U.2

The U.2 connector is a 68-pin SFF-8639 connector on the short edge of the board, opposite the DC jack. It carries interfaces for expansion boards:

• Two SATA 3.0 channels, SATA0 and SATA2. The SATA2 lanes can carry PCIe 2.0 instead.
• An RGMII interface to the second Ethernet controller, GMAC0, for an external Ethernet PHY
• A USB 2.0 port
• I²C3
• 5 V, up to 3 A

Figure 1. The U.2 connector

The U.2 connector is intended for custom expansion boards. Using its interfaces needs support in the operating system. For the status in Mixtile OS, see Hardware Interfaces in Mixtile OS.

The SATA power connector, on the opposite short edge next to the DC jack, supplies a SATA drive attached through the U.2 connector, and can also power the board, see Power Supply.

Pin Assignments

Pin#	PinName	PinType	Input/Output	Signal Description
1	GND	GND	NA	Power and signal reference ground
2	SATA0_SSRXP	LVDS	Input	SATA data signal input Positive
3	SATA0_SSRXN	LVDS	Input	SATA data signal input Negative
4	GND	GND	NA	Power and signal reference ground
5	SATA0_SSTXN	LVDS	Output	SATA data signal output Negative
6	SATA0_SSTXP	LVDS	Output	SATA data signal output Positive
7	GND	GND	NA	Power and signal reference ground
8	GMAC0_TXEN	IO	Output	RGMII signal
9	GMAC0_RXD2	IO	Input	RGMII signal
10	NC	NA	NA	Not connected to this pin
11	GMAC0_RXD3	IO	Input	RGMII signal
12	GMAC0_RXD0	IO	Input	RGMII signal
13	GMAC0_RXD1	IO	Input	RGMII signal
14	NC	NA	NA	Not connected to this pin
15	I2C3_SCL_M0	IO	Output	I2C clock signal
16	I2C3_SDA_M0	IO	I/O	I2C data signal
17	GND	GND	NA	Power and signal reference ground
18	GND	GND	NA	Power and signal reference ground
19	GND	GND	NA	Power and signal reference ground
20	5V	PWR	Output	5V @ 3A Max
21	5V	PWR	Output	5V @ 3A Max
22	5V	PWR	Output	5V @ 3A Max
23	GND	GND	NA	Power and signal reference ground
24	NC	NA	NA	Not connected to this pin
25	GND	GND	NA	Power and signal reference ground
26	NC	NA	NA	Not connected to this pin
27	NC	NA	NA	Not connected to this pin
28	NC	NA	NA	Not connected to this pin
29	SATA0_LED	IO	Output	SATA0 status for LED
30	SATA2_LED	IO	Output	SATA2 status for LED
31	GMAC0_MCLKINOUT	IO	I/O	CLOCK output 125MHz for GMAC0
32	GND	GND	NA	Power and signal reference ground
33	ETH0_REFCLKO_25M	IO	Output	CLOCK output 25MHz for GMAC0
34	GMAC0_MDIO	IO	I/O	GMAC management interface data
35	GND	GND	NA	Power and signal reference ground
36	GMAC0_MDC	IO	Output	GMAC management interface clock
37	GMAC0_RXDV_CRS	IO	Input	RGMII signal
38	GND	GND	NA	Power and signal reference ground
39	NC	NA	NA	Not connected to this pin
40	NC	NA	NA	Not connected to this pin
41	GND	GND	NA	Power and signal reference ground
42	NC	NA	NA	Not connected to this pin
43	NC	NA	NA	Not connected to this pin
44	GND	GND	NA	Power and signal reference ground
45	USB2_USB3_DM	LVDS	I/O	USB2.0 data signal Negative
46	USB2_USB3_DP	LVDS	I/O	USB2.0 data signal Positive
47	GND	GND	NA	Power and signal reference ground
48	GMAC0_RSTN_GPIO2_D3	IO	Output	RGMII signal
49	GMAC0_INT/PMEB_GPIO2_D2	IO	Input	RGMII signal
50	GND	GND	NA	Power and signal reference ground
51	GMAC0_RXCLK	IO	Output	RGMII signal
52	GND	GND	NA	Power and signal reference ground
53	GMAC0_TXD3	IO	Output	RGMII signal
54	GMAC0_TXD2	IO	Output	RGMII signal
55	GND	GND	NA	Power and signal reference ground
56	GMAC0_TXD1	IO	Output	RGMII signal
57	GMAC0_TXD0	IO	Output	RGMII signal
58	GND	GND	NA	Power and signal reference ground
59	GMAC0_TXCLK	IO	Output	RGMII signal
60	GND	GND	NA	Power and signal reference ground
61	SATA2_TXN	LVDS	Output	SATA data signal output Negative
62	SATA2_TXP	LVDS	Output	SATA data signal output Positive
63	GND	GND	NA	Power and signal reference ground
64	SATA2_RXN	LVDS	Input	SATA data signal Input Negative
65	SATA2_RXP	LVDS	Input	SATA data signal Input Positive
66	GND	GND	NA	Power and signal reference ground
67	PCIE20_REFCLKN	LVDS	Output	PCIE2.0 reference clock Negative
68	PCIE20_REFCLKP	LVDS	Output	PCIE2.0 reference clock Positive

SATA power connector

On the SATA power connector, pins 13 to 15 carry 12 V and pins 10 to 12 are ground.