DESIGNCYCLETHE
ADVANCED TECHNIQUES FOR DESIGN ENGINEERS
■ BY FRED EADY
BECOME A WIZ WITH
WIRELESS ETHERNET DEVICES
Put on your pointy hat with the moons and stars on it! This month, we are
going to design and construct the first device of the next generation of
embedded wireless Ethernet devices. While we’re at it, we’ll also lay the
groundwork for incorporating Microchip’s 16-bit line of microcontrollers into
future Design Cycle projects.
THEN AND NOW
Five years ago, I introduced the AirDrop series of
embedded wireless devices. The AirDrop-P was based on
the PIC18LF8722 and used one of the then popular and
easy to find 802.11b CompactFlash Ethernet cards. The
CompactFlash Ethernet cards used by the AirDrop devices
were limited to those that were based on the PRISM
chipset. To that end, I devised a PIC firmware driver that
supported the PRISM II and PRISM III chipsets. Believe it
or not, I am still offering the CompactFlash Ethernet card
shown in Photo 1 to Nuts & Volts and SERVO readers via
the EDTP webstore at www.edtp.com.
Today, there are multiple vendors that offer their own
particular taste of embedded Wi-Fi. Having written two
versions of the AirDrop driver firmware and two
versions of EDTP Ethernet MINI TCP/IP code, I tend to
lean towards Ethernet hardware that does not require
the user (that’s you) to write specialized code to drive
the embedded Ethernet device. One such device is the
new ZeroG ZG2100M Wi-Fi module you see in the raw
in Photo 2. The ZG2100M mounts just like an IC and
contains most everything hardware and firmware that is
necessary to put the module on the air. Plus, we don’t
have to get a Master’s Degree in Computer Science to
use it.
THE BRAINS OF THE OUTFIT
■ PHOTO 1. Although still available from EDTP Electronics,
the decreasing availability of this CompactFlash Ethernet
card was the toll of the bell for the EDTP AirDrop series of
embedded Wi-Fi devices.
Despite the ZG2100M’s inert intelligence, the ZeroG
ZG2100M Wi-Fi Module must be told what to do and
when to do it. What better device to be in
charge than a 16-bit PIC microcontroller. The
16-bit PIC of choice for this application is the
PIC24FJ128GA006. This is the largest baby in
the PIC24FJ128GA010 family. Its datasheet
tells us that 128 KB of program memory and 8
KB of SRAM are crammed within the area of
the PIC24FJ128GA006’s 64 pins. Its assets are
common all along the many variants of the
PIC24FJ128GA010 family. For instance, every
PIC24FJ128GA010 family member contains 8K
of SRAM regardless of the microcontroller’s pin
count. The PIC24FJ128GA006’s timer count of
five is also identical to all of its 16-bit cousins.
TIMER1 is a 16-bit timer whose first love is
obviously to tick-tock and time events under
■ PHOTO 2. The ZeroG ZG2100M Wi-Fi Module
is more like an integrated circuit part as it is a
DIP (Dual Inline Package) device that is mounted
on a set of pads.
68
April 2010
