Many thanks. I used to do a fair bit with electronics, many years ago. I'm slowly getting back into it, but things have changed a bit since my 6502 days. :)
I was not familiar with the R8C and related microcontrollers -- I've just been working on getting up to speed with the PIC family. What do you see as the advantages/disadvantages of the M16/M32/R8C vs. the PICs?
I also was not familiar with the VSK modules. They appear to be not extremely cheap, but certainly extremely convenient! Is there something similar I should be aware of that offers higher currents and/or multiple voltages?
Thanks again for your help!!
Andy
--- In Homebrew_PCBs@yahoogroups.com, DJ Delorie <dj@...> wrote:
>
>
> "awakephd" <a_wake@...> writes:
> > DJ, may I ask a couple of questions about your schematic? (May I ask
> > them even if I reveal all sorts of ignorance on my part? :)
>
> Sure.
>
> > I'm taking VSX-S3 near the upper right corner as a power supply that
> > converts the line voltage to 5V. Is this some sort of pre-packaged
> > module?
>
> Yes. Digikey part number 102-1802-ND. Ah - typo, it's a VSK, not a
> VSX. Fixed.
>
> > Am I right in thinking that you are detecting the 0 voltage
> > crossover in the AC using U4, and this drives an interrupt?
>
> Yes, but not quite. The capacitor and resistor drop the 120 vac down
> to a few milliamps through the opto, but the timing is such that the
> interrupt triggers about 45% of the way through the cycle. I use an
> interrupt-driven timer in the R8C to re-interrupt at the end of the
> cycle, which is the start of the next one.
>
> > What is the purpose of J1 -- for expansion, reprogramming, or ??
>
> Programming the R8C. It doubles as a serial console for debugging.
> See http://people.redhat.com/~dj/m32c/ for programming info. That
> connector is the "E8a" standard connector for r8c, m16c, and m32c (and
> I think r32c) chip families, although each chip uses different signals
> off it. The E8a itself only uses reset and mode, buy my linux-hosted
> programmer uses tx and rx as well.
>
> > Finally, I think the MAX6675 is the interface to the
> > thermocouple. Does this IC send the temperature of the probe over a
> > serial interface?
>
> Yes. Each 16-bit SPI read returns the actual temperature of the probe
> in Celsius (fractions of a degree, that is, plus some status bits).
> It's already done the conversion and cold-point compensation.
>