nAN-34 Production test using DTM.fm

nAN-34 Production test using DTM.fm
Setting up production test using DTM
nAN-034
Application Note v1.0
Copyright © 2013 Nordic Semiconductor ASA. All rights reserved.
Reproduction in whole or in part is prohibited without the prior written permission of the copyright holder.
nAN-034 Setting up production test using DTM v1.0
Table of contents
1
1.1
Introduction............................................................................................................................................... 3
Prerequisites to the Application note ....................................................................................................... 3
2
Production test level ................................................................................................................................ 4
3
3.1
3.2
3.3
Setting up your production test ............................................................................................................ 5
Using Anritsu MT8852B as Tester ............................................................................................................... 5
Using a Nordic Semiconductor Development Kit as Tester.............................................................. 6
Enable DTM on DUT ........................................................................................................................................ 8
4
Exceptions when Production test on nRF8002 based products...................................................... 9
5
Glossary .................................................................................................................................................... 10
6
References................................................................................................................................................ 11
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nAN-034 Setting up production test using DTM v1.0
1
Introduction
The main function of a production test is to verify that all the components are mounted correctly and have
correct values after assembling a device.
To perform a production test on a Bluetooth® low energy application, it is preferable to use a built-in
function called Direct Test Mode (DTM). The DTM enables testing of the RF parameters and is also used for
end-product qualification testing of the RF physical layer (RF PHY). All Bluetooth low energy products
include a UART interface that gives access to the Direct Test Mode (DTM).
The DTM has two main modes of operation; the transmit test mode and the receive test mode. In transmit
test mode, the Device Under Test (DUT) generates a predefined set of test packets. In receive test mode, the
DUT counts the number of test packets received.
This application note describes two alternatives for setting up a production test with DTM:
• By using Anritsu MT8852B Bluetooth Test Set
• Qualified by Bluetooth SIG
• Wide range of DTM test
• By using the nRF8001 Development Kit or the nRF51822 Development Kit together with a
computer as the tester
• Simple range of DTM tests
• Low cost
1.1
1.1.1
Prerequisites to the Application note
Hardware requirements
• nRF8001 Development Kit (nRF8001-DK) or nRF51822 Development Kit (nRF51822-DK)
• nRFgo Starter Kit (nRF6700)
1.1.2
Software requirements
• nRF8001 SDK or nRF51 SDK
• nRFgo Studio
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nAN-034 Setting up production test using DTM v1.0
2
Production test level
The level on the production test should be based on the fact that the RF circuitry on every chip from Nordic
Semiconductor is already tested, including both transmit and receive functionality. During your prototype
testing of a device, all the main parameters such as output power, range, and functionality are verified.
This means that the production test needed on every assembled device can be simplified compared to the
prototype testing.
Passing a production test using DTM will verify:
• The transceivers output power is sufficient, indicating that the matching network and
related circuitry are mounted correctly and have correct component values.
• The functionality of the device.
After the production test is passed, the device is ready to use.
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nAN-034 Setting up production test using DTM v1.0
3
Setting up your production test
3.1
Using Anritsu MT8852B as Tester
The Anritsu MT8852B supports Bluetooth low energy (BLE) DTM testing on a device by controlling the device
through a HCI or two-wire (UART) interface while measuring the RF performance. The UART interface is
available on all Nordic Semiconductor BLE devices. The Anritsu MT8852B can run BLE tests directly, or the
testing can be controlled from a computer.
The DUT is controlled by sending DTM commands over the UART interface. There are ready made BLE fulltests and quick-tests available from Anritsu, along with the possibility to create manual test scripts.
Untested
UART control lines
Coax
DUT
Anritsu
MT8852B
Shielded box
Tested
Figure 1 Using Anritsu MT8852B as Tester
To access the documentation, software, operation manuals, and supported test modes for the Anritsu
MT8822B, please visit www.anritsu.com.
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nAN-034 Setting up production test using DTM v1.0
3.2
Using a Nordic Semiconductor Development Kit as Tester
To be able to use a Nordic Semiconductor Development Kit as a tester, an attenuator is needed between the
DUT and the tester, see Figure 2.
The attenuator must be adjusted so the RF output power is just above a threshold set on the Tester. If the
output power from the DUT is lower than expected, it will end up under the threshold and identified by the
Tester as a faulty device.
The difference between a functional and a faulty matching network is at least 10 dB, so it is possible to use a
Tester with an attenuator to differentiate between a good and a bad DUT.
Figure 2 shows a typical setup with a PCB module with SMA connector from nRF8001-DK or nRF51822-DK,
together with a computer acting as a Tester in a production test setup. The PCB module with SMA connector
from the Development Kit will work as the Lower Tester (RF PHY) and the computer will work as the Upper
Tester (UART control lines).
UART to USB cable or RS232 level shifter for PC COM port
Untested
UART control lines (connected to a bed of nails)
Coax
DUT
Shielded box
Attenuator
Coax
nRF DK
module w/SMA
UART
Computer
Shielded box
Lower Tester
Tested
Figure 2 Setup with PCB module with SMA connector as Lower Tester
Page 6 of 13
Upper Tester
nAN-034 Setting up production test using DTM v1.0
Figure 3 shows a simplified setup of Figure 2 on page 6. This setup will use the DTM_ENABLE pin to setup
transmit mode directly on the DUT, without use of UART control lines (See Section 3.3 “Enable DTM on DUT”
on page 9. for details). The computer should now run the DTM receive test only. This setup is sufficient to
verify production test levels as described in Chapter 2 on page 4.
UART to USB cable or RS232 level shifter for PC COM port
Untested
Coax
DUT
Shielded box
Attenuator
Coax
nRF DK
module w/SMA
UART
Computer
Shielded box
Lower Tester
Tested
Figure 3 Simple setup with PCB module with SMA connector as Tester
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Upper Tester
nAN-034 Setting up production test using DTM v1.0
3.2.1
Hardware requirements
To use the Nordic Semiconductor Development Kit as the tester, requires two COM ports on the computer,
one to control the PCB with SMA connector and one to control the DUT. It is possible to use FTDI based USB
to Serial (TTL 3.3 V) adapters on the computer to connect to the UART control lines, or alternatively use
RS232 with level shifters.
An Nordic Semiconductor Development Kit consists of several PCB modules; however only the PCB module
with SMA connector can be used as Lower Tester in the production test. Set up the hardware for testing with
DTM as described in the respective Development Kit User Guides.
The PCB module with SMA connector and the attenuator should be placed within a shielded box, especially
if it is used in an environment with multiple DTM test stations in close proximity.
The DTM UART settings for the Development Kit modules:
• UART interface: TXD and RXD
• Baud rate: 19200
• Data bits: 8
• Stop bit: 1
• No parity
• No flow control (no RTS or CTS)
3.2.2
Computer Software
The computer (Upper Tester) software is written in the Python programming language and consists of a
DTM library, an example script, and a readme file. The software is enclosed in the zip-file together with this
application note. The software has been run and tested on a Windows 7 computer. The software can be
ported to other platforms that support Python.
The DTM library can set up different DTM modes through UART commands as described in the Bluetooth
specifications Ver 4.0, Vol 6, part F. The example script uses the DTM library to control both Tester and DUT
over their respective COM ports on the computer.
The DTM library supports both receive and transmit test modes, and will output Packet Error Rate (PER) for
both modes. Typically a PER of > 30% in either mode can be used to detect a failing DUT.
Refer to the readme file included in the attached software for documentation on the requirements and
usage of the software.
3.2.3
Setting attenuation level
The attenuator level should be set by using a golden sample as DUT. This golden sample is a tested
prototype device that meets the requirements in terms of output power and range for your product. Place
the golden sample in the shielded box as DUT, and carefully adjust the attenuator to the highest attenuator
setting which still allows the golden sample to pass the DTM test. Decrease the attenuation level by 4 to 6 dB
to allow for some production variation, this is the setting you should use for the test station. Repeat this
procedure to set attenuation level for every test station.
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nAN-034 Setting up production test using DTM v1.0
3.3
Enable DTM on DUT
The Tester must have access to 5 test points on the DUT to run the DTM test.
Test points
Description
Comment
1
VSS (Ground)
Power supply
2
VCC
Power supply
3
DTM_ENABLE
Enable DTM test (optional)
4
TXD
UART control line
5
RXD
UART control lines
Table 1 Required pin connection for the DUT
The DTM_ENABLE pin is an optional pin that can be used by the application controller to enable the UART
control lines for DTM tests. For example, the DTM_ENABLE test pin can be an input pin with a pull up resistor,
and if this pin is pulled low externally, the application should enable the UART control lines for DTM tests.
The DTM_ENABLE pin can also be used to setup transmit mode directly, without the use of the UART control
lines.
The actual baud rate used by the DUT depends on the BLE chip used in the product. For some BLE chips the
baud rate is fixed, while for others the baud rate can be modified. Refer to the specific product specification
or source code for details.
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nAN-034 Setting up production test using DTM v1.0
4
Exceptions when Production test on nRF8002 based products
Note: The nRF8002 Direct Test Mode (DTM) is not available after the configuration
of the nRF8002 is placed in OTP.
Typically the DUT should be a preprogrammed module with application firmware or configuration;
however, for the nRF8002 the DTM test is only available before the configuration is locked in OTP. The
nRF8002 can receive DTM commands over the UART after power is applied and before any configuration is
locked to OTP.
This means that for products based on the nRF8002 the configuration should be written after the DTM test is
passed. This will still verify that the hardware is fully operational and meet the requirements of the final
product.
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nAN-034 Setting up production test using DTM v1.0
5
Glossary
Term
Description
RF PHY
Radio Frequency Physical layer - including
crystal, matching network and antenna
OTP
One Time Programmable Memory
DK
Development Kit
DTM
Direct Test Mode
DUT
Device Under Test
Tester
The actual hardware executing the DTM test,
can be split in a Lower and Upper Tester
BLE
Bluetooth low energy
PER
Packet Error Rate
UART
Universal asynchronous receiver/transmitter
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nAN-034 Setting up production test using DTM v1.0
6
References
How to enable the DTM mode on the chip in use:
• nRF8001 - Use the ACI Test command with the enable DTM over ACI option or DTM over
UART as defined in the nRF8001 Product Specification. The nRF8001 Product Specification
can be found on www.nordicsemi.com. Read the Development Kit User Guide for the
nRF8001 for more information on DTM.
• nRF518xx and other nRF devices - Read the Development Kit User Guide for the respective
chip on how to configure and enable DTM. The Development Kit User Guide for the
respective chip can be found on www.nordicsemi.com.
See Bluetooth specification Ver 4.0, Vol 6, part F for DTM command word format and options. The Bluetooth
specification can be found on www.bluetooth.org.
See RF Performance Test Guidelines, White Paper nWP-006, that describes how to run various RF front end
tests. The White Paper can be found on www.nordicsemi.com/eng/Support/Whitepapers.
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nAN-034 Setting up production test using DTM v1.0
Liability disclaimer
Nordic Semiconductor ASA reserves the right to make changes without further notice to the product to
improve reliability, function or design. Nordic Semiconductor ASA does not assume any liability arising out
of the application or use of any product or circuits described herein.
Life support applications
Nordic Semiconductor’s products are not designed for use in life support appliances, devices, or systems
where malfunction of these products can reasonably be expected to result in personal injury. Nordic
Semiconductor ASA customers using or selling these products for use in such applications do so at their
own risk and agree to fully indemnify Nordic Semiconductor ASA for any damages resulting from such
improper use or sale.
Contact details
For your nearest distributor, please visit http://www.nordicsemi.com.
Information regarding product updates, downloads, and technical support can be accessed through your
My Page account on our homepage.
Main office: Otto Nielsens veg 12
7052 Trondheim
Norway
Mailing address: Nordic Semiconductor
P.O. Box 2336
7004 Trondheim
Norway
Phone: +47 72 89 89 00
Fax: +47 72 89 89 89
Revision History
Date
Version
Description
April 2013
1.0
First release
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