gnupic@linuxhacker.org

On Sunday 05 January 2003 16:27, somebody wrote
> I am thinking about doing a project using a SMT 16F877 part. This
> means I need to program it in circuit. From a quick read, I believe
> it is possible to program this part after it is installed in the
> final circuit by correctly setting up four pins or so. And that there
> is Linux software available for this.
>
> Am I thinking correctly? Any gotchas to this approach?
>
> Philip

Gotcha no. 1.  Microchip now prefer new designs to use the 16f877a, I 
am told. The 16f877 is 'no longer reccomended' for new designs.

You can use plcc parts with no gotchas - just an adapter for your 
picstart or whatever you use. Even I did that.

For the qfp part, there are gotchas all over the place. What you save 
with these is the plcc socket through holes. But there are smt plcc 
sockets. 

 The gotchas I spotted were
* Config word settings (LVP stuff). Security goes west
* First instruction in your code to be a nop (enables debug, I think)
I think you need access to 4 pins (or 3 & earth). You would want pads 
somewhere with vias, or a little plug
* I set up this way and the bloody thing went pulsing this one pin and 
looking for a program to run to be input to it. If I hadn't spotted it 
by chance... more hair would have been torn out.

In short you can make it happen if you read enough and really want or 
have to. I would go plcc. Buy/make  the adapter & extractor for plcc 
sockets and you'll never look back

-- 
	Regards,

	Declan Moriarty