Information
PmodCMPS™ Reference Manual
Copyright Digilent, Inc. All rights reserved.
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Page 2 of 2
bus. To change the PmodCMPS from idle mode back into Single Measurement or Continuous Measurement mode,
the user must write to the Mode Register (0x02).
When reading data from the PmodCMPS, all six data registers, corresponding to the upper and lower bytes of each
Cartesian coordinate direction, must be read. Since the internal register address pointer automatically increments
after a register has been successfully read, it is possible to read from all six registers with a single command. An
example how this might look is given below:
Command byte
Address byte
0
0
1
1
1
1
0
1
(ACK)
0
0
0
0
0
0
1
1
(ACK)
MSB X
LSB X
SX
SX
SX
SX
sb
MSB
b9
b8
(ACK)
b7
b6
b5
b4
b3
b2
b1
b0
(ACK)
MSB Z
LSB Z
SX
SX
SX
SX
sb
MSB
b9
b8
(ACK)
b7
b6
b5
b4
b3
b2
b1
b0
(ACK)
MSB Y
LSB Y
SX
SX
SX
SX
sb
MSB
b9
b8
(ACK)
b7
b6
b5
b4
b3
b2
b1
b0
(STOP)
Table 1. Command and address bytes.
Note: SX stands for a sign extension of the sign bit (sb).
2.1 Pinout Description Table
Header J1
Header J2
Pins
Signal
Description
Pin
Signal
Description
1 & 5
SCL
Serial Clock
1
DRDY
Data Ready
2 & 6
SDA
Serial Data
2
GND
Power Supply Ground
3 & 7
GND
Power Supply Ground
Jumper JP1
4 & 8
VCC
Power Supply (3.3V)
Loaded State
SDA line uses a 2.2kΩ pull-up resistor
Jumper JP2
Loaded State
SCL line uses a 2.2kΩ pull-up resistor
Table 1. Connector J1: Pin descriptions as labeled on the Pmod.
The PmodCMPS also offers a self test mode to help calibrate any data that is being received from the module.
Any external power applied to the PmodCMPS must be within 2.16V and 3.6V; therefore, when using Pmod
headers on Digilent system boards, the supply voltage must be at 3.3V.
3 Physical Dimensions
The pins on the pin header are spaced 100 mil apart. The PCB is 0.8 inches long on the sides parallel to the pins on
the pin header and 0.8 inches long on the sides perpendicular to the pin header.