NRF52840-PDK

nRF52840 Preview Development Kit v0.11.x User Guide v1.2 4440_025 v1.2 / 2018-01-19 Contents Revision history. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv 1 Introduction. 5 2 Minimum requirements. 3 Kit content. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.1 Hardware content . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Downloadable content . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3 Related documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 7 8 4 Getting started. 9 5 Nordic tools and downloads. 6 Start developing. 7 Interface MCU. 8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 7.1 IF Boot/Reset button . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2 Virtual COM port . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2.1 Dynamic HWFC handling . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3 Swapping interface MCU firmware . . . . . . . . . . . . . . . . . . . . . . . . . 7.4 MSD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 13 14 14 15 Hardware description. 16 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.1 Hardware drawings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2 Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3 Power supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3.1 5 V power sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3.2 VDD power sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3.3 Interface MCU power . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3.4 nRF52840 power source . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3.5 nRF52840 direct supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.4 Operating modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.4.1 USB detect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.4.2 nRF only mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.4.3 Signal switches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.5 External memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.6 Connector interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.7 Buttons and LEDs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.8 32.768 kHz crystal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.9 Measuring current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.9.1 Preparing the development kit board . . . . . . . . . . . . . . . . . . . . . . 8.9.2 Using an oscilloscope for current profile measurement . . . . . . . . . . . . . . . 8.9.3 Using an ampere-meter for current measurement . . . . . . . . . . . . . . . . . 8.10 RF measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.11 Debug input and trace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.12 Debug output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.13 NFC antenna interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4440_025 v1.2 ii 16 16 17 18 18 20 21 22 22 22 23 23 25 26 28 29 30 31 31 32 33 34 35 36 8.14 Extra op-amp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.15 Solder bridge configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 37 Legal notices. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 4440_025 v1.2 iii Revision history Date Version Description January 2018 1.2 Updated to match PDK v0.11.x February 2017 1.1 Updated: • Swapping interface MCU firmware on page 14 • MSD on page 15 December 2016 4440_025 v1.2 1.0 First release iv 1 Introduction The nRF52840 Preview Development Kit (DK) includes hardware, firmware source code, documentation, hardware schematics, and layout files. nRF52840 Preview Development Kit Product Brief The key features of the development kit are: • • • • • • • • • • nRF52840 flash-based ANT™/ANT+™, Bluetooth® Low Energy SoC solution Buttons and LEDs for user interaction I/O interface for Arduino form factor plug-in modules SEGGER J-Link OB Debugger with debug out functionality UART interface through virtual COM port USB Flash memory Drag-and-drop mass storage device (MSD) programming Supporting NFC-A listen mode Mbed Enabled For access to firmware source code, hardware schematics, and layout files, see www.nordicsemi.com. 4440_025 v1.2 5 2 Minimum requirements Before you start, check that you have the required hardware and software. Hardware requirements • Personal computer (PC) or Mac • Micro-USB 2.0 cable Software requirements • Operating system: Windows 7, Windows 8, Windows 10, MacOS, or Linux • SEGGER J-Link Software 4440_025 v1.2 6 3 Kit content The nRF52840 Preview DK consists of hardware, access to software components, reference design files, and documentation. 3.1 Hardware content The nRF52840 Preview Development Kit (DK) contains the development kit board PCA10056 and an NFC antenna. Figure 1: nRF52840 Preview DK board (PCA10056) and NFC antenna 3.2 Downloadable content The nRF52840 Preview DK downloadable content includes the hardware files. • In the nRF5 SDK, you can find precompiled application firmware examples. Hardware files Schematics, layout, bill of materials, and Gerber files for nRF52840 Preview DK are included in a zip file. • nRF52840 Preview DK hardware files 4440_025 v1.2 7 Kit content 3.3 Related documentation In addition to the information in this document, you may need to consult other documents. Nordic documentation • nRF52840 Objective Product Specification • nRF52840 Compatibility Matrix • nRF52840 Errata 4440_025 v1.2 8 4 Getting started Before you start developing, complete a few steps to set up the hardware and download the required software. Before you start: • Unpack the kit. • Check Minimum requirements on page 6. Follow the steps below to set up your kit: 1. Connect the NFC antenna to the connector marked NFC. 2. To power up the board: a) Connect a micro-USB 2.0 cable to the USB connector J2 on the nRF52840 Preview DK and the other end to one of your PC's USB host port. In addition to providing power to the board, the USB connection supports target programming. b) Slide the power switch SW8 to the ON position. A pop-up may appear. You can ignore it. Check that LED1 has started pulsating. For more information, see Buttons and LEDs on page 28. Open Windows Explorer to check that the nRF52840 Preview DK has appeared as a removable drive named "JLINK". This allows you to program the chip on the board. 3. Set up the software following the instructions in Nordic tools and downloads in nRF5 Getting Started. The actual software required depends on your OS and development IDE. 4. To set up a connection between your smart phone and the PDK, enable NFC on your smart phone and bring your phone close to the PDK. Your phone will prompt you to open Getting started with the nRF52840 Development Kit. This page contains a link that makes it easy to install the nRF Toolbox mobile app. 4440_025 v1.2 9 5 Nordic tools and downloads Once you have your kit set up you can start developing. Our software tools help you develop and test your device through all the steps in the software development cycle. Development IDE Pick one of the IDEs with a compiler supported by Nordic: IDE Windows Linux OSX MDK-ARM Keil µVision Yes No No GNU/GCC Yes Yes Yes IAR Yes No No SEGGER Embedded Studio (SES) Yes Yes Yes Essential tools To program our devices you need to download these Nordic tools. Tool Description Download Documentation Protocol SDK - Software Development Kit Application examples, source files, SoftDevices Windows/Linux nRF5 SDK BLE/ANT nRF5x Command Line Tools Collection of command line tools, like nrfjprog, mergehex nRF5x Tools Windows32 nRF5x Command Line Tools BLE/ANT nRF5x Tools Linux32 nRF5x Tools Linux64 nRF5x Tools OSX Optional tools These tools are not essential, but we recommend that you use them. 4440_025 v1.2 10 Nordic tools and downloads Tool Description Download Documentation Protocol nRFgo Studio Programming and erasing chips Windows32 Help file BLE/ANT Wireless protocol stack library Click the Download tab on: nRF52 Series SDS BLE/ANT SoftDevice Windows64 nRF52840 Product page nRF51 Series SDS nRF52832 Product page nRF51822 Product page nRF51422 Product page Master Control Panel Peer device emulator for computers Windows32 Help file nRF Connect for desktop Peer device emulator for computers nRF Connect for OS- nRF Connect Bluetooth Low Energy X BLE Windows64 BLE nRF Connect for Ubuntu Linux nRF Connect for Windows nRF Connect for mobile Peer device emulator app for smartphones Nordic nRF Toolbox app App that contains all Android v4.3 or later the Nordic apps IOS v8 or later BLE Android v4.3 or later IOS v8 or later BLE Windows Phone v8.1 or later nRF5x pynrfjprog A simple Python interface for the nrfjprog DLL nRF5x pynrfjprog nRF5x pynrfjprog BLE/ANT ANTware II Peer device emulator for the ANT protocol running on computers ANTware II ANTware II ANT nRF Sniffer Monitors on-air traffic nRF Sniffer download nRF Sniffer BLE See also Nordic mobile apps for a list of available Bluetooth Low Energy mobile apps for iOS, Android and Windows Phones. 4440_025 v1.2 11 6 Start developing After you have set up the development kit and installed the toolchain, it is time to start developing. There are several ways to continue from here. For more information, see the following nRF5 SDK instructions : • Running precompiled examples See how you can quickly test a precompiled example without having to use the full toolchain, it is a matter of copying and pasting a precompiled HEX file onto your development kit board. • Compiling and running a first example Test that you have set up your toolchain correctly by compiling, programming and running a very simple example. • Running examples that use a SoftDevice Before you can run more advanced examples that use Bluetooth or ANT, you must first program the SoftDevice on the board. 4440_025 v1.2 12 7 Interface MCU The interface MCU on the nRF52840 Preview Development Kit (DK) board can run either SEGGER J-Link OB or mbed OB interface firmware and is used to program and debug the firmware of the nRF52840 SoC. Figure 2: Interface MCU 7.1 IF Boot/Reset button The nRF52840 Preview DK board is equipped with an IF Boot/Reset button (SW5). This button is connected to the interface MCU on the board and has two functions: • Resetting the nRF52840 SoC. • Entering bootloader mode of the interface MCU. During normal operation the button will function as a reset button for the nRF52840 SoC. For this to work, pin reset on P0.18 needs to be enabled in the SoC. The button is also used to enter the bootloader mode of the interface MCU. To enter the bootloader mode, keep the reset button pressed while powering up the board until LED5 starts to blink. You can power up the board either by disconnecting and reconnecting the USB cable or by toggling the power switch (SW8). Note: Pin reset can be enabled by defining the CONFIG_GPIO_AS_PINRESET variable in the project settings. This can be done, for example, by defining the preprocessor symbol in Keil. Go to Project > Options for Target > C/C++ > Preprocessor Symbols > Define and add the CONFIG_GPIO_AS_PINRESET variable after NRF52840_XXAA. This functionality can be removed by using nrfjprog.exe with arguments --recover -f NRF52. 7.2 Virtual COM port The onboard interface MCU features a UART interface through a virtual COM port. The virtual COM port has the following features: 4440_025 v1.2 13 Interface MCU • Flexible baud rate setting up to 1 Mbps.1 • Dynamic hardware flow control (HWFC) handling. • Tri-stated UART lines when no terminal is connected. The table below shows an overview of the UART connections on nRF52840 and the interface MCU. GPIO nRF52840 nRF52840 UART P0.05 RTS P0.06 TXD P0.07 CTS P0.08 RXD Table 1: Relationship of UART connections on nRF52840 and interface MCU The UART signals are routed directly to the interface MCU. The UART pins connected to the interface MCU are tri-stated when no terminal is connected to the virtual COM port on the computer. Note: The terminal software used must send a DTR signal to configure the UART interface MCU pins. The P0.05 (RTS) and P0.07 (CTS) can be used freely when HWFC is disabled on the SoC. Note: The mbed OB interface does not support HWFC through the virtual COM port. 7.2.1 Dynamic HWFC handling When the interface MCU receives a DTR signal from a terminal, it performs automatic hardware flow control (HWFC) detection. Automatic HWFC detection is done by driving P0.07 (CTS) from the interface MCU and evaluating the state of P0.05 (RTS) when the first data is sent or received. If the state of P0.05 (RTS) is high, HWFC is assumed not to be used. If HWFC is not detected, both CTS and RTS can be used freely by the nRF application. After a power-on reset of the interface MCU, all UART lines are tri-stated when no terminal is connected to the virtual COM port. Due to the dynamic HWFC handling, if HWFC has been used and detected, P0.07 (CTS) will be driven by the interface MCU until a power-on reset has been performed or until a new DTR signal is received and the detection is redone. To ensure that the UART lines are not affected by the interface MCU, the solder bridges for these signals can be cut and later resoldered if needed. This might be necessary if UART without HWFC is needed while P0.05 (RTS) and P0.07 (CTS) are used for other purposes. 7.3 Swapping interface MCU firmware The onboard interface MCU is factory-programmed with an mbed-compliant bootloader. This feature makes it possible to swap the interface firmware between the factory-preloaded SEGGER J-Link OB and the mbed interface firmware. 1. Download the mbed interface firmware and the J-Link OB image from www.nordicsemi.com. 2. Enter the bootloader. 1 Baud rate 921 600 is not supported through the virtual COM port. 4440_025 v1.2 14 Interface MCU See section IF Boot/Reset button on page 13 on how to enter the bootloader. 3. To swap the interface MCU firmware, drag the interface image (.bin) into the mounted bootloader drive on the connected computer. 4. Power cycle the board. Note: • The J-Link serial number is linked to the interface MCU and will not change even when swapping the interface MCU firmware. • When in bootloader mode, do not drag and drop any files except those downloaded from www.nordicsemi.com for use with the interface MCU. If a wrong file is used, it can overwrite the bootloader and ruin the interface MCU firmware without the possibility of recovery. 7.4 MSD The interface MCU features a mass storage device (MSD). This makes the development kit appear as an external drive on your computer. This drive can be used for drag-and-drop programming. However, files cannot be stored on this drive. By copying a HEX file to the drive, the interface MCU will program the file to the device. Note: • Windows might try to defragment the MSD part of the interface MCU. If this happens, the interface MCU will disconnect and be unresponsive. To return to normal operation, the development kit must be power cycled. • Your antivirus software might try to scan the MSD part of the interface MCU. Some antivirus programs trigger a false positive alert in one of the files and quarantine the unit. If this happens, the interface MCU will become unresponsive. • If the computer is set up to boot from USB, it can try to boot from the development kit if the development kit is connected during boot. This can be avoided by unplugging the development kit before a computer restart, or changing the boot sequence of the computer. You can also disable the MSD of the kit by using the msddisable command in J-Link Commander. To enable, use the msdenable command. These commands take effect after a power cycle of the development kit and stay this way until changed again. 4440_025 v1.2 15 8 Hardware description The nRF52840 Preview Development Kit (DK) board PCA10056 can be used as a development platform for the nRF52840 SoC. It features an onboard programming and debugging solution. In addition to radio communication, the nRF52840 SoC can communicate with a computer through USB and a virtual COM port provided by the interface MCU. 8.1 Hardware drawings nRF52840 Preview DK hardware drawings show both sides of the PCA10056 board. Figure 3: nRF52840 Preview DK board front view Figure 4: nRF52840 Preview DK board back view 8.2 Block diagram The nRF52840 Preview DK block diagram shows the connections between the different blocks. 4440_025 v1.2 16 Hardware description GPIO LEDs Buttons IF Boot/Reset nRF only mode switch Debug out IF MCU USB Battery External supply External memory Matching network Interface MCU Analog switch Analog switch Current measurement Osc 16 MHz nRF power source switch Osc 32.768 kHz Li-ion Debug in Power supply circuitry nRF52840 Power switch nRF USB Figure 5: nRF52840 Preview DK block diagram 8.3 Power supply The nRF52840 Preview DK board has multiple power options. The power options are: • • • • • • USB connector J2 for the interface MCU (5 V) USB connector J3 for the nRF52840 (5 V) Lithium polymer (Li-Po) battery connectors J6 or P27 (2.5–5.0 V) VIN 3–5 pin on P20 (3.0–5.0 V) External supply on P21 (1.7–3.6 V) Coin cell battery Figure 6: Power supply options (board front) 4440_025 v1.2 17 Antenna RF connector Hardware description Figure 7: Power supply options (board back) 8.3.1 5 V power sources The nRF52840 Preview DK board has a 5 V boost regulator. It gives a stable 5 V output from four possible sources: • • • • USB connector J2 for the interface MCU USB connector J3 for the nRF52840 Li-Po polymer battery connectors (J6 or P27) VIN 3–5 V pin on P20 Each of these sources has a reverse protection diode to prevent current flowing in the wrong direction if multiple sources are connected at the same time. Figure 8: 5 V regulator and protecting diodes 8.3.2 VDD power sources The main board supply (VDD) can be sourced from the 5 V domain, external power supply, and coin cell battery. For the 5 V domain, there are two regulators, one fixed 3 V buck regulator and one voltage follower regulator that follows the VDD_nRF voltage. The coin cell battery and external power supply are not regulated. • 5 V domain: • Fixed 3 V buck regulator • VDD_nRF voltage follower • External power supply • Coin cell battery For more information about power sources, see section nRF52840 power source on page 21. 4440_025 v1.2 18 Hardware description The power sources are routed through a set of load switches, which is controlled by logic to give the correct priority of the power sources. If the high voltage regulator of the nRF52840 is used, the board will be supplied from the VDD_nRF voltage follower regardless of the state of the other power sources. Figure 9: Power supply circuitry The power switches work in the way that the body diode of the internal transistor powers the VSUPPLY net, which supplies the gates controlling the enable signal of the switches. If 5 V is present, the switches 4440_025 v1.2 19 Hardware description for external supply and battery are disabled. If external supply is present, the switch for the battery is disabled. The power switches can be bypassed by shorting one or more solder bridges. Power source Power switch bypass Voltage level Regulator SB34 3.0 V Coin cell battery SB35 Battery External supply SB36 1.7 V–3.6 V Table 2: Power switch bypass solder bridges Figure 10: Power switch bypass solder bridges Note: Connect only one power source at a time. Shorting the solder bridges removes the reverse voltage protection. 8.3.3 Interface MCU power The power for the interface MCU is routed through two load switches, one for the VDD supply and one for the USB supply. This makes it possible to disconnect the interface MCU from the power domain when not in use. Figure 11: Interface MCU power switch 4440_025 v1.2 20 Hardware description These switches are controlled by the presence of a USB connected to the interface MCU USB connector (J2), and the state of the nRF only switch (SW6). See section Operating modes on page 22 for more information. 8.3.4 nRF52840 power source The nRF52840 Preview DK board has a power source switch (SW9) for selecting between three power sources for the nRF52840 SoC. The three positions of the switch are: • VDD (default) • Li-Po • USB Figure 12: nRF52840 power source switch The nRF52840 SoC has a high voltage buck regulator that can support up to 5 V input. In the VDD position, the SoC is powered either from the on-board buck regulator, coin cell battery, or external supply (P21). In the Li-Po position, the high voltage regulator of the SoC is supplied directly from the Li-Po battery connectors (J6 or P27). In the USB position, the USB high voltage regulator gets power from the nRF52840 USB connector (J3). When the high voltage regulator is used, the VDD_nRF voltage can be set by the firmware of the SoC. To make sure the rest of the board has the same voltage level, the VDD of the board is sourced by a regulator following the VDD_nRF voltage when the high voltage regulator is used. Figure 13: VDD_nRF voltage follower and switch 4440_025 v1.2 21 Hardware description To make sure that the nRF52840 is not powered when the nRF power switch (SW8) is OFF, two load switches are used, one for the high voltage regulator (U23) and one for the USB supply (U22). These switches are controlled by VDD. 8.3.5 nRF52840 direct supply It is possible to power the SoC directly from a source without powering the rest of the board from the same source. The external source can be connected to the external supply connector (P21) and the VEXT->nRF switch (SW10) put in the ON position. The nRF power source switch (SW9) must be in the VDD position, and the allowed voltage range is 1.7–3.6 V. Figure 14: VEXT->nRF switch (SW10) Since it is only the nRF52840 SoC that is supplied from this source, it is recommended to supply the VDD domain from a different source (coin cell battery or USB) to prevent the pins of the SoC to be connected to unpowered devices. To prevent leakage due to voltage differences, the board should be set in the nRF only mode, see section Operating modes on page 22. Note: To reduce trace length and parasitic components, the external memory is connected to the SoC directly instead of using analog switches. It is recommended to cut solder bridges to avoid leakage, see section External memory on page 25. 8.4 Operating modes The nRF52840 Preview DK board has various modes of operation. 8.4.1 USB detect To detect when USB for the interface MCU is connected, there is a circuit sensing the VBUS of USB connector J2. When the USB cable is connected, the VDD is propagated to the USB_DETECT signal. 4440_025 v1.2 22 Hardware description Figure 15: USB detect 8.4.2 nRF only mode The nRF only mode disconnects the interface MCU and LEDs from the SoC using analog switches. This is done to isolate the chip on the board as much as possible, and can be of use when measuring currents on low-power applications. Figure 16: nRF only switch (SW6) 8.4.3 Signal switches On the nRF52840 Preview DK board, there are multiple analog switches that are used to connect and disconnect signals based on different scenarios. 4440_025 v1.2 23 Hardware description Figure 17: Signal switches The USB and SW6 control the signal switches by using USB_DETECT as an input to SW6. Therefore, the interface MCU can be disconnected either by unplugging the USB cable in J2 or by toggling SW6. The signal controls a set of switches (U5, U6, U7) that break the connection between the nRF52840 and the interface MCU, and control the power for the interface MCU. For more information, see section Interface MCU power on page 20. Switches U5 and U6 break the connection of the UART lines and SWD/RESET lines. In addition, the signal controls the routing of the RESET signal depending on user preference when the interface MCU is connected/disconnected. • When the interface MCU is disconnected, cutting SB42 will disconnect the IF Boot/Reset button from the reset pin (P0.18) of nRF52840. • When the interface MCU is disconnected, shorting SB45 will connect the RESET pin in the Arduino interface to the reset pin (P0.18) of nRF52840. 4440_025 v1.2 24 Hardware description • When the interface MCU is connected, shorting SB46 will connect the RESET pin in the Arduino interface to the BOOT input of the interface MCU. • Shorting SB43 will connect the RESET pin in the Arduino interface to the IF Boot/Reset button. • Shorting SB44 will connect the RESET pin in the Arduino interface to the reset pin (P0.18) of nRF52840. When a shield is connected, there are two analog switches connecting the pull-up resistors to the I2C bus lines (SDA and SCL). This function is using one ground pin on the Arduino shield to control the switch. This feature can be disabled by cutting SB33. To permanently enable pull-up resistors, short SB32. Figure 18: Solder bridges: Shield detect and reset behavior The last switch (U8) controls which GPIOs certain signals are routed to. This is due to some features using the same GPIOs as the Trace output by default. These analog switches are controlled by SW7. See chapter Debug input and trace on page 34 for more information. 8.5 External memory The nRF52840 Preview DK board has a 64 Mb external flash memory. The memory is a multi-I/O memory supporting both regular SPI and Quad SPI. The memory is connected to the chip using the following GPIOs: GPIO Flash memory pin Solder bridge for memory use (default: shorted) Solder bridge for GPIO use (default: open) P0.17 CS SB13 SB23 P0.19 SCLK SB11 SB21 P0.20 SIO_0/SI SB12 SB22 P0.21 SIO_1/SO SB14 SB24 P0.22 SIO_2/WP SB15 SB25 P023 SIO_3/HOLD SB10 SB20 Table 3: Flash memory GPIO usage and connecting solder bridges To use the GPIOs for a purpose other than the onboard external memory and have them available on the P24 connector, six solder bridges (SB10–SB15) must be cut and six solder bridges (SB20–SB25) must be shorted. See Figure 19: Configuring GPIOs for external memory on page 26 for details. 4440_025 v1.2 25 Hardware description Note: If debugging the QSPI communication is needed, the SB20–SB25 can be shorted without cutting SB10–SB15, but the pins should not be driven externally. Figure 19: Configuring GPIOs for external memory By default, the power supply of the external memory is coming from the VDD domain and it is controlled by the nRF only switch (SW6). In the nRF only mode, there are two optional power sources for keeping the external memory powered, VDD and VDD_nRF. If VDD_nRF is selected, the power consumption of the external memory will be added to the nRF52840 current measured on P22 or P23. See the following table for configuration: Power source Solder bridge Default state VDD_PER SB16 Shorted VDD SB17 Open VDD_nRF SB18 Open Table 4: Flash memory power source configuration 8.6 Connector interface Access to the nRF52840 GPIOs is available from connectors P2, P3, P4, P5, P6, and P24. The P1 connector provides access to ground and power on the nRF52840 Preview DK board. 4440_025 v1.2 26 Hardware description Figure 20: nRF52840 Preview DK board connectors Some of the signals are also available on connectors P7, P8, P9, P10, P11, and P12, which are on the bottom side of the board. By mounting pin lists on the connector footprints, the nRF52840 Preview DK board can be used as a shield for Arduino motherboards2 or other boards that follow the Arduino standard. For easy access to GPIO, power, and ground, the signals can also be found on the through-hole connectors P13–P17. Note: Some pins have default settings: • P0.00 and P0.01 are used for the 32.768 kHz crystal and are not available on the connectors. For more information, see section 32.768 kHz crystal on page 29. • P0.05, P0.06, P0.07, and P0.08 are used by the UART connected to the interface MCU. For more information, see section Virtual COM port on page 13. • P0.09 and P0.10 are by default used by NFC1 and NFC2. For more information, see section NFC antenna interface on page 36. • P0.11–P0.16 and P0.24–P0.25 are by default connected to the buttons and LEDs. For more information, see section Buttons and LEDs on page 28. • P0.17 and P0.19–P0.23 are by default connected to the external memory. For more information, see section External memory on page 25. 2 Only 3.3 V Arduino boards. 4440_025 v1.2 27 Hardware description When the nRF52840 Preview DK board is used as a shield together with an Arduino standard motherboard, the Arduino signals are routed as shown in the figure below. Figure 21: Arduino signals routing on the nRF52840 Preview DK board 8.7 Buttons and LEDs The four buttons and four LEDs on the nRF52840 Preview DK board are connected to dedicated GPIOs on the nRF52840 chip. Part GPIO GPIO alternative Solder bridge Button 1 P0.11 P1.07 - Button 2 P0.12 P1.08 - Button 3 P0.24 - Button 4 P0.25 - LED 1 P0.13 SB5 LED 2 P0.14 SB6 LED 3 P0.15 SB7 LED 4 P0.16 SB8 Table 5: Button and LED connection 4440_025 v1.2 28 Hardware description If P0.13–P0.16 are needed elsewhere, the LEDs can be disconnected by cutting the short on SB5–SB8, see figure Figure 22: Disconnecting the LEDs on page 29. Since P0.11 and P0.12 are used as a part of the Trace functionality, Button 1 and Button 2 can be moved to alternative GPIOs, see chapter Debug input and trace on page 34 for more information. Figure 22: Disconnecting the LEDs The buttons are active low, meaning that the input will be connected to ground when the button is activated. The buttons have no external pull-up resistor, and therefore, to use the buttons, the P0.11, P0.12, P0.24, P0.25 pins must be configured as an input with an internal pull-up resistor. The LEDs are active low, meaning that writing a logical zero ('0') to the output pin will illuminate the LED. Figure 23: Button and LED configuration 8.8 32.768 kHz crystal The nRF52840 SoC can use an optional 32.768 kHz crystal (X2) for higher accuracy and lower average power consumption. On the nRF52840 Preview DK board, P0.00 and P0.01 are by default used for the 32.768 kHz crystal and are not available as GPIO on the connectors. Note: When using ANT/ANT+, the 32.768 kHz crystal (X2) is required for correct operation. If P0.00 and P0.01 are needed as normal I/Os, the 32.768 kHz crystal can be disconnected and the GPIO routed to the connectors. Cut the shorting track on SB1 and SB2, and solder SB3 and SB4. See the following figure for reference. 4440_025 v1.2 29 Hardware description Figure 24: Configuring P0.00 and P0.01 Figure 25: 32.768 kHz crystal and SB1–SB4 schematic 8.9 Measuring current The current drawn by the nRF52840 SoC can be monitored on the nRF52840 Preview DK board. There are several types of test equipment that can be used to measure current, and each type has some advantages and some disadvantages. The test equipment types are: • • • • Power analyzer Oscilloscope Ampere-meter Power Profiler Kit Power analyzer and Power Profiler Kit measurements will not be described in the present document. For more information on Power Profiler Kit, see Power Profiler Kit User Guide. For instructions for measuring, see sections Using an oscilloscope for current profile measurement on page 31 and Using an ampere-meter for current measurement on page 32. The nRF52840 SoC has two possible power supplies, VDD (1.7–3.6 V) and VDDH (2.5–5.5 V). The nRF52840 Preview DK is prepared for measuring current on both domains. Only the VDD domain current measurement is described here, but the approach is the same with the VDDH supply. See the following table for the corresponding components: 4440_025 v1.2 30 Hardware description Component VDD VDDH Measurement connector P22 P23 Solder bridge SB40 SB41 Series resistor R90 R91 Table 6: Components for current measurement on VDD and VDDH Note: When measuring the current consumption: • It is not recommended to use a USB connector to power the board during current measurements. However, when measuring current on an application using the USB interface of the nRF52840 SoC, the USB must be connected. It is recommended to power the board from a coin cell battery, external power supply on connector P21 (1.7–3.6 V), or through the Li-Po connector J6 or P27 (2.5–5.0 V). • The current measurements will become unreliable when a serial terminal is connected to the virtual COM port. • After programming the nRF52840 SoC, the USB for the interface MCU must be disconnected. For more information on current measurement, see the tutorial Current measurement guide: Introduction. 8.9.1 Preparing the development kit board To measure current, you must first prepare the board. The suggested configurations actually split the power domains for the nRF52840 SoC and the rest of the board. Figure 26: Prepare the development kit board for current measurements • To put P22 in series with the load, cut the PCB track shorting solder bridge SB40. • To restore normal kit function after measurement, solder SB9 or apply a jumper on P22. • To reprogram the nRF52840 SoC while the board is prepared for current measurements, remove measurement devices from P22, and then connect the USB cable. 8.9.2 Using an oscilloscope for current profile measurement An oscilloscope can be used to measure both the average current over a given time interval and capture the current profile. 4440_025 v1.2 31 Hardware description Make sure you have prepared the development kit board as described in section Preparing the development kit board on page 31. 1. Mount a 10 Ω resistor on the footprint for R90. 2. Connect an oscilloscope in differential mode or similar with two probes on the pins of the P22 connector as shown in Figure 27: Current measurement with oscilloscope on page 32. 3. Calculate or plot the instantaneous current from the voltage drop across the 10 Ω resistor by taking the difference of the voltages measured on the two probes. The voltage drop will be proportional to the current. The 10 Ω resistor will cause a 10 mV drop for each 1 mA drawn by the circuit being measured. The plotted voltage drop can be used to calculate the current at a given point in time. The current can then be averaged or integrated to analyze current and energy consumption over a period. Figure 27: Current measurement with oscilloscope Some tips to reduce noise: • Use probes with 1× attenuation • Enable averaging mode to reduce random noise • Enable high resolution function if available Use a minimum of 200 kSa/s (one sample every 5 µs) to get the correct average current measurement. 8.9.3 Using an ampere-meter for current measurement The average current drawn by the nRF52840 SoC can be measured using an ampere-meter. This method will monitor the current in series with the nRF device. Make sure you have prepared the development kit board as described in section Preparing the development kit board on page 31. Connect an ampere-meter between the pins of connector P22 as shown in the figure below. 4440_025 v1.2 32 Hardware description Figure 28: Current measurement with an ampere-meter Note: An ampere-meter will measure the average current drawn by the nRF52840 SoC if: • The SoC is in a state where it draws a constant current, or, the activity on the device changing load current, like BLE connection events, is repeated continuously and has a short cycle time (less than 100 ms) so that the ampere-meter will average whole load cycles and not parts of the cycle. • The dynamic range of the ampere-meter is wide enough to give accurate measurements from 1 µA to 15 mA. • Recommendation: Use a true RMS ampere-meter. 8.10 RF measurements The nRF52840 Preview DK board is equipped with a small coaxial connector (J1) for conducting measurements of the RF signal using a spectrum analyzer. The connector is of SWF type (Murata part no. MM8130-2600) with an internal switch. By default, when no cable is attached, the RF signal is routed to the onboard trace antenna. A test probe is available (Murata part no. MXHS83QE3000) with a standard SMA connection on the other end for connecting instruments (the test probe is not included with the kit). When connecting the test probe, the internal switch in the SWF connector will disconnect the onboard antenna and connect the RF signal from the nRF52840 SoC to the test probe. 4440_025 v1.2 33 Hardware description Figure 29: Connecting a spectrum analyzer The connector and test probe will add loss to the RF signal, which should be taken into account when measuring, see the following table: Frequency (MHz) Loss (dB) 2440 1.0 4880 1.7 7320 2.6 Table 7: Typical loss in connector and test probe 8.11 Debug input and trace The Debug in connector (P18) makes it possible to connect external debuggers for debugging when the interface MCU USB cable is not connected or the board is in nRF only mode. Figure 30: Debug input and TRACE connectors 4440_025 v1.2 34 Hardware description For trace, a footprint for a 20-pin connector is available (P25). If trace functionality is required, a 2×10 pin 1.27 mm pitch surface mount pin header can be mounted. Some of the trace pins are by default used for other functionality on the board. By sliding the TRACE switch (SW7) from Def. to Alt., the functionality is moved to other GPIOs. See the following table: GPIO Trace Default use Optional GPIO P0.07 TRACECLK UART CTS P0.04 P1.00 TRACEDATA[0] P0.11 TRACEDATA[1] Button 1 P1.07 P0.12 TRACEDATA[2] Button 2 P1.08 P1.09 TRACEDATA[3] Table 8: Default and Trace GPIOs 8.12 Debug output The nRF52840 Preview DK board supports programming and debugging external boards with nRF51 or nRF52 SoCs. To debug an external board with SEGGER J-Link OB IF, connect to the Debug out connector (P19) with a 10-pin cable. Figure 31: Debug output connector When the external board is powered, the interface MCU will detect the supply voltage of the board and program/debug the target chip on the external board instead of the onboard nRF52840 SoC. Note: The voltage supported by external debugging/programming is VDD voltage. Normally, this is 3 V when running from USB, but if the onboard nRF52840 SoC is supplied from either USB or LiIon, the nRF power source switch (SW9) is in either Li-Po or USB position, and VDD can be set by the nRF52840 firmware. Make sure the voltage level of the external board matches the VDD of the nRF52840 Preview DK. You can also use P20 as a debug out connection to program shield-mounted targets. For both P19 and P20, the interface MCU will detect the supply voltage on the mounted shield and program/debug the target. If the interface MCU detects target power on both P19 and P20, it will by default program/debug the target connected to P19. 4440_025 v1.2 35 Hardware description If it is inconvenient to have a separate power supply on the external board, the nRF52840 Preview DK board can supply power through the Debug out connector (P19). To enable this, short solder bridge SB47. Note that as long as SB47 is shorted, it is not possible to program the onboard nRF52840 SoC even if the external board is unplugged. 8.13 NFC antenna interface The nRF52840 Preview DK board supports a near field communication (NFC) tag. NFC-A listen mode operation is supported on the nRF52840 SoC. The NFC antenna input is available on connector J5 on the nRF52840 Preview DK board. Figure 32: NFC antenna connector NFC uses two pins, L24 (NFC1) and J24 (NFC2), to connect the antenna. These pins are shared with GPIOs (P0.09 and P0.10) and the PROTECT field in the NFCPINS register in UICR defines the usage of these pins and their protection level against abnormal voltages. The content of the NFCPINS register is reloaded at every reset. Note: The NFC pins are enabled by default. NFC can be disabled and GPIOs enabled by defining the CONFIG_NFCT_PINS_AS_GPIOS variable in the project settings. This can be done by defining the preprocessor symbol in Keil. Go to Project > Options for Target > C/C++ > Preprocessor Symbols > Define and add the CONFIG_NFCT_PINS_AS_GPIOS variable after NRF52. This functionality can be removed by using nrfjprog.exe with arguments --recover -f NRF52. Pins L24 and J24 are by default configured to use the NFC antenna, but if they are needed as normal GPIOs, R44 and R46 must be NC and R43 and R45 must be shorted by 0R. Figure 33: NFC input schematic 4440_025 v1.2 36 Hardware description 8.14 Extra op-amp The voltage follower for the power supply uses a dual package op-amp. The extra op-amp has been routed out to a connector (P28, not mounted) so that it is accessible for the user. For more information on the power supply, see section nRF52840 power source on page 21. Figure 34: Extra op-amp 8.15 Solder bridge configuration This complete overview of solder bridges on the nRF52840 Preview DK helps to change the default state. Solderbridge Default Function SB1 Closed Cut to disconnect the 32.768 kHz on P0.01 SB2 Closed Cut to disconnect the 32.768 kHz on P0.00 SB3 Open Short to enable P0.01 as normal GPIO SB4 Open Short to enable P0.00 as normal GPIO SB5 Closed Cut to disconnect LED1 SB6 Closed Cut to disconnect LED2 SB7 Closed Cut to disconnect LED3 SB8 Closed Cut to disconnect LED4 SB9 Open Short to bypass peripheral power switch SB10 Closed Cut to disconnect the QSPI memory from P0.23 SB11 Closed Cut to disconnect the QSPI memory from P0.19 SB12 Closed Cut to disconnect the QSPI memory from P0.20 SB13 Closed Cut to disconnect the QSPI memory from P0.17 SB14 Closed Cut to disconnect the QSPI memory from P0.21 SB15 Closed Cut to disconnect the QSPI memory from P0.22 SB16 Closed Cut to disconnect QSPI memory power supply from VDD_PER SB17 Open Short to connect QSPI memory power supply to VDD SB18 Open Short to connect QSPI memory power supply to VDD_nRF SB20 Open Short to enable P0.23 as a normal GPIO SB21 Open Short to enable P0.19 as a normal GPIO 4440_025 v1.2 37 Hardware description Solderbridge Default Function SB22 Open Short to enable P0.20 as a normal GPIO SB23 Open Short to enable P0.17 as a normal GPIO SB24 Open Short to enable P0.21 as a normal GPIO SB25 Open Short to enable P0.22 as a normal GPIO SB30 Open Short to reset the interface MCU SB31 Open Short to bypass the USB detect switch SB32 Open Short to permanently enable the I2C pull-up resistors SB33 Closed Cut to permanently disable the I2C pull-up resistors SB34 Open Short to bypass the power switch on the USB power SB35 Open Short to bypass the power switch on the coin cell battery power SB36 Open Short to bypass the power switch on the external supply power SB37 Open Short to bypass the interface MCU power switch SB38 Closed Cut to disable VDD power to the Arduino interface SB39 Open Short to bypass the power switch for regulator, coin cell, or external supply SB40 Closed Cut for current measurements of the VDD_nRF SB41 Closed Cut for current measurements of the VDD_nRF_HV SB42 Closed Cut to disconnect IF Boot/Reset button from nRF52840 reset pin when the interface MCU is disconnected SB43 Open Short to connect IF Boot/Reset button to RESET pin on the Arduino interface SB44 Open Short to connect the RESET pin on the Arduino interface to the nRF52840 reset pin SB45 Open Short to connect the RESET pin on the Arduino interface to the interface nRF52840 reset pin when the interface MCU is disconnected SB46 Open Short to connect the RESET pin on the Arduino interface to the interface MCU Boot when the interface MCU is disconnected SB47 Open Short to enable power supply of the external device when using the debug out connector SB48 Open Short to bypass the interface MCU USB power switch SB49 Open Short to connect VDD_UTMI to VDD_SAM SB50 Closed Cut to disconnect the nRF52840 CTS line from the signal switch and interface MCU SB51 Closed Cut to disconnect the nRF52840 RTS line from the signal switch and interface MCU SB52 Closed Cut to disconnect the nRF52840 RxD line from the signal switch and the interface MCU 4440_025 v1.2 38 Hardware description Solderbridge Default Function SB53 Closed Cut to disconnect the nRF52840 TxD line from the signal switch and interface MCU SB54 Closed Cut to disconnect the nRF52840 SWDIO line from the signal switch and interface MCU SB55 Closed Cut to disconnect the nRF52840 SWDCLK line from the signal switch and interface MCU SB56 Closed Cut to disconnect the nRF52840 RESET line from the signal switch and interface MCU SB57 Closed Cut to disconnect the nRF52840 SWO line from the signal switch and the interface MCU SB65 Closed Cut to disable the pull-up resistor of the IMCU_BOOT line SB80 Open Short to bypass the power switch for the VBUS of nRF52840 SB81 Open Short to bypass the power switch for VDD_HV of nRF52840 Table 9: Solder bridge configuration 4440_025 v1.2 39 Legal notices By using this documentation you agree to our terms and conditions of use. 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