USB¶

The QS Computer-on-Modules, such as QSMP and QS8M, contain two separate USB 2.0 compliant interfaces. High-speed USB operates at 480 Mb/s observing some basic rules or guidelines will usually guarantee successful operation.

VBUS¶

The QS modules does not include a signal for supplying the 5V VBUS power for USB. An external power management chip or discrete logic for enabling VBUS is required for the host operation. The power distribution circuit must have over-current detection capability to be compliant with the USB standard. There are no dedicated pins reserved for this in the QS standard. Use General Purpose Input/Output (GPIO) pads as OE (VBUS_EN) and OC (VBUS_OC) for the VBUS power distribution circuit. Some QS modules have pins with dedicated VBUS_EN (Output) and VBUS_OC (Input) alternate functions, e.g. QS8M pin 71 - USB1_OTG_PWR and pin 72 USB1_OTG_OC. Using these may interfere with the use other standard QS interfaces. A switch designed specifically for USB power, such as the Maxim MAX1931, or a general purpose power-distribution chip, such as Micrel’s MIC2026, can be used.

Note

The i.MX8M Nano processor has only one integrated port.

Pin	Signal	type	I/O	Requirements
43	USB_VBUS_A	5V	IN	Can be connected to VBUS directly
44	USB_DN_A	USB	I/O	Route USB differential signals with 90 Ω differential impedance
45	USB_DP_A	USB	I/O
46	USB_VBUS_B	5V	IN	Can be connected to VBUS directly
47	USB_DN_B	USB	I/O	Route USB differential signals with 90 Ω differential impedance
48	USB_DP_B	USB	I/O

Wiring example¶

USB2.0 Design Recommendations

Parameter	MIN	TYP	MAX
Operating Speed			240 MHz
Signal Trace Length			15 cm
Differential Pair Skew			5 ps
Differential Trace Impedance	81 Ω	90 Ω	99 Ω

USB3 Super Speed¶

The QSXP provides a complete USB3.0 interface. To implement a USB Type-C interface (UFP, DFP, or DRP), external hardware must be added to manage the two configuration channel IOs (CC1 and CC2) as well as monitor the plug orientation and switch the single USB3 SS interface.

Route all USB differential signals with 90 Ω differential impedance.

Pin	Signal	Requirements
25A	USB_TXN
26A	USB_TXP
50A	USB_RXN
51A	USB_RXP

USB3 Super Speed Design Recommendations

Parameter	MIN	TYP	MAX
Operating Speed			2.5 GHz
Signal Trace Length			10 cm
Differential Pair Skew			1 ps
RX/TX Skew			1.6 ns
Differential Trace Impedance	85 Ω	90 Ω	95 Ω

Pins	Function	Pins	Function	Pins	Function	Pins	Function
1-4	SPI	5-10	I2C	11-14	CAN	15-18	SAI
19-35	Ethernet	36-42	SD Interface	43-48	USB	49-52	Power Supply, Reset and Boot mode
53-76	18-bit RGB Display Interface	77-78	Backlight and Display Control	53-72	Camera	79-88	MIPI DSI Display
89-96	UART	97-100	SPI	1A,75A,76A,100A	PCIe	25A,26A,50A,51A	USB3 Super Speed