On Wed, 4 Mar 1998 00:12:59 -0500, Vu Hoang wrote: >Have any of you guys ever actually built a PIC programmer yourself or built >one of the PIC programmers from David Tait's site or any other site? > >If you did, could you tell me if it works or if it was difficult to do? I have recently built David Tait's TOPIC board for PIC 16C84. I wanted to find out about PICs, and a combined programmer and project board seemed a good way to go. Does it work? Yes, it seems to work well - I have to say seems because in the few weeks since I built it I have been too busy to play with it much, but I have programmed it with David Tait's test program, using his software to transfer the code from the PC, and it does what it is supposed to do. Was it difficult to do? No, but it does depend on where you're starting from - most things are easy if you know how and have the right tools. For anyone with experience of constructing electronic projects this is a fairly small and simple project to complete, but I'm not sure if I would recommend it as anyone's very first project since it does involve hardware, and software, and a communications link to the PC. The package provided (free!) by David Tait is excellent - it includes a written description, a circuit diagram, a photograph, a component layout diagram, a PCB foil pattern (300dpi, PaintBrush-compatible), PC software to drive the programmer and a simple test program. I have paid good money for much poorer materials, and I think we should grateful that people such as David Tait are willing to make their efforts freely available. If you can make a small, single-sided PCB then this is the way to go. If you can't, then other construction methods would probably work but a beginner might be better advised to buy a kit. In the UK, Maplin Electronics sell a kit based on David Tait's design - but I don't know anybody who has built one. There are various ways of transferring a design onto copper, including copying it by hand. I used photosensitive laminate with a transparency made by laser printing the image onto film. I had thought that I would able to use the clear film which is widely used for printing overhead projector transparencies, but the image quality was not good enough and I had to get hold of some matt film intended for pcb artwork. That was excellent. Of course, any film you use in a laser printer *must* be special film intended for laser or photocopier use - ordinary film will melt and could do expensive damage. At the first attempt I found that some of the pads on David Tait's pcb layout were a little delicate for my rough and ready manufacturing techniques, so I loaded it into PaintBrush and added some copper. The second one was fine. I don't intend this as a criticism of the design - I'm sure that if I had a vertical stand for my mini-drill and used good, sharp drills of the right size for each hole there would be no problem. David Tait gives the wiring details for a lead to connect the TOPIC to your PC's 25 way D-type parallel/printer port. With my setup it is more convenient to use a short adapter with a female 36 way Centronics connector which plugs into the end of a standard printer cable which is permanently connected to the PC. The connections are: TOPIC 10w IDC Connector 36w Centronics ------------- -------------- pin 1 pin 31 pin 3 pin 2 pin 5 pin 1 pin 7 pin 14 pin 9 pins 11 & 36 pins 2,4,6,8,10 pins 19 - 23 (all ground) As well as the software to drive the programmer, which is provided, you will need an editor to write your own programs and an assembler to prepare them for downloding to the PIC. The editor in current versions of MS-DOS is quite usable, and the MPASM assembler can be downloaded free from the Arizona Microchip website as can its user manual (DS33014F). Beware - the manual is a hefty 160+ pages in Adobe PDF format. Another useful document is the PIC16C84 Data "sheet" (DS30445C) - 109 pages including a lot of stuff you probably won't want but also including essential material such as descriptions of the registers and the instruction set. There are also some useful and instructive application notes on the site. If you have some low-level programming experience then the free documents may be all you will need, if not you will need to buy one of the beginners' books you will see referred to from time to time. Good luck! -- David Waterhouse