Puran's Blog: [DIY]+[PIC Programmer]+[IC-Prog]

Introduction
There are many kinds of PIC programmers in market, most of these use the parallel port, a serial port (COM port), or the USB but they are very costly and hobbyist like me can not buy such a costly programmer so i decided to make a cheap PIC programmer. Being a electronics hobbyist I believe in DIY (do it yourself) so here I glad to tell you that my programmer can be built easily. The programmer, which I built, does not need an external power supply it takes all necessary signals and power supply from RS232 serial port, and since there are only few parts, it is very cheap and easy to make. This PIC programmer is called "JDM programmer" and based on ICSP (In-Circuit Serial Programming) . This name comes from the name of Jens Dyekjar Madsen who devised this first. His homepage is here.

Advantage

This simple PIC Programmer will allow you to painlessly transfer hex programs to most Microchip PIC microcontrollers without sacrificing your budget and time
This PIC programmer is very cheap due to only few common parts are used.
It is in-circuit serial programmer so can be used to conveniently program PIC microcontrollers without removing them from the target circuit.
It can be built in very short amount of time.
This PIC programmer is compatible with a popular IC-Prog software that shows you a status bar of the programming progress.

How to build

Before you build this "PIC programmer", I recommend checking to see if there is enough output voltage at the serial port your personal computer. If TXD, DTR, and RTS do not have more than +7.5V(or -7.5V), this programmer will not work well, especially, with the latest laptop computers that using low power RS232 interface ICs. See follwing image to find TXD, DTR and RTS pins.

On the PIC side there are two possibilities to program the PIC microcontroller, socket and in-circuit. A socket programmer provides a way to connect just a bare PIC to the programmer and In-circuit programmers however connect to the PIC while it is connected to the target circuit. So ICSP allows programming of a PIC in circuit, avoiding the need to constantly take it in and out of the programmer and the subsequent bending of pins.

ICSP mode of programming

In ICSP mode of programming PICs are programmed using 5 signals. The data is transferred using a two wire synchronous serial scheme, with the clock always controlled by the programmer. The ICSP signals are:

*GND*:	Negative power input to the PIC and the zero volts reference for the remaining signals. Voltages of the other signals are implicitly with respect to GND.
*Vdd*:	This is the positive power input to the PIC. Some programmers require this to be provided by the circuit (circuit must be at least partially powered up), some programmers expect to drive this line themselves and require the circuit to be off, while others can be configured either way (like the Microchip ICD2). The Embed Inc programmers expect to drive the Vdd line themselves and require the target circuit to be off during programming.
*Vpp*:	Programming mode voltage. This must be connected to the MCLR pin, or the Vpp pin of the optional ICSP port available on some large-pincount PICs. To put the PIC into programming mode, this line must be in a specified range that varies from PIC to PIC. For 5V PICs, this is always some amount above Vdd, and can be as high as 13.5V. The 3.3V only PICs like the 18FJ, 24H, and 33F series use a special signature to enter programming mode and Vpp is a digital signal that is either at ground or Vdd. There is no one Vpp voltage that is within the valid Vpp range of all PICs. In fact, the minimum required Vpp level for some PICs can damage other PICs.
*PGC*:	Clock line of the serial data interface. This line swings from GND to Vdd and is always driven by the programmer. Data is transferred on the falling edge.
*PGD*:	Serial data line. The serial interface is bi-directional, so this line can be driven by either the programmer or the PIC depending on the current operation. In either case this line swings from GND to Vdd. A bit is transferred on the falling edge of PGC.