USB
From Gumstix User Wiki
| USBH_PWR1 | Pull-up to 3.3 volts to enable USB port | |
| USBH_PEN1 | ||
| USBH_P1 | USB port | USB D+ |
| USBH_N1 | USB D- | |
| V_BATT | USB VBUS | |
| GND | USB DGND | |
The 24-pin flex ribbon connector has USB port 1 on it. The pinouts you need are:
- V_BATT (pin 24) - USB power
- USBH_N1 (pin 18) - USB D-
- USBH_P1 (pin 17) - USB D+
- GND (pin 8) - USB Ground
In addition, you need to pull USBH_PWR1 (pin 20) up to 3.3 volts to enable the port. You need to provide a stable 3.3 volt supply, which is fairly simple to do by adding a small SOT23 package voltage regulator (like the LM3480), with the power input coming from V_BATT (pin 24) and the output going to USBH_PWR1 (pin 20).
WARNING: This information could be yet inaccurate. TODO: D+/D- pull-down resistors (software?), termination resistors and capacitors for EMI suppresion, plus USBH_PEN1 and USBH_PWR1
Examples
U1: LM3480
C1,C2: 0.1uF
(read warning above)
Related
Universal Serial Bus Revision 2.0 specification
Open HCI—Open Host controller Specification for USB
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