Hardware layout and configuration UM1956
18/31 DocID028406 Rev 1
6.5 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 STM32 current.
If there is no ammeter, STM32 is not powered.
6.6 OSC clock
U2 pin 2 and pin 3 can be used as OSC clock input or can be used as Arduino Nano D8 and
D7 GPIO. There are four ways to configure the pins corresponding to different STM32
MCUs and clock usage (refer to Table 5).
Boards with STM32Lxxx are delivered with 32.768 KHz crystal (X1). Associated capacitors
and solder bridges (C12, C13, 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.
6.7 USART virtual communication
Thanks to SB2 and SB3, the USART interface of STM32 available on PA2 (TX) and PA15
(RX), can be connected to ST-LINK/V2-1. When USART is not used it is possible to use PA2
as Arduino Nano A7. Refer to Table 6.
Table 5. 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
connected to OSCIN
(PF0)
(1)
1. In applications, where VCP is used for communication at speed higher than 9600 bauds, it may be needed
to use this solder bridge configuration, to use 8MHz clock (MCO from ST-LINK) to get a more precise
frequency.
OFF OFF ON ON OFF
HSI configuration
(default configuration)
OFF ON OFF OFF OFF
STM32Lxxx
MCO from ST-LINK
connected to CKIN
(PA0)
(1)
OFF OFF OFF OFF ON
32K LSE mounted on X1
(default configuration)
OFF OFF ON ON/OFF OFF
All
Arduino Nano D7
connected to PF0 / PC14
OFF OFF ON/OFF ON OFF
Arduino Nano D8
connected to PF1 / PC15
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