Ampro Corporation P5X manual Universal Serial Bus USB Ports, J24 Pin Signal Name Function

Universal Serial Bus (USB) Ports

The Universal Serial Bus connects USB devices with a USB host, in this case, the Little Board/P5x. The USB physical interconnect is a tiered star topology, or tree, consisting of hubs and USB devices. Each USB segment is a point-to-point connection between hubs or between hubs and USB devices. The entire tree can support up to 127 USB devices. The USB interface standard is intended for keyboards, mice, modems, digitizer pads, and other low- to medium-speed peripherals.

Each USB interface is implemented as a two-wire differential pair for data, a power wire, a ground wire, and a shield wire. The USB port signals appear on J24, the Utility2 connector, as shown in Table 2– 18.

Table 2– 18. USB Port Pinout on Utility2 Connector

J24 Pin	Signal Name	Function
15	USBPWR1	USB1 +5 Volt Power
17	USBP-1	USB1 Data-
19	USBP+1	USB1 Data+
21	USBGND1	Ground
23	SHIELD1	Cable Shield for USB1
16	USBPWR2	USB2 +5 Volt Power
18	USBP-2	USB2 Data-
20	USBP+2	USB2 Data+
22	USBGND2	Ground
24	SHIELD2	Cable Shield for USB2

The bus can run at 12 Mbits/second or 1.5 Mbits/second, depending on a pull-up on the peripheral device. A 1.5 KOhm pull-up on the +data line sets the speed to 12 Mbits/second. A 1.5 KOhm pull- up on the -data line sets the speed to 1.5 Mbits/second.

The power to the peripheral device is current limited with a self-resetting fuse.

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