable leads directly to the pads on the solder side of the ZIF socket board. You can devise some means of attaching the cable to the board other than the solder connections (even just a dab of epoxy cement will do).

The ZIF socket board can be attached to the bezel with 6-32 hardware or, if you like, a mini toggle switch and LED holder can be used to provide for power switching and a power-on indicator. Route the leads to the switch, well away from the ZIF sockets. R19 and J4 provide a handy current source for an LED. A Radio Shack 273-1365 transformer fits nicely in the rear end of the enclosure. The pinout of the header is shown in Table 2. Cut off pin 2 and insert it in the header connector so that it cannot be connected incorrectly.

IN CONCLUSION

The design of this programmer provides the most functionality for the least cost and conforms to Microchip specifications within the limits of its intended use. The V_DD levels are not precisely controlled and are limited in range, but satisfy the requirements for a developmental programmer that will not be used for production programming where more stringent demands must be met. Users experimenting with PIC16Cxx microcontrollers should find it more than merely adequate.

Microchip recommends that the window of an EPROM device be covered during reading or programming. If you experience problems, especially with a 40-pin device such as a PIC16C74, use a piece of masking tape backed with a small piece of aluminum foil. However, later devices with the A suffix (i.e., PIC16C74A) do not have this problem.

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