Emcraft Systems
For custom designs using the SOM-BSB-EXT schematics as a reference it is recommended to
include voltage suppressors such as Littelfuse’s PGB1010603M, onto the USB data lines
(USB_OTG_N, USB_OTG_P, USB_N, and USB_P) to improve a quality of the USB signals.
2.7. ARM JTAG Interface
The SOM-BSB-EXT provides the ARM JTAG interface on the P3 connector for debugging of
the STM32F4 MCU on the STM32F4 SOM.
The connector is a standard 20-pin JTAG port supported by standard Cortex-M4
programmers/emulators.
2.8. Power
The SOM-BSB-EXT receives the +5 V power from the P1 mini-USB connector. Additionally, it
is possible to supply an external +5 V power through the dedicated pad P10.2 of the SOM-
BSB-EXT breadboard area. Configuration of the +5 V input power supply is defined by the
JP3 header. The default settings of the JP3 are: 1-3 open, 2-4 closed. For further details on
the JP3 settings, see Section 4.
The +3.3 V supply voltage for the STM32F4 SOM and other components of the SOM-BSB-
EXT is derived from the +5 V input voltage using the TPS73733DCQ LDO regulator. The
regulator dissipates approximately 1 Watt and is mounted on a heatsink. The SOM-BSB-EXT
provides a green Power Good LED that indicates presence of the +3.3 V power on the output
of the LDO regulator.
It is possible to turn the LDO regulator off for debug purposes. To do so, the control signal
VCC3_EN (P10.6 pad of the SOM-BSB-EXT breadboard area) must be connected to the
ground.
2.9. Reset Button
The SOM-BSB-EXT provides the S1 reset button used to trigger a hardware reset of the SOM.
2.10. Reset LED
The Reset LED indicates the status of the nRESET_OUT signal of the SOM. The LED is lit when
nRESET_OUT is low.
2.11. User Button and User LED
The SOM-BSB-EXT provides the S2 user button and the DS4 user LED as a simple
input/output interface for testing and demonstration purposes.
For further details, refer to Sections 5 and 6.
2.12. Breadboard Area
All unused signal pins of the SOM are available on the breadboard area marked as P7-P14.
For further details, refer to Section 3.6.
3. Connectors
This section provides a full pin definition of all connectors available on the SOM-BSB-EXT.
3.1. SOM-BSB-EXT Connectors
Table 1 provides a summary of the SOM-BSB-EXT connectors:
STM32F4 SOM (System-On-Module) Baseboard 5/17 Version 1.1
Hardware Architecture December 19, 2013
