The RDCM-803 Digital Compass Module

The RDCM-803 Digital Compass Module
Introduction
The RDCM-803 Digital Compass Module is a miniature low-cost orientation-sensing building block.
It indicates the orientation of the module relative to magnetic-north, as one of sixteen directions.
This is a successor to the RDCM-802 Digital Compass Module, and may be used to replace it.
Features
• Miniature size
26.3 x 26.3 mm (1.035 x 1.035 inches)
• Low power
3 mA typical, plus whatever current is sourced from the direction output pins.
• Wide supply voltage range
Can operate from 2.6 to 5.6 V.
• Easy to interface to
Output is via four pins, indicating a 4-bit binary value. “Grey encoding” is used, to ensure
only one bit changes between any two adjacent directions
• No moving parts
The RDCM-803 is entirely solid state, making it very robust
• Backward compatibility
The RDCM-803 can replace the earlier RDCM-802 8-direction compass module, with no
circuit changes.
• Improved performance
Compared to the RDCM-802 module, the RDCM-803 is:
o More precise:
16 directions, compared to 8.
o More accurate:
± 3 °, compared to ± 5 °
o More tilt tolerant: ± 60 °, compared to ± 10 °
o Lower power:
3 mA, compared to 10 mA.
Mechanical Dimensions
Pinout
Name
Direction
+5V
+3V
GND
D0
D1
D2
D3
STB
In
In
Out
Out
Out
Out
Out
RDCM802
equivalent
+5V
GND
D0
D1
D2
D3
-
Description
Power input. 3.8V to 5.6V
Alternate power input. 3.3V ±5%
Power and reference ground
Direction output (Most significant bit)
Direction output
Direction output
Direction output (Least significant bit)
Idles high.
Switches low while a measurement is being taken, then switches
high immediately after the direction output pins are updated.
MODE In
Mode select. Pulled down internally.
Low RDCM-802 compatible
(Magnetic North offset by 22.5° for 8 directions, or 11.25° for 16
directions.)
High Zero offset mode (for 16 directions only)
Note: The lightly shaded pins are new to the RDCM803 model. If left un-connected, the RDCM803
behaves the same as an RDCM802.
Absolute maximum ratings
Parameter
Voltage on 5V with respect to GND
Limits
-15 V to +6.5 V
Voltage on 3V with respect to GND
-15 V to +4.8 V
Voltage on MODE with respect to GND -0.3 V to 5V
(when powered via 5V pin)
(i.e. the voltage on the 5V pin)
Voltage on MODE with respect to GND -0.3 V to 3V
(when powered via 3V pin)
(i.e. the voltage on the 3V pin)
Direction Indication
With MODE pin low (i.e. RDCM-802 compatible mode)
8 directions
To detect 8 directions (the same as an RDCM-802), use just D2, D1, and D0
The angles in this table represent degrees
clockwise from the arrow on the PCB, to
magnetic north.
D2
0
0
1
1
0
0
1
1
D1
1
1
1
0
0
0
0
1
D0
1
0
0
0
0
1
1
1
Dir
N
NE
E
SE
S
SW
W
NW
Start angle
0
45
90
135
180
225
270
315
End Angle
45
90
135
180
225
270
315
360 = 0
So, to make north straddle your reference direction, the reference should be rotated 45/2 = 22.5
degrees clockwise from the arrow.
16 directions
To detect 16 directions, observe D3 as well. This then divides each direction in half.
With MODE pulled low
D3
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
D2
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
D1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
1
D0
1
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
Dir
N
NNE
NE
ENE
E
ESE
SE
SSE
S
SSW
SW
WSW
W
WNW
NW
NNW
Start
0
22.5
45
67.5
90
112.5
135
157.5
180
202.5
225
247.5
270
292.5
315
337.5
End
22.5
45
67.5
90
112.5
135
157.5
180
202.5
225
247.5
270
292.5
315
337.5
360 = 0
To make north straddle your reference direction, it should be rotated 22.5/2 = 11.25 degrees
clockwise from the arrow.
With MODE pin pulled high (i.e. RDCM-803 native mode)
Pulling the MODE pin high rotates the reference frame so that north DOES straddle the reference
arrow on the PCB. The 4 bit code for North will be output if magnetic north is 11.25 degrees either
side of the reference arrow.
D3
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
D2
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
D1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
1
D0
1
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
Dir
N
NNE
NE
ENE
E
ESE
SE
SSE
S
SSW
SW
WSW
W
WNW
NW
NNW
Start
348.75
11.25
33.75
56.25
78.75
101.25
123.75
146.25
168.75
191.25
213.75
236.25
258.75
281.25
303.75
326.25
End
11.25
33.75
56.25
78.75
101.25
123.75
146.25
168.75
191.25
213.75
236.25
258.75
281.25
303.75
326.25
348.75
Example usage
Minimum configuration, to display 8 directions on LEDs
(RDCM-802 compatible mode.)
Interfaced to a microcontroller. 16 directions with zero offset for north.
rdcm803 jul-2013