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STWBC-EP

Pins functional description

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5.5

Input power supply management: VMAIN, QC_IO

The STWBC-EP monitors the input power supply voltage using the VMAIN pin. This voltage

is used for optimum programming of the DC-DC converter but also for the wireless power

mode of the operation.

The STWBC-EP is capable of requesting 12 V output voltage available from some USB wall

adaptors. While the USB wall adaptor provides 5 V by default, using a specific signaling on

the D+ and D- signals of the USB interface, 12 V can be obtained if supported. When 12 V is

available, the STWBC-EP can provide up to 15 W to a receiver load. The QC_IO pin has to

be connected to a simple interfacing circuit with the USB connector. When QC_IO is 0, 5 V

is requested to the USB wall adaptor. When QC_IO is 1, 12 V is requested to the USB wall

adaptor.

5.6

External digital interface: UART_TX, UART_RX

The STWBC-EP can be programmed and/or controlled using a 57600 bps 8-bit 1start 1stop

no-parity UART interface. The STWBC-EP UART TX output is present on the UART_TX pin

and the UART RX input is present on the UART_RX pin.

5.7

End user signaling: LED

The STWBC-EP manages 2 LEDs (red and green typically) using a single LED pin. The pin

is the output 0 to drive the first LED, the output 1 to drive the second LED and high

impedance to not drive any LED. A simple circuit can be used to interface the LEDs with this

LED pin.

5.8

Expansion interface: I2C_SDA, I2C_SCL

The STWBC-EP embeds an I²C master interface on the I2C_SDA and I2C_SCL pins. This

interface is typically inactive and reserved for future use.

5.9

Debug: SWIM, NRST

The SWIM pin may be used to interface with the STLINK/V2 debugger. The STWBC-EP can

be reset using the active-low NRST pin.