USB-A Port

On the left end of the FeatherWing is the USB type A port for connecting USB devices to. This USB-A port can be used for sending or receiving data from an attached USB device with the MAX3421E.

MAX3421E Control Pins

The MAX3421E USB Host chip on the FeatherWing uses SPI plus an IRQ pin to send data to just about any USB device.

• MOSI - This is the SPI MOSI (Microcontroller Out / Serial In) pin.
• MISO - This is the SPI MISO (Microcontroller In Serial Out) pin.
• SCK - This is the SPI clock input pin.
• CS - This is the chip select pin. It is connected to pin 10 on the FeatherWing. It is also broken out towards the middle of the board.
• IRQ - This is the interrupt pin for the MAX3421E. It is connected to pin 9 on the FeatherWing and is broken out towards the middle of the board.

GPX Pin

• GPX - Towards the center of the FeatherWing is the general purpose multiplexed push-pull output pin for the MAX3421E. This is for advanced users. The internal MAX3421E signal that appears on GPX is programmable by writing to the GPXB and GPXA bits of the PINCTL (R17) register and the SEPIRQ bit of the MODE (R27) register.

GPX indicates one of five signals:

1. OPERATE: This signal goes high when the MAX3421E is able to operate after a power-up or RES reset. OPERATE is active when the RES input is high and the internal power-on-reset (POR) is not asserted. OPERATE is the default GPX output.
2. VBUS_DET: VBUS_DET is the VBCOMP comparator output. This allows the user to directly monitor the VBUS status.
3. BUSACT: USB BUS activity signal (active high). This signal is active whenever there is traffic on the USB bus. The BUSACT signal is set whenever a SYNC field is detected. BUSACT goes low during bus reset or after 32-bit times of J-state.
4. INIRQ: When the SEPIRQ bit of the MODE (R27) register is set high, the BUSACT signal is removed from the INT output and GPX is used as an IRQ output pin dedicated to GPIN interrupts if GPX[B:A] = 10. In this mode, GPIN interrupts appear only on the GPX pin, and do not appear on the INT output pin.
5. SOF: A square wave with a positive edge that indicates the USB start-of-frame.

5V Enable Pin and Jumper

• 5V - Towards the middle of the FeatherWing is a pin labeled 5V. This is the 5V enable output from the 5V 1A booster. If you tie this pin to ground, it can disable 5V power to the USB-A port, effectively turning off your connected USB device.
• 5V Enable Jumper - On the back of the FeatherWing is an open jumper. If you solder this jumper closed you will connect the 5V enable pin to GPOUT0 (general purpose output 0) on the MAX3421E. This output is controllable over SPI, which means you can then enable or disable 5V to the USB-A port in software.

5V LED

• 5V LED - Towards the right end of the FeatherWing is a green LED labeled 5V on the FeatherWing silk. It indicates whether the 5V power from the 5V 1A booster is enabled.

Reset Button 

• RST - The reset button, located in the top left corner on the FeatherWing, is connected to the reset pin.