Proxim RangeLAN2 7920 Instrukcja Użytkownika Pobierz pdf (Strona 33)

D. DIGITAL COMPASS

1. Honeywell HMR3000

The Honeywell HMR3000 is a small single card electronic compass unit capable

of providing both heading and pitch information. The sensor on the compass is a

magneto resistive sensor, which utilizes the anisotropic magneto resistance of the ferrous

material of the sensor. The sensor material is placed in a basic wheat stone bridge

configuration and the heading is calculated. The card utilizes a 6VDC input and provides

a standard serial output to the user. The output is programmable to provide multiple

signals including pitch, roll, heading, or any combination of these required in various

formats. The output signal can be updated from six to three hundred times per minute

and in our application is set to one update per second.

Upon initial receipt the digital compass is programmed to provide a standardized

output for marine applications. The standard is from the National Marine Electronics

Association (NMEA) and is known as NMEA 0183. This standard programmed output is

a string, containing heading, pitch and roll information.

The string is formatted as follows:

$PTNPHTR,HHH.H,N,P.P,N,R.R,N*2C.

• $PTNPHR >> Header

• HHH.H >> Heading

• P.P >> Pitch

• R.R >> Roll

• N >> Mode, N=normal

The string is started with a standard header and is followed by the heading in degrees and

tenths of degrees (HHH.H), the next character (N) indicates normal operation, followed

by the pitch in degrees (P.P) finally followed by roll in degrees (R.R). Utilizing the

provided interface program a message can be sent to the compass modifying its output.

For our application, that string was parsed for the heading (HHH.H) ASCII information

only.

1 2 ... 28 29 30 31 32 33 34 35 36 37 38 ... 102 103

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Proxim RangeLAN2 7920 Instrukcja Użytkownika Strona 33