Date: Fri, 13 Sep 1996 11:49:31 -0500 From: Jim Robertson Subject: Re: Using the Picstart Plus to program other micro's? At 05:12 PM 9/12/96 GMT+2, you wrote: >------- Forwarded Message Follows ------- >From: Self >To: PICLIST >Subject: Using the Picstart Plus to program other micro's? >Date: Thu, 12 Sep 1996 17:07:40 GMT+2 > >I bought myself one of the new Picstart Plus programmers and is very >impressed with. This is almost a universal programmer in the true >sense of the word. Or is it? > >What I specifically like about the programmer is that they put DG411 >analog switches on almost all the pins, making it possible to cater >for almost any kind of pin configuration. The control is done by a >PIC17C42 (I think) which is connected via the RS232 serial port to >your computer. > >This brings me to an interesting thought... It really looks as if >this hardware should make it possible to also program other devices >on this programmer if one just replace the existing controlling micro >with another specially programmed one. I would particularly like it >if I can > program >the Atmel 89C20xx and 89Cxx devices. > >Has anyone else out there ever tried to do this? Is the schematics >for the Microchip Picstart Plus available anyware? It shouldn't be >too difficult to reverse engineer it, but I really don't want to do >that if someone else has already done this and I can just buy a >pre-programmed 17C42 to replace my existing one and wolla - My >picstart can now also program the Atmel devices! > >It would be interesting to hear what the programmer experts like Jim >and Antti think of this.... :) > >Rgds > >Werner > Werner, >(I hope you meant me when you said "Jim the programmer expert." I'm >not being presumptuous am I?) :-) Yes, I meant you. :) >I have not seen a PS + so I can only make general comments. First, I >would be surprised if the firmware chip is a 17C42 as it would take a >bit of effort to fit all the code into just 2k. Going by previous PS >16 efforts I doubt the Uchip employees would put this effort in. It is >certainly possible to fit the the required code in to a 17C42 but >somehow I suspect the chip is a 17C43. Could be a 17C43 or a 42. I didn't want to take label of the chip to look what was written underneath it, so I just assumed it was a 17C42. >Again, I am guessing, but I think you might be exaggrating when you >say there are DG411 switches on "almost all the pins." Exactly how >many are there and how many are connected to *unique* pins. Given that >you need two i/o lines for each switch to mean anything, there would >have to be plenty of additional i/o support, a 40-pin PIC could not >possibly handle it all. Exactly how much additional i/o support is >there? I see your point. There are six DG411 chips on the board and each DG411 contains four switches, so you were right in saying that not all of the pins are covered, but it probably still means that enough of them are. Anyway, the I/O support is handled by some74HC164 shift register and I don't quite understand why you said that two i/o lines are needed for each switch. >I think if you look harder at how and where the DG411s are connected, >you might be disillusioned somewhat, Right? I'll have use a multimeter and ring out what switches are connected to what pins before I can comment. >Never-the-less, it is possible to change the firmware and get the PS+ >to program lots of different devices. However, as for doing it >onboard, I have very strong doubts. I just don't think that you will >be able to program much more than PIC parts and maybe a few other >small devices like SEEPROMS, and KEELOC parts etc. Yeah, the one big problem is possible that the crystal ossiclator is on different pins for some of these other microcontrollers. >I realize the PS+ programs the 17C4x devices and these devices require >25 meaningful i/o lines. This would be just be enough to program some >smaller parallel eproms in theory. However, when you factor in the >additional multiplexing signals required, this is becoming very >complicated indeed. After all, the 25 i/o lines aren't all in the >right places are they? Probably not. >I have had a discussion with Antti about his pin driver idea. He loves >it, I don't. At the very best, a universal programmer based on a pin >driver concept would take at least 5 time longer to program than >specifically targeted code. Also, as Robert Lunn correctly pointed >out, there is still no guarantee that you can cover every possibility. >In practice, "final firmware" is a dangerous claim indeed. Unless they also allow for the firmware to be downloaded, but I could not see any eeproms or any other memory device that could hold the firmware externally to the controller micro. >The microchip Promate allows new firmware to be downloaded. This is a >far better way to guarantee future suitability. > >Anyway, hope I have given you have enough food for thought on the >matter. Yeah, I presume its not really worth the effort for me alone to try and fiddle with changing the firmware. It would be far cheaper and less of an effort to just buy or build another programmer for the other devices that I also want to program. I guess I was sort of hoping to get an easy answer for this, but it seems its not as simple as it looks. Thank you for your comments, Jim. Regards Werner. -- Werner Terreblanche Tel +27 21 7102251 Fax +27 21 721278 wterreb@plessey.co.za (work) OR werner@aztec.co.za (home)