Introduction: PIC Programmer Using USB-Serial Converter for 18F4550
Note : This hack is only needed if your usb-serial does not support the BREAK functionality. Else, it may work with as it is, with the usual programming software like PicPgm, WinPic etc.
Usually the DIY programmers like JDM do not work for usb-serial converters. Voltage levels, timings, and missing functionality like setbreak() causes issues. And some require a microcontroller that has to be programmed first, a chicken-or-egg problem. This hack provides a way to program the PIC using a usb-serial converter. Note that i have tested it only for the 18F4550. I found that a resistor of 1-5K is a must between DTR and PGD, it prevents a near short between DTR and PGD, when PGD is HIGH and ensures proper signal to CTS.(Thanks Darron from kewl.org for pointing this out). For safety, one might add the resistors to CTS and RTS as well.
Step 1: Details
Nowadays, computers do not have serial/parallel ports. Neither has my
laptop. Since my interest in PIC programming was temporary and for hobby purposes, i did not want to get a commercial USB based PIC programmer. Besides, where's the fun in that ? I decided to get a cheap USB-Serial converter, and see if it could make it work.
i used a Bafo Db9 USB-serial converter for around 200 Rs. and a python software for PIC programming at
i have blogged about it at :
It also works in HVP mode with changes to provide the high voltage.