STMicroelectronics STM32L476 User manual

June 2018 UM1879 Rev 4 1/41
1
UM1879
User manual
Discovery kit with STM32L476VG MCU
Introduction
The STM32L476 Discovery kit (32L476GDISCOVERY) helps the user to discover the
STM32L4 ultra-low-power features and to develop and share applications.
It is based on the STM32L476VGT6 microcontroller with three I2Cs, three SPIs, six
USARTs, CAN, SWPMI, two SAIs, 12-bit ADCs, 12-bit DAC, LCD driver, internal 128 Kbytes
of SRAM and 1 Mbyte of Flash memory, Quad-SPI, touch sensing, USB OTG FS, LCD
controller, FMC, JTAG debugging support.
The 32L476GDISCOVERY includes an ST-LINK/V2-1 embedded debugging tool interface,
LCD (24 segments, 4 commons), LEDs, push-button, joystick, USB OTG FS, audio DAC,
MEMS (microphone, 3-axis gyroscope, 6-axis compass), Quad-SPI Flash memory,
embedded ammeter measuring STM32 consumption in low-power mode.
External boards can be connected through the extension and probing connectors.
Figure 1. STM32L476 Discovery board
Picture is not contractual.
www.st.com

Contents UM1879
2/41 UM1879 Rev 4
Contents
1 Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2 Product marking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3 System requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4 Development toolchains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5 Demonstration software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
6 Ordering information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
7 Delivery recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
8 Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
9 Bootloader limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
10 Hardware layout and configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
10.1 Embedded ST-LINK/V2-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
10.1.1 Drivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
10.1.2 ST-LINK/V2-1 firmware upgrade . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
10.1.3 Using ST-LINK/V2-1 to program/debug the STM32L476VGT6
on board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
10.1.4 Using ST-LINK/V2-1 to program/debug an external STM32 application
board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
10.2 Power supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
10.3 Clock source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
10.4 Reset source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
10.5 User interface: LCD, joystick, LEDs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
10.6 Boot0 configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
10.7 Quad-SPI NOR Flash memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
10.8 USB OTG FS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
10.9 USART configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
10.10 Audio DAC and MEMS microphone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

UM1879 Rev 4 3/41
UM1879 Contents
3
10.11 9-axis motion sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
10.12 I2C extension connector CN2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
10.13 MCU current ammeter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
10.14 Extension connector P1 and P2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
10.15 Solder bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
11 Schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Appendix A Power consumption measurements . . . . . . . . . . . . . . . . . . . . . . . . 35
Appendix B Mechanical drawing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Appendix C Compliance statements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
C.1 FCC Compliance Statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
C.1.1 Part 15.19 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
C.1.2 Part 15.105 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
C.1.3 Part 15.21 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
C.2 IC Compliance Statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
C.2.1 Compliance Statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
C.2.2 Déclaration de conformité. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

List of tables UM1879
4/41 UM1879 Rev 4
List of tables
Table 1. Ordering information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Table 2. ON/OFF conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Table 3. Jumper states . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Table 4. Debug connector CN4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Table 5. Reset related jumper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Table 6. Connector CN2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Table 7. Extension connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Table 8. Solder bridges. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Table 9. Typical power consumption of the STM32L476 Discovery board. . . . . . . . . . . . . . . . . . . . 36
Table 10. Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

UM1879 Rev 4 5/41
UM1879 List of figures
5
List of figures
Figure 1. STM32L476 Discovery board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Figure 2. Hardware block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Figure 3. STM32L476 Discovery board top layout. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Figure 4. STM32L476 Discovery board bottom layout. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Figure 5. Updating the list of drivers in device manager . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Figure 6. CN1, CN3 (ON), CN4 connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Figure 7. CN1, CN3 (OFF), CN4 connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Figure 8. Board jumper location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Figure 9. Connector CN2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Figure 10. STM32L476 Discovery board design top sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Figure 11. ST-LINK/V2-1 with support of SWD only . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Figure 12. STM32L476VGT6 MCU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Figure 13. IDD measurement / MFX (Multi Function eXpander) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Figure 14. Joystick ACP, LEDs and push-button. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Figure 15. LCD display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Figure 16. OTG USB FS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Figure 17. Audio DAC and microphone MEMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Figure 18. Quad-SPI Flash memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Figure 19. Gyroscope, accelerometer, magnetometer MEMS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Figure 20. Power consumption tree . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Figure 21. STM32L476 Discovery board mechanical drawing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Features UM1879
6/41 UM1879 Rev 4
1 Features
•STM32L476VGT6 microcontroller featuring 1 Mbyte of Flash memory and 128 Kbytes
of RAM in LQFP100 package
•On-board ST-LINK/V2-1 supporting USB reenumeration capability
•Three different interfaces supported on USB:
– Virtual Com Port
– Mass storage
– Debug port
•Arm®Mbed enabled™(a) (see http: //mbed.org)
•LCD 24 segments, 4 commons in DIP 28 package
•Seven LEDs:
– LD1 (red/green) for ST-LINK/V2-1 USB communication
– LD2 (red) for 3.3 V power on
– LD3 overcurrent (red)
– LD4 (red), LD5 (green) two user LEDs
– LD6 (green), LD7 (red) USB OTG FS LEDs
•Push-button (reset)
•Four-direction joystick with selection
•USB OTG FS with Micro-AB connector
•SAI Audio DAC, stereo with output jack
•Digital microphone MEMS
•Accelerometer and magnetometer MEMS
•Gyroscope MEMS
•128-Mbit Quad-SPI Flash memory
•STM32 current ammeter with 4 ranges and auto calibration
•I2C extension connector for external board
•Four power supply options:
–ST-LINK/V2-1
– USB FS connector
– External 5V
– CR2032 battery (not provided)
•Extension connectors
•Comprehensive free software including a variety of examples, part of STM32Cube™
package
a. Arm and Mbed are registered trademarks or trademarks of Arm Limited (or its subsidiaries) in the US and/or
elsewhere.

UM1879 Rev 4 7/41
UM1879 Product marking
40
2 Product marking
Evaluation tools marked as “ES” or “E” are not yet qualified and are therefore not ready to
be used as reference design or in production. Any consequences arising from such usage
will not be at STMicroelectronics’ charge. In no event will STMicroelectronics be liable for
any customer usage of these engineering sample tools as reference designs or in
production.
‘E’ or ‘ES’ marking examples of location:
•on the targeted STM32 that is soldered on the board (for illustration of STM32 marking,
refer to the section Package information in the STM32 datasheet at www.st.com).
•next to the evaluation tool ordering part number, that is stuck or silkscreen printed on
the board
This board features a specific STM32 device version, which allows the operation of any
bundled commercial stack/library available. This STM32 device shows a "U" marking option
at the end of the standard part number and is not available for sales.
In order to use the same commercial stack in his application, a developer may need to
purchase a part number specific to this stack/library. The price of those part numbers
includes the stack/library royalties.
3 System requirements
•Windows®OS (7, 8 and 10), Linux®64-bit or macOS®(a)
•USB Type-A to Micro-B cable
4 Development toolchains
•Keil®MDK-ARM(b)
•IAR™ EWARM(b)
•GCC-based IDEs including free SW4STM32 from AC6
•Arm®Mbed™ online (see http://mbed.org)
a. macOS® is a trademark of Apple Inc., registered in the U.S. and other countries.
b. On Windows only

Demonstration software UM1879
8/41 UM1879 Rev 4
5 Demonstration software
The demonstration software, included in the STM32Cube MCU Package corresponding to
the on-board MCU, is preloaded in the STM32 Flash memory for easy demonstration of the
device peripherals in standalone mode. The latest versions of the demonstration source
code and associated documentation can be downloaded from the www.st.com/stm32l4-
discovery web page.
6 Ordering information
To order the 32L476GDISCOVERY Discovery kit, refer to Table 1.
7 Delivery recommendations
Some verifications are needed before using the board for the first time to make sure that
nothing has been damaged during the shipment and that no components are unplugged or
lost. When the board is extracted from its plastic bag, check that no component remains in
the bag. In particularly, make sure that the following jumpers on top side of the board are
plugged: CN3, JP3, JP5, and JP6.
The battery CR2032 is not provided.
8 Conventions
Table 2 provides conventions used in the present document.
Table 1. Ordering information
Order code Target STM32
32L476GDISCOVERY STM32L476VGT6
Table 2. ON/OFF conventions
Convention Definition
Jumper JPx ON Jumper fitted
Jumper JPx OFF Jumper not fitted
Solder bridge SBx ON SBx connections closed by solder
Solder bridge SBx OFF SBx connections left opened

UM1879 Rev 4 9/41
UM1879 Bootloader limitations
40
9 Bootloader limitations
Boot from system Flash memory results in executing bootloader code stored in the system
Flash memory protected against writing and erasing. This allows in-system programming
(ISP), that is, flashing the STM32 user Flash memory. It also allows writing data into RAM.
The data come in via one of communication interfaces such as USART, SPI, I2C bus, USB
or CAN.
Bootloader version can be identified by reading the Bootloader ID at the address
0x1FFF6FFE.
The STM32L476VGT6 part soldered on the 32L476GDISCOVERY main board is marked
with a date code corresponding to its date of manufacturing. STM32L476VGT6 parts with
the date code prior or equal to week 22 of 2015 are fitted with bootloader V 9.0 affected by
the limitations to be worked around, as described hereunder. Parts with the date code
starting from week 23 of 2015 contain bootloader V 9.2 in which the limitations no longer
exist.
To locate the visual date code information on the STM32L476VGT6 package, refer to its
datasheet (DS10198) available at www.st.com, section Package Information. Date code
related portion of the package marking takes Y WW format, where Y is the last digit of the
year and WW is the week. For example, a part manufactured in week 23 of 2015 bares the
date code 5 23.
Bootloader ID of the bootloader V 9.0 is 0x90.
The following limitations exist in the bootloader V 9.0:
1. RAM data get corrupted when written via USART/SPI/I2C/USB interface
Description:
Data write operation into RAM space via USART, SPI, I2C bus or USB results in wrong
or no data written.
Workaround:
To correct the issue of wrong write into RAM, download the STSW-STM32158
bootloader V 9.0 patch package from the www.st.com website and load "Bootloader
V9.0 SRAM patch" to the MCU, following the information in readme.txt file available in
the package.
2. User Flash memory data get corrupted when written via CAN interface
Description:
Data write operation into user Flash memory space via CAN interface results in wrong
or no data written.
Workaround:
To correct the issue of wrong write into Flash memory, download the STSW-STM32158
bootloader V 0.9 patch package from the www.st.com website and load "Bootloader V9.0
CAN patch" to the MCU, following the information in readme.txt file available in the package.

Hardware layout and configuration UM1879
10/41 UM1879 Rev 4
10 Hardware layout and configuration
The STM32L476 Discovery board is designed around the STM32L476VGT6 (100-pin LQFP
package). The hardware block diagram (see Figure 2) illustrates the connection between
the STM32L476VGT6 and the peripherals (9-axis motion sensors, digital microphone
MEMS, LCD segment, 128 Mbytes of Quad-SPI Flash memory, SAI Audio DAC stereo with
3.5mm output jack, USB OTG FS, IDD current measurement, LEDs, push-button, joystick)
and the Figure 3 will help to locate these features on the STM32L476 Discovery board.
Figure 2. Hardware block diagram
A to Mini-B
USB
Embedded
ST_LINK/V2-1
(3V CR2032 Battery)
CR1
SWDHeader P1
Header P2
STM32L476VGT6
power
JP6
IO
IO reset
9-axis motion
sensors
digital
microphone
MEMS
SAI Audio DAC
stereo
LCD segment
(4x24)
128Mb
QuadSPI flash
USB OTG FS with
Micro-A-B
connector
IDD current
measurement
Reset
pushbutton
Joystick with
4-direction
control and
selector
User LEDs
LD5 (green)
LD4 (red)
IO

UM1879 Rev 4 11/41
UM1879 Hardware layout and configuration
40
Figure 3. STM32L476 Discovery board top layout
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Hardware layout and configuration UM1879
12/41 UM1879 Rev 4
Figure 4. STM32L476 Discovery board bottom layout
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UM1879 Rev 4 13/41
UM1879 Hardware layout and configuration
40
10.1 Embedded ST-LINK/V2-1
The ST-LINK/V2-1 programming and debugging tool is integrated on the STM32L476
Discovery board. Compared to ST-LINK/V2 the changes are listed below.
The new features supported on ST-LINK/V2-1 are:
•USB software re-enumeration
•Virtual Com Port interface on USB
•Mass storage interface on USB
•USB power management request for more than 100mA power on USB
These features are no more supported on ST-LINK/V2-1:
•SWIM interface
•Application voltage lower than 3 V
For all general information concerning debugging and programming features common
between V2 and V2-1 refer to ST-LINK/V2 in-circuit debugger/programmer for STM8 and
STM32 User manual (UM1075).
There are two different ways to use the embedded ST-LINK/V2-1 depending on the jumper
states:
•Program/debug the STM32L476VGT6 on board (Section 10.1.3)
•Program/debug an STM32 in an external application board using a cable connected to
SWD connector CN4 (Section 10.1.4)
.
10.1.1 Drivers
The ST-LINK/V2-1 requires a dedicated USB driver, which can be found on the www.st.com
website.
In case the STM32L476 Discovery board is connected to the PC before the driver is
installed, some interfaces may be declared as “Unknown” in the PC device manager. In this
case the user must install the driver files, and update the driver of the connected device
from the device manager.
Table 3. Jumper states
Jumper state Description
Both CN3 jumpers ON ST-LINK/V2-1 functions enabled for on-board programming (default)
Both CN3 jumpers OFF ST-LINK/V2-1 functions enabled for external board through external
CN4 connector (SWD supported)

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Figure 5. Updating the list of drivers in device manager
1. Prefer using the “USB Composite Device” handle for a full recovery.
10.1.2 ST-LINK/V2-1 firmware upgrade
The ST-LINK/V2-1 embeds a firmware upgrade mechanism for in-situ upgrade through the
USB port. As the firmware may evolve during the life time of the ST-LINK/V2-1 product (for
example a new functionality, bug fixes, support for new microcontroller families), it is
recommended to visit the www.st.com website before starting to use the STM32L476
Discovery board and periodically, in order to stay up-to-date with the latest firmware version.
10.1.3 Using ST-LINK/V2-1 to program/debug the STM32L476VGT6
on board
To program the STM32L476VGT6 on board, simply plug in the two jumpers on CN3, as
shown in
Figure 6 in red, and connect the STM32L476 Discovery board to the PC through
the Mini-B USB ST-LINK/V2-1 CN1 connector.
Make sure the jumpers JP3, JP6.3V3, and JP5.ON are set.
Do not use the CN4 connector.
Figure 6. CN1, CN3 (ON), CN4 connections

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10.1.4 Using ST-LINK/V2-1 to program/debug an external STM32 application
board
To use the ST-LINK/V2-1 to program the STM32 on an external application board (out of the
STM32L476VGT6 on board), remove the two jumpers from CN3 as shown in Figure 7 in
red, and connect the board to the CN4 software debug connector according to Table 4.
Make sure the jumpers JP6.3V3, and JP5.OFF are set.
JP3, must be ON if CN4 pin 5 (NRST) is used in the external application board.
Figure 7. CN1, CN3 (OFF), CN4 connections
Table 4. Debug connector CN4
Pin CN4 Designation
1 Vapp VDD from application
2 SWLCK SWD clock
3 GND Ground
4 SWDIO SWD data input/output
5 NRST RESET of target MCU
6SWO Reserved

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10.2 Power supply
The power supply is provided with four options:
– ST-LINK/V2-1: CN1
– CR2032 battery (not provided): CR1
– External 5V: 5V_I
– USB FS connector: USB USER CN7
•ST-LINK/V2-1:
JP6 needs to be placed in position 3V3. JP3 is closed. JP5 is in position ON. CN3
jumpers are ON.
The STM32L476G Discovery board can be powered from the ST-LINK USB connector
CN1 (5V_USB_ST_LINK). Only the ST-LINK circuit has the power before the USB
enumeration, as the host PC only provides 100mA to the board at that time.
During the USB enumeration, the STM32L476 Discovery board requires 300 mA of
current to the host PC. If the host is able to provide the required power, the
STM32L476 is powered and the red LED LD2 is turned ON, thus the STM32L476
Discovery board and its extension board can consume no more than 300 mA current. If
the host is not able to provide the required current, the STM32L476 and the extension
board are not power supplied. As a consequence the red LED LD2 remains turned
OFF. In such case it is mandatory to use an external power supply, as explained in the
next section.
Warning: If the maximum current consumption of the STM32L476
Discovery board and its extension board exceeds 300 mA, it
is mandatory to power the STM32L476 Discovery board using
an external power supply connected to 5V_I.
Note: In case this board is powered by a USB charger or a USB battery connected on CN1, there
is no USB enumeration, the led LD2 remains OFF and the STM32L476 is not powered. In
this specific case only, fit the jumper JP2 to allow the STM32L476 to be powered anyway.
Remove this jumper JP2 if then a host PC is connected to the ST-LINK/V2-1 CN1 connector
to supply the board.
•CR2032 battery inserted in CR1 (bottom side):
– The CR2032 battery is not provided
– JP6 needs to be placed in position BATT. JP3 is opened. JP5 is in position ON
– The battery supplies the 3V3 and 3V power domains on board. All the peripherals
are powered, except the ST-LINK, which can only be supplied through the USB
connector CN1
•External 5V_I or USB USER CN7 (USB FS connector):
– External 5V_I: The pin 3 5V_I of P2 header can be used as input for an external
power supply. In this case, the STM32L476 Discovery board must be powered by
a power supply unit or by an auxiliary equipment complying with the standard EN-
60950-1: 2006+A11/2009, and must be Safety Extra Low Voltage (SELV) with a
limited power capability.
– To use the USB USER CN7 to power supply the board, a jumper needs to be
placed between VUSB pin 4 and the pin 3 5V_I of P2 header (see Figure 8).

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Figure 8. Board jumper location
In this condition it is still possible to use the USB ST-LINK for communication, for
programming or debugging, but it is mandatory to power supply the board first using
5V_I or USB USER CN7 then connect the USB ST-LINK cable to the PC. Proceeding
this way ensures that the enumeration occurs thanks to the external power source.
The following power sequence procedure must be respected:
1. Connect the external power source to 5V_I or USB USER CN7.
2. Power on the external power supply 5V_I or USB USER CN7.
3. Check that LD2 is turned ON.
4. Connect the PC to USB ST-LINK connector CN1.
If this order is not respected, the board may be supplied by 5V_USB_ST_LINK first
then by 5V_I or USB USER CN7 and the following risks may be encountered:
1. If more than 300 mA current is needed by the board, the PC may be damaged or the
current supply can be limited by the PC. As a consequence the board is not powered
correctly.
2. 300 mA is requested at enumeration (since JP2 must be OFF) so there is risk that the
request is rejected and the enumeration does not succeed if the PC cannot provide
such current. Consequently the board is not power supplied (LED LD2 remains OFF).
Note: The headers pins 5V (except in battery mode), 3V3, 2V5, 3V can be used as output power
supply when an extension board is connected to the P1 and P2 headers. The power
consumption of the extension board must be lower than 100 mA.

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10.3 Clock source
The STM32L476VGT6 MCU uses:
•A 32.768 KHz low-speed source:
– By default, the X3 crystal on board
– From an external oscillator through P2 header (pin 7 labeled ‘PC14’). The
configuration needed is:
SB19 opened, SB20 closed, R26 removed
•A system clock source:
– By default, generated by an internal STM32L476VGT6 oscillator. The
configuration needed is:
SB18 opened, SB21 and SB22 closed
– Or driven by an X2 Crystal on board (not fitted). The configuration needed is:
SB18, SB21 and SB22 opened
X2, R88, R89, C77, C78 fitted
– Or driven by a MCO signal (8MHz) from the ST-LINK MCU STM32F103CBT6
(U3).The configuration needed is:
SB18 closed, SB22 opened
R89 not fitted
– Or driven externally from PH0 through the P2 header, pin 9 labeled ‘PH0’.The
configuration needed is:
SB22 closed, SB18 opened
R89 not fitted
Note: Refer to Oscillator design guide for STM8S, STM8A and STM32 microcontrollers
Application note (AN2867).
10.4 Reset source
The reset signal NRST of the STM32L476 Discovery board is low active and the reset
sources include:
•The reset button B1, connected by default to NRST (SB23 closed)
•The embedded ST-LINK/V2-1
•The external reset pin 11 of P2 header connector, labeled ‘NRST’
•The external reset from SWD connector CN4, pin 5
Table 5. Reset related jumper
Jumper Description
JP3
When JP3 is closed, the SWD connector CN4 pin 5 and the embedded
ST-LINK/V2-1 are connected to NRST.
Default Setting: closed
JP3 is opened, no connection between CN4 and ST-LINK/V2-1 to
NRST. This must be used when the ST-LINK/V2-1 is not powered (i.e
STM32L476 Discovery board) is powered by the CR2032 battery

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10.5 User interface: LCD, joystick, LEDs
The STM32L476 Discovery board features sept LEDs with the following functionalities:
•LD1 COM: LD1 default status is red. LD1 turns to green to indicate that
communications are in progress between the PC and the ST-LINK/V2-1
•LD2 PWR: the red LED indicates that the board is powered
•LD3 OC: the red LED indicates a fault when the board is in current limit (510 mA)
•LD4 user: the red LED is a user LED connected to the I/O PB2 of the
STM32L476VGT6
•LD5 user: the green LED is a user LED connected to the I/O PE8 of the
STM32L476VGT6
•LD6, LD7: USB OTG FS LEDs, see Section 10.8
Four-direction joystick (B2) with selection and a reset push-button (B1) are available as
input devices.
An LCD 4x24 segments, 4 commons, multiplexed 1/4 duty, 1/3 bias is mounted on the
DIP28 connector U5.
10.6 Boot0 configuration
Boot0 is by default grounded through a pull-down R91.
It is possible to set Boot0 high, removing R91 and putting a jumper between P1 header
pin 6 BOOT0 and pin 5 3V.
10.7 Quad-SPI NOR Flash memory
128-Mbit Quad-SPI NOR Flash memory is connected to Quad-SPI interface of
STM32L476VGT6.
10.8 USB OTG FS
The STM32L476 Discovery board supports USB OTG Full Speed communication via a USB
Micro-AB connector (CN7) and a USB power switch (U14) connected to VBUS. The board
can be powered by this USB connection as described in Section 10.2.
A green LED LD6 will be lit in one of these cases:
•The power switch (U14) is ON and STM32L476 Discovery board works as a USB host
•VBUS is powered by another USB host when STM32L476 Discovery board works as a
USB device
Red LED LD7 will be lit when an overcurrent occurs.
In order to connect the OTG_FS_VBUS and OTG_FS_ID signals from the connector CN7 to
the OTG FS hardware IP of STM32L476VGT6, remove the LCD from its socket U5, and
close SB24 and SB25.
The default configuration is: the LCD is connected to U5, and SB24 and SB25 are opened.
In this case the OTG_FS_VBUS and OTG_FS_ID signals from CN7 are connected to the
OTG FS peripheral of the STM32L476VGT6 available on PC11 and PC12.

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10.9 USART configuration
The USART interface available on PD5 and PD6 of the STM32L476VGT6 can be
connected to the ST-LINK MCU to use the Virtual Com Port function.
To use the Virtual Com Port function with:
•The on-board STM32L476VGT6: set SB13 and SB16 ON (SB15, SB17 must be OFF).
•An external MCU: remove solder from SB13 and SB16, solder a two pins header on
JP4, then RX and TX of the external MCU can be connected directly to RX and TX of
JP4.
(For more details see Section 11: Schematics)
10.10 Audio DAC and MEMS microphone
An audio stereo DAC CS43L22 (U13) is connected to SAI interface of STM32L476VGT6.
The STM32L476VGT6 controls the audio DAC via the I2C1 bus which is shared with the I2C
extension connector CN2.
I2C1 is also available on the connector P1, pins labeled ‘PB6’ (I2C1_SCL) and ‘PB7’
(I2C1_SDA).
The stereo output jack connector is CN6.
Note: I2Caddress of CS43L22 is 0x94.
A MEMS audio sensor omnidirectional digital microphone provides a digital signal in PDM
format to the STM32L476VGT6.
10.11 9-axis motion sensors
STM32L476 Discovery board supports some 9-axis motion sensors, composed of:
•L3GD20 (U7): a three-axis digital output gyroscope
•LSM303C (U6): a 3D accelerometer and 3D magnetometer module
which are connected to STM32L476VGT6 through SPI.
10.12 I2C extension connector CN2
Figure 9. Connector CN2
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