nrf5x OTA Testing with LitePoint Bluetooth Advanced nwp_028

Transcription

1 nrf5x OTA Testing with LitePoint Bluetooth Advanced nwp_028 White Paper v1.0 /

2 Contents 1 Revision history iii Introduction Minimum requirements LitePoint Bluetooth Advanced measurement methodology Test coverage Test recommendations BLE_SMART_TX_ONLY test BLE_SMART_TX_RX_PER test BLE_SMART_TX_RX_SWEEP test BLE_SMART_DIRTY_SWEEP_CAL test I/O parameters Setting up LitePoint Bluetooth Advanced solution Setting up LitePoint IQxel-M tester Installing nrf5 SDK Extracting ble_app_hrs_litepoint example Installing nrf5x Command Line Tools Installing LitePoint IQfact+ software Performing LitePoint Bluetooth Advanced test Troubleshooting Legal notices ii

3 Revision history Date Version Description January First release iii

4 1 Introduction This white paper describes how the LitePoint Bluetooth Advanced solution can be used to perform overthe-air (OTA) production testing of nrf5x devices. The main function of a production test is to verify that all the components are mounted correctly and have the correct values after assembling a device. A production test on an nrf5x Bluetooth Low Energy device can be performed using the LitePoint Bluetooth Advanced solution. This test solution is able to characterize and verify Bluetooth Low Energy devices through over-the-air testing. Because the end product can be tested fully assembled, product developers can get their products on the market quickly knowing they are reliable and will perform as expected, including the antenna. Figure 1: LitePoint Bluetooth Advanced solution 1.1 Minimum requirements Before you start, check that you have the required hardware and software. Hardware requirements Intel i3 processor (or equivalent) 2 GB RAM (4 GB recommended) 2 GB HDD space nrf52 Development Kit (DK) LitePoint IQxel-M RF enclosure RF coax Software requirements Windows XP/7 nrf5 Software Development Kit (SDK) v or later nrf5x Command Line Tools LitePoint Bluetooth Measurement and LitePoint Bluetooth Advanced licenses installed in LitePoint IQxel-M LitePoint IQfact+ software installed on a computer 4

5 2 LitePoint Bluetooth Advanced measurement methodology nrf5x devices use dedicated advertising channels to transmit beacon signals or to establish a connection with a controller. These advertising channels are distributed across the 2.4 GHz band, providing a method to characterize a device at multiple frequencies. The LitePoint IQxel-M with LitePoint Bluetooth Advanced measurement solution uses these advertising channels to perform transmitter power, transmitter quality, and receiver sensitivity measurements, providing excellent coverage and confidence in the parametric performance of the device. The nrf5x device is tested with commercial firmware, not test firmware, so that the results correlate with actual performance of real devices. The results generated for the three advertising channels with the OTA method correlate with the traditional Direct Test Mode (DTM) approach. 2.1 Test coverage The LitePoint Bluetooth Advanced solution allows you to test the following parameters. Transmitter tests: Power (Min, Max, Average) Delta F1 Delta F2 Minimum Deviation Frequency Drift Frequency Offset Adjacent Channel Power Advertising Packet Period Receiver tests: Packet Error Rate Sensitivity 2.2 Test recommendations The LitePoint Bluetooth Advanced solution provides four preconfigured tests, where each test is intended for a specific purpose. 5

6 LitePoint Bluetooth Advanced measurement methodology LitePoint Bluetooth Advanced test Recommended usage name BLE_SMART_TX_ONLY Manufacturing or design verification. This test is used for beacon devices which do not have the receiver enabled. It can be used as a quick test on any device to ensure it is operational (transmitting). BLE_SMART_TX_RX_PER Manufacturing. This test is used for peripheral devices which have both the transmitter and receiver enabled. It can be configured to be very fast, and it provides both TX and RX results in a few seconds. BLE_SMART_TX_RX_SWEEP Fixture calibration or design verification. This test is used for Peripheral devices which have both TX and RX enabled. It provides TX results and RX sweep to determine 50% PER (packet error rate) point. BLE_SMART_DIRTY_SWEEP_CAL RX correlation or design verification. This test is used for Peripheral devices which have both TX and RX enabled. It provides TX results and RX sweep to determine Bluetooth Special Interest Group (SIG) recommended 0.1% BER (bit error rate) point. Table 1: Test recommendations BLE_SMART_TX_ONLY test This test is used primarily for transmit-only Bluetooth Beacon devices. Normally only one test (BLE_SMART_TX_ONLY) is included in the test flow. It can also be useful as a quick test before performing a longer measurement, such as BLE_SMART_RX_Sweep. This test performs TX measurements on all advertising channels (37, 38, and 39). A typical test time is 2-3 seconds for a device with a 100 msec advertising period BLE_SMART_TX_RX_PER test This test is used for Bluetooth Smart Peripheral devices to quickly verify both the transmitter and receiver RF performance in a manufacturing environment. TX and RX tests are performed in parallel, so there is no time penalty to perform receiver testing. This test (BLE_SMART_TX_RX_PER) provides both the TX and RX results. Therefore, the test flow will normally only contain this one item. In this test, the user specifies the number of packets, TX and RX path loss, and the power level to test the receiver sensitivity. This test is intended to be used in manufacturing with a small number of packets as a rapid check of the TX and RX performance. The RX Power Level is normally set to a fairly high value, approximately 10 db above the actual expected sensitivity. If the receiver is working, you should get near 0% PER. If the receiver is not working properly, you will likely get 100% PER. A typical test time is 2-3 seconds for a device with a 100 msec advertising period BLE_SMART_TX_RX_SWEEP test This test is a fast method for measuring receiver sensitivity. It is intended to be used in engineering evaluation, not manufacturing. This method provides a fast and reliable measurement to determine the 50% PER point of a device which can be easily correlated with the Bluetooth SIG 0.1% BER (see BLE_SMART_DIRTY_SWEEP_CAL test on page 7). The BLE_SMART_TX_RX_SWEEP test provides both the TX and RX results. This test uses a proprietary LitePoint algorithm and sweeps the RF output level of the tester. It requires approximately 200 advertising intervals to converge to the 50% PER point. Therefore, this test will take 6

7 LitePoint Bluetooth Advanced measurement methodology approximately 20 seconds on a device with a 100 ms advertising period. In the characterization of the nrf52832, LitePoint found the 50% PER point to be offset by approximately 2 db from the 0.1% BER point (corresponds to a 30.8% PER) specified by the Bluetooth SIG. To determine the actual offset, the LitePoint solution provides BLE_SMART_DIRTY_ SWEEP_CAL test to determine the RX sensitivity using the Bluetooth SIG method BLE_SMART_DIRTY_SWEEP_CAL test This test performs true RX sensitivity based on the Bluetooth SIG defined parameters. The key elements of this test are Dirty Packets, 1500 packets per level, and 0.1% Bit-Error-Rate as defined by Bluetooth SIG. This test can be a very long test that requires minutes or even hours depending on the device under test (DUT) advertising interval. It is therefore intended only for design verification. This test is used for pre-conformance or to create offset correction values, which is the difference in db between the 0.1% BER, which takes a long time to find, and the 50% PER point, which can be found very quickly. This test only needs to be run once since the offset differences between 50% PER and 0.1% BER are chipset dependent, not device dependent. Once you know these values for your chipset (roughly 1.9 to 2.1 db on nrf52832), you can use the faster BLE_SMART_TX_RX_SWEEP test to find the 50% point and add this offset number to get true Bluetooth SIG receiver sensitivity. 2.3 I/O parameters Each of the four pre-configured tests specify input and output parameters. An input parameter consists of a parameter name, its unit, type, and value. An output parameter, also referred to as a return value, consists of parameter type, value, and upper and lower limits. The test limits for a single measurement can be specified by using the upper limit and the lower limit columns. The input and output parameters for the preconfigured tests are described in the following tables. 7

8 LitePoint Bluetooth Advanced measurement methodology Test name I/O Type Description BLE_SMART_TX_ONLY INPUT PACKET_NUMBER The number of packets that will be measured on each channel. Results are averaged across the number of measured packets. OUTPUT ACP_POWER_DBM_OFFSET Adjacent Channel Power ADV_PACKET_PERIOD The interval between sets of advertising packets DELTA_F1_AVG Estimated FM Deviation for pattern DELTA_F2_AVG Estimated FM Deviation for pattern FREQ_DRIFT Maximum measured frequency drift within the packet FREQ_OFFSET Carrier frequency offset of the transmitted signal MIN_DEV Minimum deviation from center frequency for any 1 or 0 in the data packet POWER_AVG Average power from each packet, averaged across all packets measured. POWER_MAX Maximum power from each packet, averaged across all packets measured. POWER_MIN Minimum power from each packet, averaged across all packets measured. DUT_BD_ADDRESS DUT advertising address Table 2: I/O parameters for BLE_SMART_TX_ONLY 8

9 LitePoint Bluetooth Advanced measurement methodology Test name I/O Type Description BLE_SMART_TX_RX_PER INPUT PACKET_NUMBER The number of packets that will be measured on each channel. Results are averaged across the number of measured packets. POWER LEVEL This is the RF power level that will be used for RX PER testing. The actual power level from the tester will be POWER_LEVEL + PATH_LOSS. ACK_COUNT The number of packets successfully received by the DUT DELTA_F1_AVG Estimated FM Deviation for pattern DELTA_F2_AVG Estimated FM Deviation for pattern FREQ_DRIFT Maximum measured frequency drift within the packet FREQ_OFFSET Carrier frequency offset of the transmitted signal MIN_DEV Minimum deviation from center frequency for any 1 or 0 in the data packet PER Calculated PER = (TOTAL_VALID_PACKET ACK_COUNT)/TOTAL_VALID_PACKET POWER_AVG Average power from each packet, averaged across all packets measured. POWER_MAX Maximum power from each packet, averaged across all packets measured. POWER_MIN Minimum power from each packet, averaged across all packets measured. VALID_TOTAL_PACKET Number of packets sent on each channel. Because of the algorithm used, this can be slightly different from the PACKET_NUMBER defined in the input. DUT_BD_ADDRESS DUT advertising address OUTPUT Table 3: I/O parameters for BLE_SMART_TX_RX_PER 9

10 LitePoint Bluetooth Advanced measurement methodology Test name I/O BLE_SMART_TX_RX_SWEEP INPUT OUTPUT Type Description MODE If 0, then the RX sensitivity values are used and the path losses are measured (with the assumption that TX and RX path losses will be identical). If 1, then the user-defined path losses are used and RX sensitivity is measured. PACKET_NUMBER Sets the maximum number of packets that will be used to search for RX sensitivity SENSITIVITY The receiver sensitivity (if known). Used with Mode=0 to measure path losses DELTA_F1_AVG Estimated FM Deviation for pattern DELTA_F2_AVG Estimated FM Deviation for pattern FREQ_DRIFT Maximum measured frequency drift within the packet FREQ_OFFSET Carrier frequency offset of the transmitted signal MIN_DEV Minimum deviation from center frequency for any 1 or 0 in the data packet PATH_LOSS_DB These values are measured with Mode=0. The path loss values are calculated based on measurement of the known receiver 50% PER point. POWER_AVG Average power from each packet, averaged across all packets measured. POWER_MAX Maximum power from each packet, averaged across all packets measured. POWER_MIN Minimum power from each packet, averaged across all packets measured. RX_FAST_SENSITIVITY Measured RX sensitivity (50% PER point) on each channel DUT_BD_ADDRESS DUT advertising address Table 4: I/O parameters for BLE_SMART_TX_RX_SWEEP 10

11 LitePoint Bluetooth Advanced measurement methodology Test name I/O BLE_SMART_DIRTY_SWEEP_CAL INPUT OUTPUT Type Description MAXIMUM_RETRY The sweep algorithm expects the DUT PER to decrease to near 0 with increasing RF level. When using dirty packets, some DUTs struggle to get low PER even with high signal level. This retry mechanism allows algorithm to retry multiple times before failing. PER_0_100_RANGE_DB The typical DUT has 5-10 db range from 0 to 100% PER. If this range is known, setting this value will help the algorithm converge more quickly. 5 db is a good starting point for most DUTs. Increase to 10 db if sweep fails to converge. DELTA_DB This is the difference, in db, between the Bluetooth SIG 0.1% BER and the 50% PER point. Dirty_SWEEP_SENSITIVITY_DBM This is receiver sensitivity as defined by the Bluetooth SIG test standard. Table 5: I/O parameters for BLE_SMART_DIRTY_SWEEP_CAL 11

12 3 Setting up LitePoint Bluetooth Advanced solution This section will guide you through the installation and setup of the required software as well as the setup of the hardware. 3.1 Setting up LitePoint IQxel-M tester This section will guide you through connecting the LitePoint IQxel-M tester to power and Ethernet and finding the IP address of the LitePoint IQxel-M tester. Complete the following steps to set up the IQxel-M tester: 1. On the back panel of the LitePoint IQxel-M tester, connect the power cable, an Ethernet cable, and a VGA cable to a monitor. 2. On the front panel of the LitePoint IQxel-M tester, connect one end of the RF coax to the RF1 connector and the other end to the RF enclosure. 3. To power up the LitePoint IQxel-M tester, press the power button on the front panel. The monitor connected to the LitePoint IQxel-M tester now displays the LitePoint Monitor: 12

13 Setting up LitePoint Bluetooth Advanced solution 4. Take note of the IP address as you will need it in Performing LitePoint Bluetooth Advanced test on page Installing nrf5 SDK To perform a LitePoint Bluetooth Advanced test, the nrf5 SDK needs to be installed. Complete the following steps to install the nrf5 SDK: 1. Download the nrf5_sdk_14.2.0_17b948a.zip repository file from developer.nordicsemi.com. 2. Extract the.zip file to the directory that you want to use to work with the SDK. 3. To install the nrf5 MDK, open an example project. Keil will prompt you to install the nrf_devicefamilypack. If Keil does not prompt you, open the Pack Installer, click Check For Updates, and install the latest nrf_devicefamilypack. 3.3 Extracting ble_app_hrs_litepoint example Attached to this white paper is a modified version of the nrf5 SDK v Heart Rate Application, ble_app_hrs_litepoint, which advertises indefinitely and uses an advertising interval of 100 ms. The unaltered Heart Rate Application example in the nrf5 SDK v will stop advertising after 180 seconds and uses an advertising interval of 300 ms, making it unsuitable for time-consuming tests and increasing the time it takes to run tests. Extract the attached ble_app_hrs_litepoint.zip into the nrf5_sdk_14.2.0_17b948a \examples\ble_peripheral folder. The example has been precompiled and merged with the S132 v This precompiled binary is located in the ble_app_hrs_litepoint\hex folder. 3.4 Installing nrf5x Command Line Tools Before performing a LitePoint Bluetooth Advanced test, the nrf5x Command Line Tools need to be installed. When installing on Windows, the SEGGER software is automatically installed with the nrf5x Command Line Tools. Complete the following steps to install the nrf5x Command Line Tools: 1. Download the software for Windows from nrf5x-command-line-tools for Win Run the installer and follow the given instructions. 13

14 Setting up LitePoint Bluetooth Advanced solution After running the installer, the nrf5x Command Line Tools are ready for use. 3.5 Installing LitePoint IQfact+ software To perform a LitePoint Bluetooth Advanced test, the LitePoint IQfact+ software needs to be installed. To obtain the LitePoint Bluetooth Advanced solution, contact a LitePoint sales representative or visit litepoint.com. Complete the following steps to install the LitePoint IQfact+ software: 1. Extract the contents of the IQfact+_BLE_Smart_ zip file to a folder. 2. Open the IQfact_plus folder, and double-click Setup.exe to begin the installation. 3. In the IQfact+_BLE_Smart Setup Wizard window, click Next. 4. In the License Agreement window, click I Agree. 5. In the IQfact_plus installation window, select all programs that have not been previously installed on the computer. Then click Install Selected Items. 6. In the Choose Components window, select all components, and click Next. 7. Click Finish to complete the installation process and close the wizard. 14

15 4 Performing LitePoint Bluetooth Advanced test This section will guide you through the test procedure with the attached ble_app_hrs_litepoint example running on the nrf52 DK. Complete the following steps to perform a LitePoint Bluetooth Advanced test: 1. Connect the LitePoint IQxel-M tester to the computer. 2. To start IQFactStudio, select it in the Windows Start Menu. 3. Click the IQfact+ icon. 4. In File, click Open, and select ble_smart_test. 5. In the left pane, select 1.CONNECT_IQ_TESTER. 6. In the middle pane, enter the IP address of the LitePoint IQxel-M tester in the Value field of IQTESTER_MODULE_01. You can find the IP address of the LitePoint IQxel-M tester by attaching a monitor to the tester. 7. In BLE_SMART_GLOBAL_SETTINGS, which is the next item in the left pane, make sure that the RF1A RF port is selected. Leave the other values with their default value. BLE_SMART_GLOBAL_SETTINGS defines the global settings that will be used for all subsequent tests that are run, for example, path loss, output power, and which RF port is used. 15

16 Performing LitePoint Bluetooth Advanced test 8. To set the run mode of each individual test, right-click the selected test, select Run Mode, and set the applicable run mode. As only BLE_SMART_TX_RX_PER must be run, select all the other tests and set their Run Mode to Skip. 9. Set the packet number to 10 and the power level to -30dbm. 10.To save the test flow, in File, click Save As, and give the test flow a unique name, such as My_nRF52_TX_test. 11.Flash the nrf52 DUT with the precompiled firmware ble_app_hrs_litepoint_pca10040_s132.hex that is located in the nrf5_sdk_14.2.0_17b948a\examples\ble_peripheral\ble_app_hrs_litepoint 16

17 Performing LitePoint Bluetooth Advanced test \hex folder if you extracted the ble_app_hrs_litepoint example as described in Extracting ble_app_hrs_litepoint example on page 13. Use the following nrfjprog command: nrfjprog --family nrf52 --program ble_app_hrs_litepoint_pca10040_s132.hex --chiperase -reset This will erase the flash of the nrf52832, flash the.hex file, and reset the nrf On the nrf52 DK, LED1 will start blinking, indicating that it is advertising. 12.Remove the USB cable connecting the nrf52 DK to your computer. 13.Insert a CR2032 coin cell battery into the battery holder of the nrf52 DK. 14.Power on the nrf52 DK and verify that the nrf52832 is advertising (LED1 is blinking). 15.Place the nrf52 DK in the RF enclosure and close the lid. 16.To run a test in IQfactStudio, go to Tools and select IQfactRun_Console, or click the blue arrow. This will run the test flow. 17.Review the measurement results. They are shown in a DOS window but also automatically saved as a log and.csv file. 17

18 5 Troubleshooting These troubleshooting instructions can help you fix issues you may encounter when performing a LitePoint Bluetooth Advanced test. How can I speed up my testing? Test time is directly dependent on advertising interval. To reduce test time, set nrf52 to have a shorter advertising period. Measurements are not triggering. What is the likely cause? The tester needs approximately -35 dbm at the front panel connector. Try repositioning nrf52 in the RF enclosure closer to the RF coupler. I want to use a newer version of the nrf5 SDK. What changes do I have to do in the ble_app_hrs example code? The ble_app_hrs example from a newer SDK version can be used as is, but it will only advertise for 180 s and has a default advertisement interval of 300 ms. To run longer tests and reduce the duration of the test, the ble_app_hrs example needs to be modified so that it advertises indefinitely and uses a 100 ms advertisement interval. This is done by altering the values of the APP_ADV_INTERVAL and APP_ADV_TIMEOUT_IN_SECONDS defines in the main.c file of the example: #define APP_ADV_INTERVAL 100 #define APP_ADV_TIMEOUT_IN_SECONDS 0 18

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