WinPicProg Forums

IanPegg · Joined: 11 Sep 2006 Posts: 45 Location: Northampton UK

Hi. I need to have up to 5 individual PWM outputs. I'm told that I could use 18F4455 or 18F4550 but I see that support for the 4550 is still beta and that I might therefore have problems. Are there any currently supported PICs that I could use instead? I guess I could possibly get awy with 4 PWM outputs at a pinch but 5 (or more) would be ideal.
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Ian

Nigel Goodwin · Posted: Thu Dec 21, 2006 11:31 am Post subject:

Not as I know off - I would suggest perhaps building an ICD2 clone, these are low cost and support new devices as MicroChip release them.

IanPegg · Joined: 11 Sep 2006 Posts: 45 Location: Northampton UK

Thanks Nigel. Just put ICD2 clone into google - seems to be hundreds out there. Any recommendations as to where to start?
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Ian

bbarney · Joined: 15 May 2006 Posts: 1

have a look at the Inchworm
http://www.blueroomelectronics.com/

Nigel Goodwin · Posted: Thu Dec 21, 2006 7:29 pm Post subject:

Daemons · Joined: 18 Jul 2006 Posts: 47 Location: Montreal, Canada

IanPegg · Joined: 11 Sep 2006 Posts: 45 Location: Northampton UK

Thanks guys. Given that funds (and time) are always in short supply, I'd like to build my own but don't want to have to go through the process a second time, at some point in the future. Although the limitations that Marc pointed out with the Inchworm may not be be an issue right now, who knows what I might want to do in the future. So, yes please Marc, I'd love to have a go at your design, especially if it lends itself to being built on vero board. What do I need to do for you to send it to me? Do you need my email address or can you post it here?

Meanwhile, I'm going to try and see if I can achieve what's needed by using sofware PWM and a 16F876 or 877 PIC.

Thanks to Nigels tutorials, I reckon it's possible but whether I'm clever enough is another matter....

I still intend to build an ICD2 clone so Marc, if you can send me the info, I'd be very greatful
Ian
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Ian

Daemons · Joined: 18 Jul 2006 Posts: 47 Location: Montreal, Canada

Daemons · Joined: 18 Jul 2006 Posts: 47 Location: Montreal, Canada

Ok. I made the changes needed to my design and made a PDF of it.

You can download it here: ICD2 Ser.pdf.

A few details about my version. I use a LM317 to generate VPP. Using the Digital pot (MCP41010) I let the 877 adjust the VPP voltage, as per the original ICD2. Only difference is I don't use a switching supply.

+5V is derived from VPP, so make sure you have a heatsink on the LM7805. Both regulators are TO-220 Versions Btw.

I changed the MAX chip back to MAX232 for you. I'm using a MAX233 which is the same thing, but without the need for the external caps. Only reason for using it is that I had a spare one. MAX232 is actually the original one being used.

I made mine on protoboard, so I didn't use T1 to power target VCC. Instead I just used a 2pin header with a jumper and I remove the jumper if the target has it's own power, or is not 5V (LV).

The ICSP header is a hooded 2x5 header. I use an IDC plug to connect to it on a 10 wire flatcable. Other end is connected to a keyed 5pin "Molex" type plug, the same kind Nigel uses for the tutorials. If you want a good example for the cable, have a look at the Inchworm assembly manual. Only difference with mine is that instead of cutting every 2nd wire short of the connector, I connect all of them with GND. This helps to eliminate problems of Xtalk with PGC<>PGD that you might otherwise encounter with cables longer than 6 inches. I would still keep the cable under a foot, to reduce capacitive load, but I've been told up to 5' is possible.

Thats all I can think about right now. Ask if you need anything else explained.

Marc

IanPegg · Joined: 11 Sep 2006 Posts: 45 Location: Northampton UK

Marc
Thanks very much for that. I'll look at is as soon as I get chance. Right now, any spare time I have (which ain't much) is devoted to sorting the problems with converting from "628" to the "876". Soon as I get that sorted, I'll look at taking the next big step up the learning curve (think I need to to learn to walk properly first).
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Ian