For my "Poor Man's TIVO" project I'd like to build a serial controlled IR
transmitter, I've already seen a couple of useful projects, including a
16F84 based serial port controlled transmitter, but just to sharpen some
programming skills (real rusty) I want to roll my own.

My basic game plan is to modulate the hardware PWM of a 16F628 and accept
commands via the hardware USART. The USART is pretty easy due to Fr. McGahee's
PICUART code and the Midrange manual and datasheet spell out the PWM for the
most part. However I did have one question on the PWM output and one on the
IR LED driver.

PWM: Both the midrange manual and the datasheet state:

   "Since the CCPx pin is multiplexed with the PORT data latch, the
    corresponding TRIS bit must be cleared to make the CCPx pin an output."

This makes perfect sense. However it is unclear if the TRIS bit is set that
that pin will in fact be turned into an input. It's implied but never stated.
Is that the case? If so then I can modulate the PWM simply by flipping the
TRIS bit.

IR DRIVER: I plan on using a standard NPN transistor to drive the IR LED.
a 1K base resistor should be fine for driving a 2N2222 into full saturation
under normal circumstances. However since I plan to float the base should I
use a pulldown resistor on the base also? What value would be appropriate if
so?

The absolute max current for the hideously expensive IR LED I got from the
RatShack specifies a 100ma max current. I plan to drive it at 80ma using a
47 ohm current limiting resistor.

Anyway if anyone has answers or other ideas I'd love to hear them.

BAJ

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