NUE- USB Card Manual, ver 1.34
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Copyright 2009, Midnight Design Solutions, LLC
The heart of the design is the Vinculum VNC1L FTDI controller chip. Although more expensive than
"USB bit banging" alternatives, the VNC1L chip provides support for the full USB protocol control, and a
DOS-like command line interpreter that allows easy writing and reading of a flash disk, making it a
relatively easy design-in for UART ports such as we have available on the NUE-PSK modem. (For a
great overview of the product, see the July 2007 issue 2004 of Circuit Cellar magazine
www.circuitcellar.com
). Additionally, the VNC1L chip offers Host mode support, which allows the USB
card to serve as the "serial interface" to a PC, providing a way to load modem software into the dsPIC as
before, as well as providing communications to other devices downstream.
A real-time clock/calendar (RTCC) function is optionally possible on the USB card in order to keep track
of date and time, even with the power removed from the modem. The concept is that the PIC monitors
the modem's UART port for an "RTCC data request", whereupon the PIC switches data path to send the
date and time information to the dsPIC. The new/replacement bottom half of the enclosure will continue to
have the battery cover plate present to allow accessing the coin-sized battery that powers the RTCC
circuit.
(NOTE: Although the RTCC circuit traces indicated in the schematic are indeed provided on pc
board, the RTCC functions and components are not provided in the initial NUE-USB cards being sold.
We did not have time to complete this lesser-important product capability, so we put the framework in
place with hopes that someone can step up to help with this Open Source design.)
III. ASSEMBLING the USB Card (from a kit)
This section is only applicable to those who have purchased the USB Card Kit.
If you purchased the
"assembled & tested" option for the USB Card, or if you had us do the "full factory upgrade" for your
modem, you of course do not have to assemble the kit or program the USB card, so you may skip ahead
to the section “Installing the USB Card” below.
1)
Attach U1. Use care to ensure that it is carefully aligned. Use desolder braid to remove excess solder
between pins.
2)
Attach all parts from the SMT card. C4, R12 and R13 are mounted on bottom of board (outlines shown
on top.)
3)
Attach crystal X1 slightly elevated so it touches no other parts.
4)
Attach all remaining parts. J1 mounts on bottom side, and P3 mounts on top. Check photos for proper
placement. Ensure that P1, P2, LED1 and LED2 are mounted flat and straight.
5)
Mount programming header P2 on bottom side by soldering short 90-deg end of connector to the 8
surface mount pads. Add solder to first pad then solder first pin while holding connector parallel to board,
pointing to same side as J1. Solder remaining pins to surface pads.
6)
Add the two ‘A’ jumpers. Using sharp blade, scrape the solder mask off the bottom side holes of each
set of jumper pads to expose the copper of the pad, then insert a bare wire across the pads from the top
and solder on bottom pads.
7)
Attach the two nylon standoffs using the screws supplied.
