A pic programmer circuit based on AN589

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.

Circuit notes

Transmission line termination

The transmission line termination lets you use the pic programmer circuit at the end of a long cable - I am using a normal parallel cable ~6 feet long. 

When I first tried to use it I got all kinds of random results so it is worth adding the termination.

Power supply regulators

The LM317 saves you needing an accurate bench power supply - you can use a dc power block - anything that supplies more than about 15V dc. If you don't use a 317 it's just too easy to accidentally apply the wrong voltage by turning the dial on a bench supply and frying your microchip. Using the 317 lets you put up to 35V into it (you shouldn't but you can).

Note: the LM317 and LM78L05 are standard components and are easy to find.

To save using odd resistor values I used a 10k and a 1k to set 317 output voltage. The equation for the LM317 is:

Vo = 1.25 * (1+R2/R1)

Vo = 1.25 * (1+10k/1k2) = 11.66V

5V power supply

Following on from this is the 5 volt regulator which is only used to power the LS244 buffer. Its just not worth using a Zener diode supply as the actual voltage at the Zener varies with the load (it's voltage is only specified for a constant current through it) you then need a transistor to isolate the Zener so its just easier to use the three pin regulator.

Note: The pin out of the LM78L05 is different to its larger counterpart the LM7805.

It is not a good idea to power the board from the programmer as :

• The 5V regulator should be designed for the target board i.e. heatsinking etc.
• You could get more noise into your circuit.

If you want to power your board from the programmer then change the 78L05 for a 7805 which can supply up to 1A but for higher current it will need a heatsink.

Buffer

The pic programmer circuit is a bit wasteful as it only uses two gates from the eight available in the LS244 but it's a cheap part anyway.

Q1, Q2 and Q3 can be replaced with any standard general purpose transistors (two npn and one pnp).

Software

You can use ICPROG with this pic programmer circuit. It erases, programs and verifies your pic microcontrollers.

ICPROG also controls resetting the microcontroller at the end of verify so after programming and verifying the program will start.

ICPROG is a good choice for programming software as it has many programming algorithms for many devices (not just PIC microcontrollers) and it is FREE. It also specifically supports this type of pic programmer circuit i.e. the AN589 pic programmer circuit.

Note: Double check the settings in ICPROG e.g. the HS setting for oscillator selection - otherwise you may find your microcontroller just sits there doing nothing!

Search:

Recent Articles

• 
• 

1. Arduino Nano PWM pins

   
   Arduino Nano PWM pins: Eight things you must know about PWM pins including how they affect timers.

   Read more

2. Learn How to Use the DHT22 with an Arduino; Full code examples included

   
   How to get accurate DHT22 digital humidity sensor readings with an Arduino. Did you know it also measures temperature as Well? Find out why, in this page...

   Read more

3. How to Use a PIR Sensor for Motion sensing using Arduino

   
   A PIR sensor lets your Arduino sense movement without contact. This tutorial covers PIR sensor basics, connecting one to an Arduino board and coding a motion detector.

   Read more

4. Arduino Hall Effect Sensor Tutorial: Detect Magnets Easily

   
   Arduino Hall Effect Sensor: Add magnetic sensing superpowers to your Arduino projects with an easy-to-use hall effect sensor. With full code and layout...

   Read more

5. INA219: Simple Arduino current measurement up to 3.2A

   
   INA219: How your Arduino can measure 3.2A at 100uA resolution, measuring the voltage and power consumption at the same time, using an I2C chip.

   Read more

6. TP4056: Your Essential guide to the LiPo Battery Charger IC

   
   Learn how to use the TP4056 properly. There's a right way, and a wrong way for safe charging of Lithium Ion batteries with this chip.

   Read more