Hmr3000 Hardware Interrupt Pins; Algorithm For The Non-Linear Heading Filter - Honeywell HMR3000 User Manual

HMR3000 User's Guide

5.0 HMR3000 HARDWARE INTERRUPT PINS

The following is the detail description of the Cont./Reset, Operate/Calibrate, Ready/Sleep, Run/Stop pins.
The order of precedence for operation of the switch input pins is as follows:
1. Setting "Cont. / Reset" low unconditionally holds the HMR3000 processor in its reset state. No other functions can be
performed until the switch is returned to the "Continue" position.
2. Setting "Operate / Calibrate" low (Calibrate) forces the processor into Calibrate mode. The "Run /
Stop" and "Ready / Sleep" switches are ignored in this mode. When the switch is set to the Operate position, the unit can
be in either mode depending on the "Select Mode" command bit that can be changed via the serial interface. The "Select
Mode" command bit is initialized to the Operate state on power up.
3. Setting "Ready / Sleep" low while the unit is not in Calibrate mode forces the unit into a low power state with
measurements and outputs suspended, and with serial inputs ignored. This switch must be returned to the "Ready"
position before a host processor can send a serial command. When momentarily placed in the "Ready" position, the
processor will run a complete measurement and output cycle (if in Run mode) before suspending operation. Mechanical
switch bounce on this input can be tolerated in the firmware.
4. Setting "Run / Stop" low stops any output in progress within one character time and prevents further output. When the
switch is in the Run position, the state of the internal Run/Stop command bit controls the unsolicited output. The internal
Run/Stop command bit is initialized to the settings saved in the EEPROM.

6.0 ALGORITHM FOR THE NON-LINEAR HEADING FILTER

The algorithm for the non-linear heading filter is:
Assume CH = current heading
SH = smoothed output
L = tuned setting (integer > 0, 0 = disable)
S = tuned setting (0 < fraction < 1, 0 = disable, max = 0.999985)
Calculate D = CH - SH (difference)
G = S + S * (D/L)**2 (saturate G as D/L gets large, S <= G <= 1)
SH = SH + D * G (note that SH = CH for G = 1)
These calculations are iterated at the 13.75 Hz rate.
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