[ Cc:s trimmed ] [EMAIL PROTECTED] wrote: > Now if we detect there's not 0volt but instead there's 5volt on the ID-pin > while we're applying 0volt to internal R, we got a new info about what's > plugged to our USB-receptacle, and we might ->>route this 5volt to our > PMU<<-.
So the proposal is to make a Y-cable that connects ID to VBUS. The cable would not be permanently attached to any devices (i.e., a fixed charger cable). The connectors would be A-A/B(1)-B(2), where A goes to a host providing power or our charger, A/B(1) goes to the Neo, and B(2) goes to a device that may in turn be OTG-capable. Correct so far ? Micro-USB_1_01.pdf, page 10, below table 4-2 says: | The ID pin on a Micro-A plug shall be connected to the GND pin. So the ID = VBUS arrangement would violate this. Of course, a Y-cable would violate Micro-USB 1.01 as well :-) | No other types of cables are allowed by either the USB specification, | or by the OTG supplement. (Page 8.) The Micro-USB is silent about the use of ID in receptacles, particularly on the A-side. If we make a worst-case assumption that ID is just connected to GND, we could possibly damage the device. In order to avoid this sort of problem, ID on the A-side would have to be unconnected, and the connection between ID and VBUS would have to be made further down the cable, i.e., inside the A/B(1) connector. | The ID pin on a Micro-B plug is not connected or is connected to ground | by a resistance of greater than Rb_PLUG_ID (100kOhm MIN). So actually having 5V on ID on A/B(1) or even B(2) shouldn't damage a compliant device. (I.e., if the cable is used with some device that's not a Neo.) For compatibility with OTG, B(2).ID would have to be connected to GND. So the overall connections would be roughly as follows: A A/B(1) B(2) VBUS -----+----- VBUS ----------- VBUS ID -- \---- ID -- /----- ID GND ----------- GND -----+----- GND Is this what you had in mind ? Since the Neo side receptacle would have to be AB, what would the plug be - A or B ? BTW, regarding doing measurements through GPIO+R instead of rail+R, I think this is in general good practice giving one flexibility for usually little cost. - Werner _______________________________________________ hardware mailing list [email protected] http://lists.openmoko.org/mailman/listinfo/hardware
