Myalarm V-LED1 Manuel d'utilisateur télécharger pdf (Page 7)

via a connection to the TP104 on the

solder side of the MC13192-SARD

PCB. Ground is obtained from the

J101 BDM port pin 2. The signal is

connected to the ATD2 input on pin 3

of J105.

SOFTWARE DESIGN

For software development, I used

the Metrowerks Codewarrior develop-

ment environment that came with the

contest kit. Freescale’s Simple MAC

software provided everything neces-

www.circuitcellar.com

CIRCUIT CELLAR

Issue 194 September 2006

“N”

1 Byte

Netnum +48

ASCII

1 Bytes

“T”

1 Byte

devType+48

ASCII

1 Byte

“D”

1 Byte

Devnum+48

ASCII

1 Byte

“E”

1 Byte

Error+48

ASCII

1Byte

“A”

1 Byte

dAta

1 Byte

<CR>

1 Byte

<LF>

1 Byte

Figure 4

—Take a look at the wireless data packet format. Twelve bytes carry the network number, device type,

device number, error code, and data. All but the data have 48 added to push them into printable ASCII characters.

The letters between fields allow the detection of a valid packet. With the <CR><LF>, they make debugging easy by

dumping packets to a terminal window.

sary to get data flying between the

sensors and base unit. All I had to

worry about was the data format to

transmit the sensor information.

I decided on the data packet format

shown in Figure 4. NetNum is the net-

work number, which allows more

than one system to coexist. The base

unit reacts only to messages with a

matching network number and prop-

erly formatted data packet.

vType identifies the sensor type.

For example, the garage door sensor was

assigned a device type of 1. DevNum

allows more than one of the same sen-

sor type to be identified by the base

unit. Error is a “1” for a problem that

requires attention and a “0” other-

wise. Data is the actual sensor data.

The letters between fields and the

CRLF allow for the detection of a

properly formatted data packet. They

make debugging easier by allowing

the raw packets to be dumped out the

serial port and read with a terminal

program. (The first four fields are

bytes, and 48 is added to transmit in

readable ASCII characters.)

remainder of the software for

the remote sensors is simple set-up

and calibration code. It’s followed by a

loop that periodically wakes up,

checks the sensor, transmits the data,

and goes back to sleep. The remainder

of the base unit software is the set-up

code followed by code to monitor the

sensor data (and react appropriately)

and to monitor and process incoming

telephone calls.

IMPROVEMENTS

As usual, I thought of numerous

ways to improve this project even

before I finished. For instance, inte-

grating an Ethernet interface and

TCP/IP stack will allow for a web serv-

er that can be checked from anywhere

via an Internet connection. And since

text messages can be sent to some cell

phones by e-mail, this will allow

alerts to be sent right to a cell phone.

Additional sensors will greatly

expand the system’s capabilities. I

want to design a sensor that can

check the position of a deadbolt lock,

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