Thanks Meter 10
Join Date: Mar 2009
Location: Baltimore, MD, USA
Originally Posted by fafler
If it's not a resistor, then what do you suggest?
seems to be the best piece of information on resistors, but none of them seems to be what we want.
---------- Post added at 10:19 PM ---------- Previous post was at 09:36 PM ----------
I've been digging a bit more in the datasheet, and the tables in chapter 6.5 and 5.3 gives us all we need. It seems to be nothing more than a 119 to 132 kΩ resistor and the phone will charge while still providing OTG functionality. I think i have a spare micro USB connector in a drawer somewhere, so i'll try this out ASAP :)
---------- Post added at 10:33 PM ---------- Previous post was at 10:19 PM ----------
The PDF says:
3) Nominal values for these resistors are RID_A = 124k, RID_B = 68k and RID_C = 36.5k.
The Fun with resistors thread says:
RID_RESERVED_1, /* 0 1 1 1 0 28.7K Reserved Accessory #1 */
RID_RESERVED_2, /* 0 1 1 1 1 34K Reserved Accessory #2 */
RID_RESERVED_3, /* 1 0 0 0 0 40.2K Reserved Accessory #3 */
RID_RESERVED_4, /* 1 0 0 0 1 49.9K Reserved Accessory #4 */
RID_RESERVED_5, /* 1 0 0 1 0 64.9K Reserved Accessory #5 */
RID_AUD_DEV_TY_2, /* 1 0 0 1 1 80.07K Audio Device Type 2 */
RID_PHONE_PWD_DEV, /* 1 0 1 0 0 102K Phone Powered Device */
RID_TTY_CONVERTER, /* 1 0 1 0 1 121K TTY Converter */
RID_UART_CABLE, /* 1 0 1 1 0 150K UART Cable */
It's pretty close, 121 vs 124 k, 64.9 vs 68 and 34 k vs 36.5 k, and actually quite weird the ACA modes arent listened in the source. Is this wrong? Is the 124 k resistor going to trigger TTY converter mode, whatever that is, instead? I guess i can find the answers in the kernel logs when i try it out.
if you look at the pdf table 5-3 you will see the acceptable range:
RID_A = 119k ~ 132k (nominal is 124k)
RID_B = 65k ~ 72k (nominal is 68k) so 64.9k (from the other thread) is a bit below the range and i think it is saver to stick with the one suggested in the pdf
RID_C = 35k ~ 39k (nominal is 36.5k)
so we can use these resistors plus RID_FLOAT and RID_GND to switch between the modes of operation defined in the pdf table 6-2. So if we want the ASA to operate on more than one mode then I guess we will need some kind of a circuit to detect the attached devices in order to switch to the right RID. However, if we want a simple design for only 1 mode (or just as a prove of concept) then we can pick only 1 of them and have it hard wired to the OTG ID pin, (guessing again).
my only concern is what is going to happen if i hardwired only 1 mode but then had a different device setup, like no charger or more than 1 attached device (like if i used a hub and connected two flash drives)
i was able to connect a normal (un-powered) usb hub to my Galaxy Note using a normal OTG cable (ID=GND) and then i connected a wireless mouse dongle, wired keyboard and a 2GB flash drive in to the hub and my phone was able to provide enough power to all and i was using the mouse and keyboard while browsing files on the flash drive but everything failed as i plugged in a second flash drive (just to stress test it) since the phone couldn't provide enough current.
Maybe we can modify a powered hub to act as an ASA
by the way "fafler" did you get any results?