2DIR pin. In this case, 2DIR is tied logically low, forcing
data to move from the 2Bx pins to the 2Ax pins. Pulling
both OE (Output Enable) lines to ground assures that all
1Bx and 2Ax output pins are permanently enabled at their
respective interfaces.
Removing the UART_EN jumper removes power from
the VCCB pin which disables the B portal. Disabling the B
port pins forces the B portal into a high impedance state
allowing us to access the ETRX357 I/O pins directly with
no interference from the disabled B portal.
Combined Interface Nuts and Volts
Looking at Photo 2, there’s not a lot we can say about
the Combined Interface device that you don’t already
know. Basically, we have the same minimal CP2102
installation, a user-accessible LED, and the ETRX357. The
right-angle header is the ETRX357 programming portal.
Note that the ETRX357 is powered solely from the
CP2102’s internal + 3. 3 volt regulator.
Now that you know what the Combined Interface
device is made of, you don’t have to tear the cover off of
yours. If you plan to follow the base plan of this month’s
discussion, start prying around the USB connector.
Automating the Five-In-One
The idea behind the Telegesis HA development kit is
to allow the HA designer to easily model and test the Five-In-One and Combined Interface devices without reading
any ZigBee manuals, writing any code, or building any
hardware. It’s rather obvious that the Five-In-One
development kit hardware is ready for action out of the
box. The software/firmware substitute isn’t as obvious.
Telegesis Terminal — which is a free download — provides
the software application emulation. Telegesis Terminal is a
PC application that allows the user to issue HA AT
commands via preprogrammed buttons. The user also has
the ability to easily create custom buttons.
A default Five-In-One Telegesis Terminal session is
captured in Screenshot 1. The Telegesis Terminal’s greatest
contributions to the development process are instant AT
command syntax verification and real time message
display. The Five-In-One device can be used in the
development process as a PC attached or embedded
attached device. To use the Five-In-One with a PC, we will
need to enable the CP2102 (UART_EN jumper in place)
and enable the external power via the power jumper. The
PC-enabled Five-In-One is shown back in Photo 1.
The Five-In-One you see in Photo 3 is wire-ready to
function as the target of an embedded host. To place the
Five-In-One in Photo 3 in embedded development mode,
we must use the male headers to attach external power
and signal. The signal interface to the CP2102 must be
terminated by removing the UART_EN jumper.
Recall that removing the UART_EN jumper removes
■ Screenshot 1. The
Five-In-One can be
completely
exercised using the
default command
button set. In
addition, the
can be used to
verify the correct
Telegesis HA AT
command syntax.
■ Photo 2. Your Combined Interface device comes as an encased dongle.
I tore the covers off of mine to show you its innards. If you look closely,
you can see the pry marks on the USB connector.
■ Photo 3. The Five-In-One can be put into embedded
debug mode by removing the power and UART_EN
jumpers. ETRX357 power and signal connections are
isolated to the male headers.
September 2013 59
