PIC18LF452 programming woes - ICSP

Ttelmah · Guest

Hum.
I had their older USB programmer (no ICSP), and it never worked properly. I could program just about a 18F452, but not the EEPROM. It also wouldn't do the fuses right. Three software updates latter, and it is sitting in my 'scrap' bin...
That having been said, try increasing the resistor on MCLR to 47K. Historically some USB programmers, have problems delivering much current to the programming pin, and if this was borderline, it might give unexpected problems.

Best Wishes

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

I didn't say anything in the documentation where it says it will do ICSP
at 3.3 volts. Maybe it's in the help file. I didn't install the program.

Also, I wonder if it's programming the Config bits correctly.
If Brownout is enabled and it's set for 4.2v, the PIC will be held in
reset when you run it +3.3v.

I suggest that you borrow the ICD2.

barkerben · Joined: 19 Jan 2006 Posts: 22

I'll try that and post here when I've done it. If it works, I'll have to splash out on a new programmer I guess :-(

Cheers,

Ben

Guest · Posted: Sat Jul 08, 2006 4:22 am

Ok... it turns out I needed to shorten my ICSP lead - now working fine :-)

One thing however - I am toggling all the pins on port A as a test, and they all work except fr A4. I suspect this means I have somehow damaged the channel, but could it be anything else? Does that pin have any special significance?

Cheers,

Ben

Ttelmah · Guest

Yes.
A4, is an 'open collector' output. It can only drive 'down' to ground. You need to add a pull-up resistor to this line, if you want it to go up.
Glad you have it working. Hopefully their software now does program the EEPROM right (you might want to test this at some point).

Best Wishes

Guest · Posted: Sat Jul 08, 2006 12:25 pm

Yes, everything seems fine. I bodged a sloution by connecting pin A4 to the nearby E0 with a smalll bit of wire...nobody can see it :-)

Only problem now is my max710 seems to be going a bit odd and having problems with load regulation. While it was giving a steady 3.33v, it is now giving around 3.15 even with minimal load. Inout voltage is 2.65, so it is trying to step up...

my 5v supply is doing its job fine though. Oh well, I'm probably sort ut out :-p

Cheers.

Ben

Guest · Posted: Sun Jul 09, 2006 6:14 pm

Oooo.... I think I may heve don somthing stupid. When I realised the problem with A4, I used E0 instead. But the signal is still connected to A4, so when I drive E0 high I am also driving A4 high. I suspect this might explain my strange voltage levels...

Ben

StuartH · Joined: 19 Aug 2005 Posts: 14 Location: W. Midlands, UK

Ben, just set A4 to float. (input). That should sort the problem without hardware modification.
Sorry I couldn't be more helpful on the DIY board.