Texas Instruments MSP430i2040 User manual

MSP430i2040 Embedded Metering EVM
(EVM430-i2040SUBMTR)
User's Guide
Literature Number: SLAU587
August 2014

Contents
1 Getting Started .................................................................................................................... 6
1.1 Preface........................................................................................................................ 6
1.2 Safety and Precautions ..................................................................................................... 6
1.3 Package Contents ........................................................................................................... 7
1.4 Introduction ................................................................................................................... 7
1.5 Features....................................................................................................................... 7
1.6 Hardware...................................................................................................................... 8
1.6.1 Top View of the EVM............................................................................................... 8
1.6.2 Bottom View of the EVM........................................................................................... 8
1.6.3 Hardware Setup Procedures ...................................................................................... 9
1.7 Calibrator Software......................................................................................................... 10
1.7.1 Software Package Content....................................................................................... 10
1.7.2 Setting up the PC Software Tool................................................................................ 10
1.8 Instruments.................................................................................................................. 13
2 Operating the PC Software Tool........................................................................................... 14
2.1 Introduction.................................................................................................................. 14
2.2 Start Using the EVM ....................................................................................................... 14
2.3 Known Issues............................................................................................................... 18
3 Calibration Techniques ....................................................................................................... 19
3.1 Introduction.................................................................................................................. 19
3.2 Calibration Techniques .................................................................................................... 19
3.3 Calibration Procedures .................................................................................................... 20
3.3.1 Calibration of AC and DC Parameters ......................................................................... 20
3.3.2 Calibration of Compensation Resistance and Capacitance ................................................. 21
3.3.3 Calibration of Current AC Offset ................................................................................ 22
3.3.4 Calibration of Voltage AC Offset ................................................................................ 22
3.3.5 Calibration of Phase Correction ................................................................................. 22
3.3.6 Calibration of DC Parameters ................................................................................... 22
4 Serial Communication Commands ....................................................................................... 23
4.1 Introduction.................................................................................................................. 23
4.2 Communication Protocol .................................................................................................. 23
4.2.1 Polling Mode ....................................................................................................... 23
4.3 Commands.................................................................................................................. 25
4.3.1 HOST_CMD_GET_METER_NAME ............................................................................ 25
4.3.2 HOST_CMD_GET_METER_VER............................................................................... 25
4.3.3 HOST_CMD_GET_METER_CONFIGURATION.............................................................. 26
4.3.4 HOST_CMD_GET_RTC.......................................................................................... 27
4.3.5 HOST_CMD_ALIGN_WITH_CALIBRATION_FACTORS ................................................... 27
4.3.6 HOST_CMD_SET_PASSWORD................................................................................ 27
4.3.7 HOST_CMD_GET_READINGS_PHASE_n ................................................................... 28
4.3.8 HOST_CMD_GET_EXTRA_READINGS_PHASE_n......................................................... 29
4.3.9 HOST_CMD_SUMCHECK_MEMORY......................................................................... 29
4.3.10 HOST_CMD_CLEAR_CALIBRATION_DATA................................................................ 30
4.3.11 HOST_CMD_SET_CALIBRATION_PHASE_n............................................................... 30
4.3.12 HOST_CMD_GET_CALIBRATION_PHASE_n .............................................................. 31
2Contents SLAU587–August 2014
Submit Documentation Feedback
Copyright © 2014, Texas Instruments Incorporated

www.ti.com
4.3.13 HOST_CMD_SET_CALIBRATION_EXTRAS................................................................ 31
4.3.14 HOST_CMD_GET_CALIBRATION_EXTRAS................................................................ 32
5 Firmware and Embedded Metering Library API ...................................................................... 33
5.1 Introduction.................................................................................................................. 33
5.2 Firmware Structure......................................................................................................... 33
5.3 Toolkit Package............................................................................................................. 33
5.4 Metrology Computation Engine........................................................................................... 34
5.4.1 Background Process.............................................................................................. 35
5.4.2 Foreground Process .............................................................................................. 36
5.5 Embedded Metering Library API ......................................................................................... 37
5.5.1 Embedded Metering Library Function calls.................................................................... 37
5.5.2 Embedded Metering Library Callbacks......................................................................... 40
5.5.3 Application-Level Calibration Functions........................................................................ 41
A Example Application Code .................................................................................................. 48
A.1 Introduction.................................................................................................................. 48
A.2 Prepaing the Application Code to Run .................................................................................. 48
A.3 Downloading Without an IAR License................................................................................... 55
B Hardware Design Files ........................................................................................................ 58
B.1 Package ..................................................................................................................... 58
B.2 Schematic ................................................................................................................... 59
C EVM Specification and Performance..................................................................................... 60
C.1 EVM Specifiction ........................................................................................................... 60
C.2 EVM Performance.......................................................................................................... 61
C.2.1 Power Accuracy at Room Temperature........................................................................ 61
C.2.2 Accuracy vs Temperature at 220 V, 5 A ....................................................................... 63
D Running on MSP430i2040 and MSP430i2041.......................................................................... 64
3
SLAU587–August 2014 Contents
Submit Documentation Feedback Copyright © 2014, Texas Instruments Incorporated

www.ti.com
List of Figures
1-1. EVM Top View ............................................................................................................... 8
1-2. EVM Bottom View ........................................................................................................... 8
1-3. System Properties Window ............................................................................................... 11
1-4. Device Manager Window.................................................................................................. 12
1-5. Edit calibration-config.xml................................................................................................. 13
2-1. Calibrator Software Startup Window..................................................................................... 15
2-2. Meter Status Window...................................................................................................... 16
2-3. Meter Calibration Factor Window ........................................................................................ 17
2-4. Meter Features Window................................................................................................... 17
2-5. Meter Error Window........................................................................................................ 18
3-1. Front-End Interface Model ................................................................................................ 19
4-1. Polling Mode Data Frame Format........................................................................................ 23
4-2. Polling Mode Command Frame Format................................................................................. 24
4-3. Polling Mode Respond Frame Format................................................................................... 24
A-1. Project Options ............................................................................................................. 49
A-2. Optimization Options....................................................................................................... 50
A-3. Debugger Options.......................................................................................................... 51
A-4. Download Options.......................................................................................................... 52
A-5. Compiling the Application ................................................................................................. 53
A-6. Warnings .................................................................................................................... 53
A-7. Connecting EVM and FET ................................................................................................ 54
A-8. Code Downloading......................................................................................................... 54
A-9. Debugger Screen........................................................................................................... 55
A-10. EVM Running............................................................................................................... 55
A-11. Download File............................................................................................................... 56
A-12. Select File ................................................................................................................... 57
B-1. EVM Schematic............................................................................................................. 59
C-1. Power Percentage Error (%) vs Load Current (A) .................................................................... 62
C-2. Typical Accuracy vs Temperature........................................................................................ 63
D-1. IAR 5.5 Launch Window................................................................................................... 64
D-2. Open Workspace Window ................................................................................................ 65
D-3. Workspace Options ........................................................................................................ 65
D-4. Options Window............................................................................................................ 66
D-5. Config Tab................................................................................................................... 66
D-6. Selecting Default XCL File ................................................................................................ 67
D-7. Finishing the Setting Changes............................................................................................ 67
D-8. Saving the Setting Changes .............................................................................................. 68
4List of Figures SLAU587–August 2014
Submit Documentation Feedback
Copyright © 2014, Texas Instruments Incorporated

WARNING
General Texas Instruments High Voltage Evaluation (TI HV EVM) User Safety Guidelines
Always follow TI’s setup and application instructions, including use of all interface components within their
recommended electrical rated voltage and power limits. Always use electrical safety precautions to help
ensure your personal safety and those working around you. Contact TI's Product Information Center
http://support/ti./com for further information.
Save all warnings and instructions for future reference.
Failure to follow warnings and instructions may result in personal injury, property damage, or
death due to electrical shock and burn hazards.
The term TI HV EVM refers to an electronic device typically provided as an open framed, unenclosed
printed circuit board assembly. It is intended strictly for use in development laboratory environments,
solely for qualified professional users having training, expertise and knowledge of electrical safety
risks in development and application of high voltage electrical circuits. Any other use and/or
application are strictly prohibited by Texas Instruments. If you are not suitable qualified, you should
immediately stop from further use of the HV EVM.
1. Work Area Safety
(a) Keep work area clean and orderly.
(b) Qualified observer(s) must be present anytime circuits are energized.
(c) Effective barriers and signage must be present in the area where the TI HV EVM and its interface
electronics are energized, indicating operation of accessible high voltages may be present, for the
purpose of protecting inadvertent access.
(d) All interface circuits, power supplies, evaluation modules, instruments, meters, scopes and other
related apparatus used in a development environment exceeding 50Vrms/75VDC must be
electrically located within a protected Emergency Power Off EPO protected power strip.
(e) Use stable and nonconductive work surface.
(f) Use adequately insulated clamps and wires to attach measurement probes and instruments. No
freehand testing whenever possible.
2. Electrical Safety
As a precautionary measure, it is always a good engineering practice to assume that the entire EVM
may have fully accessible and active high voltages.
(a) De-energize the TI HV EVM and all its inputs, outputs and electrical loads before performing any
electrical or other diagnostic measurements. Revalidate that TI HV EVM power has been safely de-
energized.
(b) With the EVM confirmed de-energized, proceed with required electrical circuit configurations,
wiring, measurement equipment connection, and other application needs, while still assuming the
EVM circuit and measuring instruments are electrically live.
(c) After EVM readiness is complete, energize the EVM as intended.
WARNING: WHILE THE EVM IS ENERGIZED, NEVER TOUCH THE EVM OR ITS ELECTRICAL
CIRCUITS AS THEY COULD BE AT HIGH VOLTAGES CAPABLE OF CAUSING ELECTRICAL
SHOCK HAZARD.
3. Personal Safety
(a) Wear personal protective equipment (for example, latex gloves or safety glasses with side shields)
or protect EVM in an adequate lucent plastic box with interlocks to protect from accidental touch.
Limitation for safe use:
EVMs are not to be used as all or part of a production unit.
All trademarks are the property of their respective owners.

Chapter 1
SLAU587–August 2014
Getting Started
1.1 Preface
Thank you for selecting Texas Instruments EVM430-i2040SUBMTR development tool. This development
tool provides you the resources to evaluate the performance of MSP430i2040 utilizing as embedded
metering application. This documentation will guide you to get familiar with this development tool and will
provide necessary information to start further development and evaluation. Before proceeding, read this
guide to gain basic understanding and knowledge of this development tool and how to safely operate it.
More resources related to this development tool are available for download from the Texas Instruments
web site, including more documentation, application notes, example application code, and software.
1.2 Safety and Precautions
The EVM is designed to operate by professionals who received appropriate technical training yet it is
designed to operate from ac supply or high voltage dc supply please read the safety related documents
that come with the EVM package and this user guide before operating this EVM.
CAUTION
Read user guide before use.
CAUTION
Do not leave EVM powered when unattended.
WARNING
HOT SURFACE : Contact may cause burns, do not touch.
WARNING
DANGER HIGH VOLTAGE : Electric shock possible when
connecting board to live wires. Board should be handled with care
by professional. For safety, use of isolated equipment with
overvoltage and overcurrent protection is highly recommended.

www.ti.com Package Contents
1.3 Package Contents
• Quick start guide
• Safety guideline
• Terms and disclaimer
• Disc containing software and user guide
• EVM430-i2040SUBMTR
1.4 Introduction
The Texas instruments MSP430i2040 is an ultra-low-power mixed-signal microcontroller. It integrates four
independent differential-input 24-bit sigma-delta analog-to-digital converters with programmable gain
amplifiers, a 16-bit hardware multiplier, an eUSCI_A0 that supports UART and SPI communication
interfaces, an eUSCI_B0 that supports SPI and I2C communication interfaces, two 16-bit timers, and 12
GPIO pins in a 28-pin TSSOP or 16 GPIO pins in a 32-pin QFN package. The peripheral set is a good
combination for electricity power measurement.
This EVM is designed as an evaluation tool for using the MSP430i2040 in the application of embedded
metering (sub-metering). In this application, the electricity measuring device is embedded in the end
application and provides the user with information about the voltage, current, and power consumption of
the device. Moreover, the EVM can compensate for the line resistance and EMI filter capacitance.
Embedded metering (sub-metering) is applicable in many areas such as:
• Home appliances
• Server or PC power supplies
• UPS
• Smart plugs or power strips
• Solar energy inverter
• Electrical vehicle charger
• Home monitoring, security, and automation
In this document, all the description of the configuration, operation, features, behaviors, functions, and
interfaces is based on the default firmware that is pre-programmed on the EVM and the original EVM
hardware design. Proper functionality is not ensured if changes made to the hardware or the firmware.
1.5 Features
Hardware features
• Spy-Bi-Wire debugging interface
• 14-pin debugger connector allows direct interface to MSP-FET430UIF without the need of an adaptor
• Built-in switching-mode power supply capable of supply from 85 to 265 VAC (47 Hz to 63 Hz) or 120 to
380 VDC simplifies evaluation setup
• Built-in RS232 external communication interface for reading measurements and performing calibration
• Seven built-in LEDs for customer debugging and visual monitoring
Software features
• Measurement of root mean square (rms) voltage, rms current, active power, reactive power, apparent
power, power factor, ac frequency, voltage THD, current THD, fundamental voltage, fundamental
current and fundamental active power
• Readings update every four ac cycles or 80 ms in case of dc input
• Capable of ac and dc measurement
• Capable of switching between ac and dc measurement mode automatically
• Capable of EMI filter capacitor and wire resistance compensation
• No separate dc calibration required
7
SLAU587–August 2014 Getting Started
Submit Documentation Feedback Copyright © 2014, Texas Instruments Incorporated

Isolator circuit
Shunt Sensor
Voltage Sensor
Power Supply Fuse
Built-in
Power Supply
JTAG/UART Options
I2C, CLK IN
Built-in/External
Supply Option
VDD
VSS
Isolated Serial
Communication (Not Isolated)
Debug Interface
Hardware www.ti.com
1.6 Hardware
This section introduces the parts on the EVM and describes the procedures to set up the hardware for
evaluation.
1.6.1 Top View of the EVM
Figure 1-1. EVM Top View
1.6.2 Bottom View of the EVM
Figure 1-2. EVM Bottom View
8Getting Started SLAU587–August 2014
Submit Documentation Feedback
Copyright © 2014, Texas Instruments Incorporated

www.ti.com Hardware
1.6.3 Hardware Setup Procedures
1.6.3.1 Power Supply to EVM
The design of the EVM allows power to the EVM be supplied from the built-in power supply, which takes
the line input to generate the power needed by the EVM. The EVM also allows power to the EVM be
supplied from user source.
The EVM is shipped with the built-in power supply block installed. If power is to be supplied from external
power supply, disconnect the built-in VSK-S1-3P3U power supply block. Remove the two jumpers on J5,
and apply 3.3 V to VDD and VSS on J5 as shown in Figure 1-1.
CAUTION
Do not supply power to the EVM until the hardware and software setup is
completed.
1.6.3.2 Serial Communication Interface
Connect an RS232 extension cable to the DB-9 connector on the EVM and to a standard RS232 port on a
computer.
1.6.3.3 Line Input and Load Output
•Solder the ac source live or dc source positive to LIVE_IN connector.
•Solder the ac source neutral or dc source negative to NEUTRAL_IN connector.
•Solder the load's live or positive power input to LIVE_OUT connector.
•Solder the load's neutral or negative power input to NEUTRAL_OUT connector.
1.6.3.4 Debugging Interface
Spy-Bi-Wire is used on this EVM as the debug interface to external debugger.
Before connecting to MSP-FET430UIF, if the power (while debugging) to the i2040 device is to be
supplied by the FET then short pins 1 and 2 of J8 (toward board edge). If the power (while debugging) to
the i2040 device is to be supplied by voltage on VDD pin, then short pins 2 and 3 of J8 (toward board
center) (see Figure 1-1).
CAUTION
The debugging interface is NOT ISOLATED; make sure that proper isolation is
in place between the EVM and the PC using for debugging.
NOTE: Connection to debugging interface is optional for the operation of the EVM. The EVM can
operate standalone without debugger connected.
9
SLAU587–August 2014 Getting Started
Submit Documentation Feedback Copyright © 2014, Texas Instruments Incorporated

Calibrator Software www.ti.com
1.7 Calibrator Software
A package of software is needed to access full functionality of the EVM. The EVM package comes with
the firmware pre-programmed into i2040 that allows the EVM to operate properly. The EVM also has a
software package that is on the disc that comes with the EVM or the user can download the package from
Texas Instruments web site. This section discusses the software in the software package and the
procedure to setup the software to operate with the EVM
1.7.1 Software Package Content
The ZIP file for the EVM consist of several packages includes :
• PC Software tool to run on PC for reading and calibrating the EVM. The setup and operation of this PC
software tool is described in Section 1.7.2 and in Chapter 3.
• Source code and Embedded Metering Library. This will be discussed in Chapter 5 and Appendix A.
• Hardware design files including schematic, layout and bill of materials (also see Appendix B).
1.7.2 Setting up the PC Software Tool
1.7.2.1 Minimum System Requirement
• PC with RS232 port or a RS232 port through USB
• PC running Microsoft Windows XP SP3 or Windows 7
The software tool has been tested to run properly on a Pentium M 1.4-GHz PC with 1.25GB of RAM
installed; thus, it is assumed that most of the computers today meet the processing power requirement.
1.7.2.2 Installing the Software
Extract the file named calibrator-runtime.zip into any folder. A folder named calibrator-runtime that
contains the necessary files to run the software tool is created. The file named calibrator-20121120.exe is
the executable file of the software tool. The file named calibrator-config.xml contains the setup information
for the software tool. Edit this XML file before calibrator-20121120.exe is launched (see Section 1.7.2.3).
10 Getting Started SLAU587–August 2014
Submit Documentation Feedback
Copyright © 2014, Texas Instruments Incorporated

www.ti.com Calibrator Software
1.7.2.3 Configuring the Software
Follow these steps to edit the XML for calibrator-20121120.exe to run properly.
1. Right click My Computer Icon and select Properties in the pop-up menu.
2. Select the Hardware tab in the System Properties Window, then Click the Device Manager to go to
the Device Manager window.
Figure 1-3. System Properties Window
11
SLAU587–August 2014 Getting Started
Submit Documentation Feedback Copyright © 2014, Texas Instruments Incorporated

Calibrator Software www.ti.com
3. Find the COM port number of the serial port that connecting the PC and the EVM.
Figure 1-4. Device Manager Window
12 Getting Started SLAU587–August 2014
Submit Documentation Feedback
Copyright © 2014, Texas Instruments Incorporated

www.ti.com Instruments
4. Open calibration-config.xml in the folder calibrator-runtime with a text editor or XML editor. Go to the
line as shown below, enter the COM port number, and save the file.
Figure 1-5. Edit calibration-config.xml
1.8 Instruments
The EVM has been programmed with a set of calibration factors that give readings accurate to within a
few percent. If more accurate results are needed, the EVM must be calibrated (see Chapter 3). The
following instruments are suggested to perform calibration:
• An ac source that can output sufficient power to drive the load at rated frequency (for example, 50 to
60 Hz) and rated voltage (for example, 110 to 220 V) or an ac test set that can generate the rated
frequency and voltage.
• A variable ac load or the UUT. If DC measurement is needed, a variable dc load or the UUT is also
recommended. Alternatively an ac test set that can generate the rated loading.
• A reference meter that can give ac parameters of V_RMS, I_RMS, and P_ACTIVE.
The following links provide information about the instruments that were used for testing and calibrating the
design.
• AC Meter Test Set: http://en.3gcnkaipu.com/products_list/&pmcId=10.html
• Reference Meter:
http://www.hc.com.tw/portal_c1_cnt_page.php?owner_num=c1_142363&button_num=c1&folder_id=17
560&cnt_id=124863&search_field=&search_word=&search_field2=&search_word2=&search_field3=&s
earch_word3=&bool1=&bool2=&search_type=1&up_page=1
• AC Source: http://www.chromausa.com/acpowersources/61500lo-ac-source.php
• Reference Meter: http://www.chromausa.com/powermeters/66201-66202-digital-power-meters.php
• DC Electronic Load: http://www.chromausa.com/dcloads.php#6310a
13
SLAU587–August 2014 Getting Started
Submit Documentation Feedback Copyright © 2014, Texas Instruments Incorporated

Chapter 2
SLAU587–August 2014
Operating the PC Software Tool
2.1 Introduction
This section describes the operation of the EVM and the PC software tool. Before proceeding, make sure
that the steps described in Chapter 1 are completed, power is applied to the EVM, and line voltage to the
load is applied.
2.2 Start Using the EVM
When the EVM has been powered, some of the seven LEDs flash or turn on to indicate its operation
status. Some of the LED are not used, and you can make change to the provided source code to make
use of all of the seven LEDs as needed in the application. Table 2-1 shows the pre-programmed meaning
of the LEDs.
Table 2-1. LED Indicators
LED State Indication
ON Background operations running
LED1 OFF Background operations completed
ON Negative voltage half cycle
LED2 OFF Positive voltage half cycle
ON Not used
LED3 OFF Not used
ON Foreground operations running
LED4 OFF Foreground operations completed
ON EVM is in ac mode measurement
LED5 OFF EVM is not in ac mode measurement
ON EVM is in dc mode measurement
LED6 OFF EVM is not in dc mode measurement
ON Active energy pulse pulsing
LED7 OFF Active energy pulse idle
The EVM is now ready to run, so launch the software calibrator-20121120.exe in the folder calibration-
runtime to start communicating with the EVM. A window as shown in Figure 2-1 appears. As defined in the
XML file calibration-config.xml, meter position 1 is assigned the serial port to communicate with the EVM.
The Comms indicator turns green if communication to EVM from PC is established, and it flashes
between read and green when communication is taking place.
14 Operating the PC Software Tool SLAU587–August 2014
Submit Documentation Feedback
Copyright © 2014, Texas Instruments Incorporated

www.ti.com Start Using the EVM
Figure 2-1. Calibrator Software Startup Window
Click the Comms indicator to open the Meter Status window (see Figure 2-2).
15
SLAU587–August 2014 Operating the PC Software Tool
Submit Documentation Feedback Copyright © 2014, Texas Instruments Incorporated

Start Using the EVM www.ti.com
Figure 2-2. Meter Status Window
This window shows the current reading of the meter. The background of a text box is gray if the EVM
does not support that particular reading. The background turns red if the reading from EVM to that box
has a large variance. The background turns yellow if the reading from EVM has a fairly low variance. The
background turns green if the reading has a low variance. Note that the software on PC reads the EVM
every second and also averages the data read; thus, the update rate is slower than the update rate of the
EVM.
At the bottom of this window, there are four buttons.
• Click the Meter Consumption button to open the Meter Consumption window. Because the EVM
does not support this feature, the Meter Consumption window gives no useful information.
• Click the Meter Calibration Factors button to open the [Meter Calibration Factors] window (see
Figure 2-3). This window shows the current calibration factor values.
16 Operating the PC Software Tool SLAU587–August 2014
Submit Documentation Feedback
Copyright © 2014, Texas Instruments Incorporated

www.ti.com Start Using the EVM
Figure 2-3. Meter Calibration Factor Window
• Click the Meter Features button to open the Meter Features window (see Figure 2-4). This window
shows the supported features of the EVM. Note that Figure 2-4 shows only the look and feel of the
meter feature window, but this is not the exact feature of the EVM.
Figure 2-4. Meter Features Window
• Click the Manual Cal button brings up the Meter Error window. In this window, the adjustment to the
calibration factor values could be done by entering the percentage error of the reading from the EVM
compare to the reading from the reference meter. The technique and procedure of performing
17
SLAU587–August 2014 Operating the PC Software Tool
Submit Documentation Feedback Copyright © 2014, Texas Instruments Incorporated

% 100
EVM Reading Reference Meter Reading
Error %
Reference Meter Reading

u
Known Issues www.ti.com
calibration is discussed in Chapter 3.
Figure 2-5. Meter Error Window
To modify the calibration factor requires the correction to be entered in the percentage error. The
percentage error is calculated as shown in Equation 1.
(1)
Type the percentage error in the corresponding box in Meter Calibration window. Click Update meter,
and the updated calibration values are calculated and written to the EVM. The corresponding values are
shown in the Meter Calibration Factor window.
2.3 Known Issues
The calibrator software is legacy software that operates with utility meters and has not been customized
completely for embedded metering. The following list are the known issues with the existing software.
These issues are scheduled to be fixed in the next version of calibrator software that is customized for
embedded metering.
• Neutral Monitoring is shown in the Meters Features window as a supported feature, but this is not
correct. When wire resistance compensation or inlet capacitor compensation is enabled, the calibrator
interprets this as neutral monitoring support.
• Resistance value of wire resistance compensation and capacitance value of inlet capacitor
compensation cannot be programmed with calibrator software.
• Voltage ac offset value cannot be written with the calibrator software. The value that is entered in the
Voltage AC offset field is written to the Current AC offset, instead. The value that is entered in the
Current AC offset box has no effect.
• DC Offset values cannot be written to the EVM with the calibration software. The current firmware
takes the current and voltage dc offset value every time any calibration value is updated.
• Aggregate current in the [Meter Status] window always shows 10.0000 A.
18 Operating the PC Software Tool SLAU587–August 2014
Submit Documentation Feedback
Copyright © 2014, Texas Instruments Incorporated

Chapter 3
SLAU587–August 2014
Calibration Techniques
3.1 Introduction
The EVM is programmed with statistical calibration values that allow the EVM to measure and give
roughly accurate readings; however the EVM has not been calibrated while shipped. To maximize
accuracy and to compensate component and manufacturing tolerance it is necessary for the EVM to go
through a calibration process. In this chapter the calibration techniques, required instruments, procedure
and steps of calibration will be discussed.
3.2 Calibration Techniques
The calibration of the EVM is defined based on the front-end interface model as shown in Figure 3-1.
Figure 3-1. Front-End Interface Model
For the current design a 2 point calibration and characterization is required. VGAIN, IGAIN, PGAIN, CAP,
RES, VDC_OFFSET, IDC_OFFSET are parameters that will be calibrated during the process; an
estimated value is put into the memory during design/characterization to help to speed up calibration.
(Note : Default CAP and RES should set to 0 before calibration).
VAC_OFFSET, IAC_OFFSET, PHASE_CORRECT are parameters that may not need calibration but a
characterization would be sufficient for embedded metering application except for high accuracy of <
0.1%.
NOTE: The calibration values are written in one flash page in the EVM. Therefore, when a new
value needs to be written, the whole page is erased. The provided GUI performs the read,
modify, and write operation automatically. If a custom calibration method is implemented, the
application must read the complete set of calibration values, update the modified fields, and
write the complete set back to the EVM.
19
SLAU587–August 2014 Calibration Techniques
Submit Documentation Feedback Copyright © 2014, Texas Instruments Incorporated

% 100
UUT REF
REF
I I
Error %
I

u
1REF n n
UUT
I
IGAIN IGAIN
I
u
% 100
UUT REF
REF
V V
Error %
V

u
1REF n n
UUT
V
VGAIN VGAIN
V
u
Calibration Procedures www.ti.com
3.3 Calibration Procedures
3.3.1 Calibration of AC and DC Parameters
To calibrate the ac and dc parameters:
1. Calibrating VGAIN
(a) Set to No / Lowest possible load.
(b) Set VIN to line voltage.
(c) Calculate the value for VGAIN with Equation 2.
where
• VGAINn+1 is the new voltage calibration factor
• VGAINnis the original voltage calibration factor
• VREF is the reference meter voltage reading at the voltage set for VGAIN calibration
• VUUT is the unit under test voltage reading at the voltage set for VGAIN calibration (2)
Or if percentage error is used (as with the provided calibration software):
(3)
(d) Write and apply the calibrated VGAIN.
2. Calibrating IGAIN
(a) Set VIN to line voltage.
(b) Set to High / Highest possible load.
(c) Calculate IGAIN value with Equation 4.
where
• IGAINn+1 is the new current calibration factor
• IGAINnis the original current calibration factor
• IREF is the reference meter current reading at the current set for IGAIN calibration
• IUUT is the unit under test current reading at the current set for IGAIN calibration (4)
Or if percentage error is used (as with the provided calibration software):
(5)
(d) Write and apply the calibrated IGAIN.
20 Calibration Techniques SLAU587–August 2014
Submit Documentation Feedback
Copyright © 2014, Texas Instruments Incorporated