16F88 bootloader

Started by upand_at_them August 8, 2004
All the examples I've seen for ICSP use a MAX232, but the PICAXE 18X,
which is a PIC16F88, has a simple two-resistor serial interface.

Any reasons why I can't use the resistor interface for PIC ICSP?

Mike




> All the examples I've seen for ICSP use a MAX232, but the PICAXE 18X,
> which is a PIC16F88, has a simple two-resistor serial interface.

Are you talking about ICSP or self-programming (bootloader)?

Do you care about reliability and reproduceability, or are you after the
lowest possible cost-per-unit?

Wouter van Ooijen

-- -------
Van Ooijen Technische Informatica: www.voti.nl
consultancy, development, PICmicro products



And don't forget that the MAX232 inverts, the resistors obviously don't, so you would have to take care of that somewhere. There are some hardware hacks with transistors that would do the inversion, but might it not just be easier to do it right.

Bob U.

At 08:59 AM 8/8/2004, you wrote:
> All the examples I've seen for ICSP use a MAX232, but the PICAXE 18X,
> which is a PIC16F88, has a simple two-resistor serial interface.

Are you talking about ICSP or self-programming (bootloader)?

Do you care about reliability and reproduceability, or are you after the
lowest possible cost-per-unit?

Wouter van Ooijen

-- -------
Van Ooijen Technische Informatica: www.voti.nl
consultancy, development, PICmicro products


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--- In , Bob Underwood <aa6bt@r...> wrote:
> And don't forget that the MAX232 inverts, the resistors obviously
don't, so
> you would have to take care of that somewhere. There are some
hardware
> hacks with transistors that would do the inversion, but might it
not just
> be easier to do it right.
>
> Bob U.


There are bunches of RS232 chips other than the MAX232. is there any
reason why that particular chip is required ?

Often I see Maxim chips in designs because the hobby market uses free
samples for the designs.

Is the MAX232 required for the design ?
What are the alternatives ?

Dave



> There are bunches of RS232 chips other than the MAX232. is there any
> reason why that particular chip is required ?

there is one good reason that chip is used very often (ok, three
reasons):
- it has been along a long time
- it is available from just about any supplier
- it is cheap

Wouter van Ooijen

-- -------
Van Ooijen Technische Informatica: www.voti.nl
consultancy, development, PICmicro products


I guess I was talking about both. I don't see why the ICSP interface
can't be the same as that for self-programming. Since no high
voltage is used they're both just sending logic signals.

Cost isn't really an issue since this is a single item project for
myself. I just want simplicity and low power consumption - the
MAX232 would consume power even when it's not used.

Mike

--- In , "Wouter van Ooijen" <wouter@v...>
wrote:
> > All the examples I've seen for ICSP use a MAX232, but the PICAXE
18X,
> > which is a PIC16F88, has a simple two-resistor serial interface.
>
> Are you talking about ICSP or self-programming (bootloader)?
>
> Do you care about reliability and reproduceability, or are you
after the
> lowest possible cost-per-unit?
>
> Wouter van Ooijen
>
> -- -------
> Van Ooijen Technische Informatica: www.voti.nl
> consultancy, development, PICmicro products





> I guess I was talking about both. I don't see why the ICSP interface
> can't be the same as that for self-programming. Since no high
> voltage is used they're both just sending logic signals.

Creating logic sequences with a serial port is not impossible but not
easy (or fast) either, so doing ISCP directly is not popular for serious
designs. It is used however for low-cost designs (check the ic-prog
website for designs).

The signals from a serial port are not logic-level, so you will need
some kind of level converter. A simple resistor will often work. Whether
that is enough for you is up to you to decide.

> I just want simplicity and low power consumption - the
> MAX232 would consume power even when it's not used.

You don't mention reliability, so I guess the resitor approach is good
enough for you :)

Wouter van Ooijen

-- -------
Van Ooijen Technische Informatica: www.voti.nl
consultancy, development, PICmicro products


it depends on what you mean by max232 vs other rs232 chips. There
are a number of clones (er, second source versions) of the max232
that are cheaper and work pretty much the same. You'll need to
distinguish between max232a and max232 clones, also. The non-A parts
use larger caps (1 uf vs 0.1 uf).

There are other rs232 drivers that should work just fine but I think
the max232 design has plenty of examples and is easy to add to a
project in a cook-book way so people just design it in. It doesn't
hurt that you can get max232 clones for under a $1 if you look
around. I bought a bunch off of ebay so that's what I use.

--- In , "Dave Mucha" <dave_mucha@y...> wrote:
> --- In , Bob Underwood <aa6bt@r...> wrote:
> > And don't forget that the MAX232 inverts, the resistors obviously
> don't, so
> > you would have to take care of that somewhere. There are some
> hardware
> > hacks with transistors that would do the inversion, but might it
> not just
> > be easier to do it right.
> >
> > Bob U. > There are bunches of RS232 chips other than the MAX232. is there
any
> reason why that particular chip is required ?
>
> Often I see Maxim chips in designs because the hobby market uses
free
> samples for the designs.
>
> Is the MAX232 required for the design ?
> What are the alternatives ?
>
> Dave





maybe this is a dumb question but 45 minutes of googling and
searching various archives leads me to it:

Is there a bootloader that runs on the 16F88?? I didn't see one. I
like the chip and a bootloader would be a huge benefit. Maybe not
quite enough for me to modify some other bootloader, though...\

Phil


> I guess I was talking about both. I don't see why the ICSP interface
> can't be the same as that for self-programming. Since no high
> voltage is used they're both just sending logic signals.

If ICSP interface is the same as that for bootloader, then why using
bootloader?

> Cost isn't really an issue since this is a single item project for
> myself. I just want simplicity and low power consumption - the
> MAX232 would consume power even when it's not used.

Use low power RS232 transceiver with shutdown and with receiver enabled
while in shutdown.

Regards,
Igor