Datasheet

ADC
TERMINAL
V
1.5V
V 10.27V
0.146 0.146
u
ADC
V 0.7326mV 2048 1.5V

u u | u

REFA
ADC
12
V
3.0V
V ADCCODE ADCCODE 0.7326mV ADCCODE
4095
2 1
|
§ · § ·
¨ ¸
¨ ¸


© ¹
© ¹
ADC ADC ADC
TERMINAL
2
1 2
V V V
V
18000
0.146
R
105000 18000
R R
Data Logger, Motion Sensor, Temperature Sensors, CAN Transceiver, OLED, and SD Card (Schematic page 2) www.ti.com
Each of the 4 channels can measure 0-20 V with an approximate 0.01 V resolution. A voltage divider on
each channel scales the 0-20 V range on the terminal to the 0-3 V range of the 12-bit Analog-to-Digital
Converter (ADC) of the TM4C123GH6PGE microcontroller. Each scaled-down signal passes through a
unity-gain amplifier to provide a low-impedance source for the microcontroller’s ADC. Below are some
useful equations to keep on hand when using the four data logger channels.
(1)
(2)
For example, if the code read from the ADC is 2048, the voltage measured by the ADC is:
(3)
Therefore the voltage being measured at the screw terminal is:
(4)
CAUTION
Exceeding the input range on either the screw terminal or the ADC pins directly
can damage the analog circuitry.
2.2.3 9-Axis Motion Sensor
Included on the development board is an InvenSense MPU-9150 digital 9-axis (accelerometer +
gyroscope + compass) motion sensor.
Sensor Features
• Accelerometer
– User-programmable full-scale ranges of ±2g, ±4g, ±8g, and ±16g
– 16-bit resolution
• Gyroscope
– User-programmable full-scale ranges of ±250 °/s, ±500 °/s, ±1000 °/s, and ±2000 °/s
– 16-bit resolution
• Magnetometer
– Full-scale range ±1200 µT
– 13-bit resolution
The sensor communicates with the TM4C123GH6PGE through an I
2
C interface. The following signals are
used:
Table 2-4. 9-axis Motion Sensor Signals
GPIO Pin Pin Function Sensor
PD0 I2C3SCL SCL
PD1 I2C3SDA SDA
PB2 GPIO INT
Please refer to the MPU-9150 data sheet for more information about the sensor.
10
Hardware Description SPMU357B–August 2013–Revised March 2014
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