■ FIGURE 6. QuickStart header.
■ FIGURE 7. DipTrace Easy Order.
The /USB_PWR_EN pin can be used as an input or an
output. When reading this pin, a low indicates that the
USB interface is connected and communicating with the
host. On the QuickStart, this line is used to switch the
USB 5V power through a MOSFET to the 3.3V regulator.
By exerting 5V on this line, you can shut off that MOSFET.
I don't find this necessary, though, as routing 5V (or
higher) to the Vin pin causes a Schottky diode that is
inline between the MOSFET and the regulator to be
The XI pin allows you to provide an external clock
source to the Propeller. Before doing this, though, you'll
need to remove resistor R13 from the QuickStart to
disable the onboard 5 MHz crystal.
The /RTS and /CTS pins are not connected to the
Propeller; these come from the FTDI USB interface and
can be used when hardware flow-control is required.
The RESn pin is used to reset the Propeller. If you
want this capability from a custom add-on, you can pull
this line low through an NPN transistor or through a
normally-open pushbutton to ground.
TEMPLATES ARE FOR PCBS, TOO!
I mentioned that I like using templates — this applies
to PCBs, too. Some time after switching over to Dip Trace,
I downloaded the QuickStart files from Parallax and
stripped them to the bones. For my QuickStart shields, I
open the templates and then use File\SaveAs to my
project name. After saving, I link the new files by using
File\Renew Design From Schematic in the PCB editor.
After finishing my schematic, assigning patterns, and
double-checking everything, I save the schematic, go back
to the PCB editor, and use File\Renew Design From
16 May 2013
Schematic again. Bam! All of the parts from my custom
design are there, ready for me to place and route. By
using the template, I know the I/O connector and
mounting holes are right where they should be.
For those of you who love ExpressPCB (okay, I still
love it too, I just find it somewhat limiting for what I’m
doing these days), Dip Trace has recently been updated to
make the process of ordering a board much simpler.
In the file menu, you'll find Order PCB brings up the
dialog you see in Figure 7. Dip Trace uses Bay Area
Circuits and I have found the price, turn-around, and
quality excellent. For small items, I use this feature; for
bigger projects or where I need something else (like
blue PCBs for the project I describe below), I use Gold
Important Note: The QuickStart PCB template that
I've provided is right out of my computer and as such has
my name in the bottom solder mask layer — please delete
or change this to your own name before ordering PCBs!
EASY BAKE QUICKSTART SHIELDS
Last year, I put on my big boy pants by stepping up to
a professional level PCB development suite. This year, I
started making SMD PCBs. There was a discussion in the
Propeller forums about low volume SMD production and
a member suggested that the Cuisinart TOB-155 toaster
oven was a great solution for home SMD fabrication; he
even provided a recipe for "baking" boards.
The opportunity to go full tilt came through my friend
Steve Wang and his team at Biomorphs who were building
another display for Riot Games. The major lighting
animation is controlled using two EFX-TEK HC- 8+
controllers, but there are a lot of small elements not