Dumb Badge

The Dumb Badge, as it's name implies, is a simple, low performance member of the badge hierarchy. It simply transmits its fixed ID every few seconds then goes to sleep. It can't be reprogrammed on-the-fly and it does not respond to commands form the badge system.

We used it as a first test of the hardware and software, and as it turned out, to debug the compiler.

Specifications

Processor	PIC16C74A-JW
Cycle period	2.3 sec
Data rate	38400 bps
Duty Cycle	0.86%
Voltage	5V
On current	1.56mA
Sleep current	0.85mA
Size	54x86mm

Badge Frame Format

A frame consists of a sync byte followed by 26 data bytes. Future versions will use IrDA framing. Of course the frame format is subject to change without notice. The next change is likely to be to increase the size of X, Y and Z to 32 bits each to provide positions to 10cm resolution. Although 28 bits would provide sufficient precision, unfortunately 28 bits isn't a convenient size, hence we will use 32 bits.

Output Frame Format

OUT_PROTOCOL = 3 /* PROTO_DUMB */ Additional information is provided in the Smart Badge description.

#define OUT_SYNC	outframe_data[0]
#define OUT_LENGTH	outframe_data[1]
#define OUT_RANDOM	outframe_data[2]
#define OUT_PROTOCOL	outframe_data[3]
#define OUT_SEQUENCE	outframe_data[4]
#define OUT_ADDRESS0	outframe_data[5]
#define OUT_ADDRESS1	outframe_data[6]
#define OUT_ADDRESS2	outframe_data[7]
#define OUT_ADDRESS3	outframe_data[8]
#define OUT_STATUS	outframe_data[9]
#define OUT_TEMPERATURE	outframe_data[10]
#define OUT_LIGHT	outframe_data[11]
#define OUT_HUMIDITY	outframe_data[12]
#define OUT_ROLL	outframe_data[13]
#define OUT_PITCH	outframe_data[14]
#define OUT_YAW	outframe_data[15]
#define OUT_X1	outframe_data[15]
#define OUT_X2	outframe_data[17]
#define OUT_X3	outframe_data[18]
#define OUT_Y1	outframe_data[19]
#define OUT_Y2	outframe_data[20]
#define OUT_Y3	outframe_data[21]
#define OUT_Z1	outframe_data[22]
#define OUT_Z2	outframe_data[23]
#define OUT_Z3	outframe_data[24]
#define OUT_SOUND	outframe_data[25]
#define OUT_CRC0	outframe_data[26]
#define OUT_CRC1	outframe_data[27]

Resources

The complete badge design (schematic, artwork, C program and Intel HEX download file) is available for download.

To load the HEX file into a processor for the badge you will need the following:

PIC16C74A microcontroller
UV eraser
PICSTART programmer (or equivalent) and MPLAB IDE.
PC running Windows95 to run the MPLAB code and drive the PICSTART programmer

To modify the program you will also need the Microchip C compiler to go with the PICSTART system. This is an expensive item but you can download a free demo version that is limited to 256 output instructions. The demo compiler from the PICSTART CD is what we used for this version of the program (which is a tight fit on the 256 instruction boundary).

Contact

If you use the design or have any comments or suggestions we would like to hear from you.

H. W. Peter Beadle (Email: beadle@elec.uow.edu.au)

March 10, 1997

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