[NTLK] Developer Question: Serial Ports

From: Jake Bordens (newton_at_allaboutjake.com)
Date: Thu Jul 07 2005 - 15:34:58 PDT


I'm currently involved in some hardware development efforts,
specifically, something along the lines of a USB-001 (discussed
earlier on the list), a Bluetooth-001, or perhaps a combination of
both in one unit. My mainboard has a bad audio amp and I plan to
replace it soon. Hence, I'm more willing to put my trusty friend at
risk for hardware development purposes.

"But Jake", you say, "The internal connector is impossible to get".
"You're right," says I. I'm currently working on building my own
internal male connector out of common household items (and some CNC'd
parts.) So far, progress has been good... however, my "pins" are a
little big and tend to stretch out the female connector a bit.
Otherwise, they fit well. Still have some bugs to work out, but I'm
pretty sure I can make this happen.

Next problem... some holes in the documentation. And so the questions:

1. Does anyone how how to address the GPIO pin (pin 26) on the
internal connector? It supposedly can be configured as either an
input or output.

2. Is there a way to get the Newton to recognize port 3 in the list
of possible serial devices (along with Top Slot, Bottom Slot, and
Serial Port)? I'm hoping to make Port 0 a USB port and Port 3 a
Bluetooth module. However, if only custom software can address port
3, then I'd have to gang both on Port 0. See question 1: it becomes
necessary to be able to 'chip select' which device you'd like to deal
with, USB or Bluetooth

3. The PortSelect (Pin 1) and gpSerPortSelect (Pin 8) are outputs
from the Newt (inputs to the daughter card). Does anyone know how
they are toggled? As far as I can tell, the SER-001 ignores the
signal completely. I might just do the same, though a good citizen
would follow the spec and tristate the outputs of any daughter card
when these pins are low. The default seems to be low. Ignoring them
might be the best solution, since its possible that they're only
toggled when an endpoint is configured manually, or somesuch. (Its
been a while since I've dabbled in NewtonScript communications code)

Thats where I stand now. I might just start out and build a
prototype USB-001 board first. If successful, then move on to a dual
device with bluetooth. I am waiting for some parts (the USB chips
and some surface mount resistors and capacitors) but I hope to start
prototyping this weekend.

Any help and suggestions are always welcome.

Jake

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