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This simple circuit can be used to program the PIC16F84 and similar "flash memory" type parts. It uses a cheap 555 timer IC to generate the programming voltage from a +5V rail, allowing the circuit to be powered from a computer’s USB port. The 555 timer (IC1) is configured as a free-running oscillator, with a frequency of about 6.5kHz. The output of the timer drives four 100nF capacitors and 1N4148 diodes wir-ed in a Cockroft-Walton voltage multiplier configuration. USB-Powered PIC Programmer Circuit diagram: USB-Powered PIC Programmer Circuit Diagram The output of the multiplier is switched through to the MCLR/Vpp pin of the PIC during programming via a 4N28 optocoupler. Diodes ZD1 and D5 between the MCLR/Vpp pin and ground clamp the output of the multiplier to about 13.6V, ensuring that the maximum input voltage (Vihh) of the PIC is not exceeded. A 100kΩ resistor pulls the pin down to a valid logic low level (Vil) when the optocoupler is not conducting. The circuit is compa...

Modern PCs rarely have a serial or parallel  port any more, to the great regret of any-one who experiments with microcontrollers every now and then. In the old days  it was very simple to use the parallel port  of a standard PC and program just about  any type of AVR microcontroller with it.  When you want to do that now, you’re first  obliged to buy a programmer that communicates with the PC via USB, which immediately raises the threshold of getting started  with these microcontrollers. The circuit presented here offers a solution to this. Simple USB AVR-ISP Compatible Programmer Circuit Diagram : As you can see from the schematic, this is  a very simple circuit, built around a cheap,  standard AVR microcontroller plus a handful of passive components. You may have  already observed that this microcontroller does not have a USB interface and the  circuit does not use a USB to serial converter either. The strength of this circuit is  found in the firmware. The USB interface  has bee...

This Multi PIC Programmer works as a usual JDM Programmer,  This Multi PIC Programmer works as a usual JDM Programmer. When the switch-2 is on, this Multi PIC Programmer changes into VPP-FIRST mode. The switch-2 will be used only when both INTOSC and internal MCLR options are selected (PIC12Cxxx,PIC12CExxx,PIC12F629, and PIC12F675,etc. Please refer to the data sheet of each PICs for more details).                                                                                                    ...