Texas Instruments TMP116METER-EVM User Manual
User's Guide
SNOU160–April 2018
TMP116METER-EVM User's Guide
The TMP116METER-EVM provides the user with an easy-to-read LCD screen while using the TMP116 for
measurement of ambient air temperature. The EVM measures 1.83 in × 1.45 in, so the system is fitted to
a small form factor for further convenience in space-constrained environments. The onboard
microcontroller (MCU) communicates with the temperature sensor using I2C communication protocol and
displays the measurement onto an LCD through SPI protocol.
Contents
1 Introduction ................................................................................................................... 1
2 Setup and Test Results ..................................................................................................... 4
3 Schematic and Bill of Materials ............................................................................................ 6
List of Figures
1 TMP116METER-EVM Front View ........................................................................................ 2
2 TMP116METER-EVM Back View ......................................................................................... 2
3 Software Flow Chart ........................................................................................................ 5
4 System Current Consumption.............................................................................................. 6
5 TMP116METER-EVM Schematic ......................................................................................... 7
Trademarks
All trademarks are the property of their respective owners.
1 Introduction
The TMP116METER-EVM comes pre-loaded with firmware that ensures successful operation upon
connection of the coin cell battery. Because the MCU is flashed using JTAG protocol, the test, reset, and
ground pins are broken out to a three-pin header for the user to have the option to flash the
MSP430FR5969 MCU. The device features three push-buttons: Button S1 functions to perform RESET,
S2 switches the temperature display format on the display (Celsius or Fahrenheit), and another button
(S3) can be programmed by the user. Test points are provided for the user to probe the clock and data
signal lines corresponding to I2C data transfer in addition to power and ground probe locations.
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Introduction
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Figure 1. TMP116METER-EVM Front View
1.1 Features
Low-power, high-accuracy temperature sensor: The TMP116 offers 16-bit resolution with an accuracy of
±0.2ºC (from -10ºC to +85ºC).
Ultra-low-power MCU: The MSP430FR5969 can operate from 1.8V to 3.6V while consuming 0.4 µA in
standby and 0.02 µA in shutdown.
Coin Cell Operation: CR2032 supplies 3V with a nominal capacity of 225 mAh
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Figure 2. TMP116METER-EVM Back View
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1.1.1 TMP116 Temperature Sensor
The TMP116 sensor measures the ambient air temperature with high precision and low power
consumption. This device provides a 16-bit temperature result with a resolution of 0.0078°C without
calibration. The TMP116 units are 100% tested on a production setup that is NIST traceable and verified
with equipment calibrated to ISO and IEC 17025 accredited standards. The sensor comes in a WSON
(2.00 mm × 2.00 mm) package and consumes minimal current that, in addition to providing power savings,
minimizes self-heating and improves measurement accuracy. The TMP116 operates from 1.9 V to 5.5 V
and typically consumes 3.5 µA.
1.1.2 MSP430FR5969 Mixed-Signal Microcontroller
The MSP430FR5969 is an ultra-low-power MCU that is optimized for lowered energy budgets in end
equipment.
The device is a member of the MSP430FR59xx family of ultra-low-power mixed-signal MCUs featuring
generous FRAM capabilities to enhance low-power designs in addition to intelligent peripherals to allow for
varied application implementation. Updating FRAM takes 100× less time than DRAM, and there is no preerase required. In addition, FRAM includes faster write speeds, unified memory, and low-energy writes.
Unified memory refers to program, data, and storage registers in one single place, which expedites the
software run. Because of its fast write speeds, FRAM has near infinite endurance. In a remote sensor,
data could be written more often for improved data accuracy, or it could collect data for longer. Due to the
lack of a charge pump, FRAM enables lower average and peak power during writes. FRAM is also
nonvolatile (that is, retains its contents upon power loss). Using the MSP430 MCU with FRAM allows for
on-the-fly writes, as opposed to buffered in RAM. The bitwise programmable memory can be used at the
programmer’s convenience for data or program storage. FRAM also offers advantages in security and is
inherently more secure due to its makeup. Also, de-layering is not effective. In comparison to MCUs with
flash, FRAM:
• Is very easy to use
• Requires no setup or preparation such as unlocking of control registers
• Is not segmented and each bit is individually erasable, writable, and addressable
• Does not require an erase before a write
• Allows low-power write accesses (does not require a charge pump)
• Can be written to across the full voltage range (1.8 V to 3.6 V)
• Can be written to at speeds close to 8MBps (maximum flash write speed including the erase time is
approximately 14 kBps)
• Does not require additional power to write to FRAM when compared to reading from FRAM
Introduction
1.2 Applications
The primary application of this EVM is to showcase a low power solution for temperature monitoring by
utilizing low power-consumption devices.
A battery voltage monitoring system allows the user to implement in firmware. A potential divider serves to
feed an ADC-enabled GPIO of the MSP430 MCU. That way, voltage sags intrinsic to battery operation
over time can be monitored and optionally displayed along with temperature measurement results;
however, this requires firmware modification. VCCMonitor is calculated as follows:
Select R4 and R5 to provide appropriate drive current to the ADC. In addition, the system features a
reverse polarity protection FET applied to the battery terminals. This FET acts as a load switch in the
system. Looking at the schematic, the body diode of Q1 sits connected between the drain and source of
Q1. The anode is connected to the drain, while the cathode is connected to the gate. When the battery is
connected correctly, the body diode is forward biased and conducts current from the drain to the source.
Because Q1 is a P-channel MOSFET, the gate voltage is brought below the source voltage, providing the
correct turnon condition. When the battery is connected in reverse, the gate of Q1 is receiving a voltage
above the source voltage. Therefore, Q1 does not turn on and current is not passed to the load through
conduction of the body diode.
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Setup and Test Results
2 Setup and Test Results
2.1 Hardware
The TMP116METER-EVM requires a Panasonic CR2032 coin cell battery
which is not included.
NOTE: The TMP116METER-EVM requires a Panasonic CR2032 coin cell battery which is not included.
The TMP116METER-EVM includes:
• MSP430FR5969 MCU
• Three push-button switches
• TMP116 temperature sensor
• LSO13B7DH03 LCD
• 32-kHz FC-135 32.7680KA-A3 crystal
• Associated discrete components
• For a comprehensive list of all parts, see the Bill of Materials (BOM).
2.2 Software
This TMP116METER-EVM ships pre-loaded with software for its MSP430FR5969 MCU. When the battery
is loaded, the display shows a Texas Instruments splash screen and then proceeds to display the current
temperature and humidity. The rest of this section details the operation of the software.
Included with this reference design is a software package that contains a Code Composer Studio (CCS)
project designed for the MSP430FR5969 mCU. For proper evaluation, import the CCS project into CCS
v7.3 or later with TI Compiler v16.9.4.LTS or later.
After reset or power-on, several hardware initializations take place. All GPIO pins are configured as
outputs and driven to logic low to save power. The pins that are used are then reconfigured for their
intended purpose. The MSP430 MCU’s internal oscillator, known as DCO, is configured for 8 MHz and
connected to the internal signals SMCLK and MCLK. The external 32-kHz real-time crystal (RTC) is
connected to the low-frequency clock inputs (LFXT), so the LFXT is configured as the source of the
internal signal ACLK (Aux Clock). TIMER A is configured as a counter with ACLK as source. Conveniently,
a count of 32768 (215) is equivalent to 1 second, a count of 16384 (214) is equivalent to a half second,
and so on. The eUSCI B0 peripheral is configured for I2C communication with the TMP116 device. Finally,
the eUSCI A1 peripheral is configured for SPI use with the display, and the Sharp display is initialized.
The next step in the software is to begin the loop.
On each iteration, the MSP430 MCU begins by checking the state of the button S1 and setting the Celsius
and Fahrenheit variable. An I2C Write transaction is then performed to instruct the TMP116 to begin a
temperature measurement. This measurement takes a few milliseconds (for conversion time, see
TMP116x High-Accuracy, Low-Power, Digital Temperature Sensor With SMBus- and I2C-Compatible
Interface ), so the MSP430 MCU is configured for LPM4 during the down time. After TIMER A interrupts
and resumes, the temperature data is retrieved from the TMP116. The values for temperature are
converted to characters using the tmp-decode.c library. This library is designed to provide string
conversion without loss of 16-bit precision, but it can be adjusted for less precision. Finally, the
temperature string updates the display and the MSP430 MCU returns to LPM4 for 2 seconds before
looping.
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CAUTION
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Reset / Power Up
Toggle Celsius/
Fahrenheit
Check
S1
button
Setup MCU pins, clocks,
Timer A, I2C
Initialize Graphics Library
(GRLIB) and Sharp Display
Pressed
Trigger
Measurement
Sleep (LPM4) during
measurement
Retrieve
Temperature Result
Update Screen
Sleep (LPM4) for
2 seconds
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2.3 Programming
The TMP116 meter can be flashed or debugged using the Spy-By-Wire (SBW) interface. The
MSP430FR5969’s SBW interface is available at header J1 pins TEST and RST. Connect these pins, and
GND/VCC as appropriate, to an MSP430 or a standalone debugger such as MSP-FET. For more
information, see MSP Debuggers .
Setup and Test Results
2.3.1 System Current Consumption
Although the current consumption of the system in its inactive mode is clearly defined by summing each
inactive mode current specification in device data sheets, it is not so clear when the devices are active.
Therefore, this test is set up to measure the current consumption of the system in active mode. The
measurement is taken using a small series resistor connected to a simple instrumentation amplifier to
perform a differential measurement across the resistor. This arrangement is used because the standard
probes of an oscilloscope can only take single-ended measurements.
The below image yields the current consumption of the system while it is in its active mode.
Figure 3. Software Flow Chart
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