UM1956 Rev 5 19/37
UM1956 Hardware layout and configuration
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6.7 JP1 (IDD)
JP1, labeled IDD, is used to measure the STM32 microcontroller consumption by removing
the jumper and connecting an ammeter:
• JP1 on: STM32 is powered (default)
• JP1 off: an ammeter must be connected to measure the STM32 current
If there is no ammeter, STM32 is not powered.
6.8 OSC clock
U2 pin 2 and pin 3 can be used as OSC clock input or as Arduino Nano D8 and D7 GPIO.
There are four ways to configure the pins corresponding to different STM32 and clock usage
(refer to Table 6).
Table 6. OSC clock configurations
Solder bridge
STM32 Clock configuration
SB4 SB17 SB6 SB8
SB5 and
SB7
ON OFF OFF ON OFF
STM32Fxxx
MCO from ST-LINK
co
nnected to OSCIN
(PF0)
(1)
1. In applications where VCP is used for communication at a speed higher than 9600 bauds, it may be
needed to use this solder bridge configuration, to use 8 MHz clock (MCO from ST-LINK) and get a more
pre
cise frequency.
OFF OFF ON ON OFF
HSI configuration
(d
efault configuration)
OFF ON OFF OFF OFF
STM32Lxxx
MCO from ST-LINK
co
nnected to CKIN
(PA0)
(1)
OFF OFF OFF OFF ON
32K LSE mounted on X1
(d
efault configuration)
OFF OFF ON ON/OFF OFF
All
Arduino Nano D7
co
nnected to PF0 / PC14
OFF OFF ON/OFF ON OFF
Arduino Nano D8
co
nnected to PF1 / PC15
Boards with STM32Lxxx are delivered with 32.768 KHz crystal (X1). Associated capacitors
and solder bridges (C12, C13 and SB4 to SB8) are configured to support LSE by default.
Boards with STM32Fxxx are delivered without crystal (X1). Associated capacitors (C12,
C13
) are not populated and SB4 to SB8 are configured to support HSI by default.
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