Summary of A pic programmer circuit based on AN589 using pic microcontoller
The article discusses a PIC microcontroller programmer circuit based on Microchip's AN589 application note, designed for parallel port programming. Although parallel ports are outdated and modern systems use USB-based programmers like PicKit3, this circuit offers a simple and reliable way to provide ICSP connections to a PIC microcontroller. The design includes modifications such as transmission line termination for long cables, an LM317 voltage regulator for stable 11.6V supply, power supply protection diode, updated voltage regulators, ICSP connector, power indicator LED, and component substitutions for ease of construction. Caution is advised to avoid damaging the PC’s parallel port.
Parts used in the PIC Programmer Circuit:
- PIC Microcontroller (target device)
- Parallel port cable
- LM317 voltage regulator
- LM78L05 voltage regulator (3-pin, 100mA)
- Power supply steering diode
- 74HCT244 buffer IC
- 10k ohm resistors
- LED (power indicator)
- ICSP connector
- Transmission line termination components (resistors/capacitors)
AN589 is microchip’s application note for a parallel port pic programmer circuit which I chose as I wanted something reliable to get up and running quickly.
Note: This page is left on site for legacy information that is applicable to older computers. These days PCs and laptops have only a USB interface so a parallel programming circuit is not useful. instead you should be using a PicKit3 (or maybe PicKit2) programmer which interfaces to the MPLAB X IDE and works well.
It is really quite a simple circuit and its main objective is to provide ICSP connections to your pic microcontroller.
Note: That the PGM signal is not provided – it’s not really necessary anyway as you can turn off PGM mode by programming the chip. For first use of a chip you will need to pull the PGM line low as PGM is enabled by the manufacturer.
PIC Programmer Circuit diagram
Disclaimer : If you build this circuit you must double check each connection to the parallel port cable to avoid damage to your computer. This includes checking for shorts between each pin at the parallel port on your circuit. For initial testing it is best if you use a spare (old computer). Building this project is your own responsibility and I can not be held responsible for any damage to your computer.
Modifications
It has a few modifications that are useful and easy to do:
- Transmission line termination – lets it work over a long cable.
- LM317 voltage regulator to get 11.6 volts and protect the circuit
- Power supply steering diode (stops you reverse connecting the supply).
- Changed LM340-5 to 3pin 100mA LM78L05.
- ICSP connector.
- An LED to show that power is applied.
- Changed 74LS244 to 74HCT244 because I had one handy!
- Standard 10k resistors instead of 2k – just easier if they are all the same.
For more detail: A pic programmer circuit based on AN589
