DocID027942 Rev 3 15/49
UM1907 Hardware layout and configuration
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1. If more than 500 mA current is needed by the board, the PC may be damaged or
current can be limited by the PC. As a consequence the board is not powered correctly.
2. 500 mA will be requested at the enumeration, so there is a risk that the request is
rejected and enumeration does not succeed if the PC cannot provide such current.
6.4 Clock sources
Up to 3 clock sources as described below:
• X1, 24 MHz oscillator for the USB OTG HS PHY and camera module (daughterboard)
• X2, 25 MHz oscillator for the STM32F746NGH6 microcontroller and Ethernet PHY
• X3, 32 KHz crystal for the STM32F746NGH6 embedded RTC
6.5 Reset sources
The reset signal of STM32F746G-DISCO discovery board is active low and the reset
sources include:
• Reset button B2
• Arduino Uno shield board from CN6
• Embedded ST-LINK/V2-1
6.6 Audio
An audio codec WM8994ECS/R from CIRRUS with 4 DACs and 2ADCs is connected to SAI
interface of STM32F746NGH6. It communicates with STM32F746NGH6 via I
2
C bus shared
with the camera module and I
2
C extension connector.
• The analog line input is connected to ADC of WM8994ECS/R through blue audio jack
CN11.
• The analog line output is connected to DAC of WM8994ECS/R via green audio jack
CN10.
• Two external speakers can be connected to WM8994ECS/R via JP3 for right speaker
and JP4 for left speaker.
• Two digital microphones (ST MEMs microphone) MP34DT01TR are on the
STM32F746G-DISCO discovery board. They are connected to the input digital
microphones of WM8994ECS/R.
• One coaxial connector CN1 is implemented on STM32F746G-DISCO to receive
external audio data compatible with SPDIF specification.
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