N900 will not allow USB OTG! - Page 64 - maemo.org

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egoshin	2010-03-19 , 23:20
Posts: 992 \| Thanked: 995 times \| Joined on Dec 2009 @ California	#631

Originally Posted by joerg_rw

As far as the recently leaked schematics are correct, VBUS is hooked up to GAIA TWL4030 PMU chargepump to deliver a correct 5V supply - rather than to the PHY chip.

Alas I've not found any matching node in sysfs to enable the GAIA vbus chargepump. Access to the related register via I2C should be possible nebertheless

jOERG

Can you point me to schematics?

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	qole	2010-03-19 , 23:37
	Moderator \| Posts: 7,109 \| Thanked: 8,820 times \| Joined on Oct 2007 @ Vancouver, BC, Canada	#632

Originally Posted by geohsia

I tried reading as much of this as I could but I wasn't sure what would happen in my scenario. I own the following HDD:

http://www.hypershop.com/HyperDrive-COLORSPACE-s/23.htm

This drive has an internal battery to drive operation because of the screen and etc. There is a connector to take power from a battery or wall jack if you want extra juice to recharge while in use.

My question is I know the N900 doesn't supply power in its USB connection, so since this drive doesn't need power from the USB, can I get it to work with the N900?

I am a photographer that works on the road. With this I could send files from anywhere in the world that has cell coverage without the need for bringing a laptop. This would be HUGE. Any suggestions? Thanks.

Use a camera that uses SD cards. Buy a micro-SD card with an SD adapter. Put the microSD with adapter into the camera, take lots of pictures. Take the microSD out of the camera, put it into the N900. Send the pictures over the Internet.

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	joerg_rw	2010-03-20 , 00:48
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Originally Posted by egoshin

Can you point me to schematics?

http://wiki.maemo.org/N900_Hardware_Schematic

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sarahn	2010-03-20 , 01:04
Posts: 243 \| Thanked: 172 times \| Joined on Sep 2007 @ silicon valley	#634

joerg_rw, are we certain thats the rx51 and not the rx71? It seems rather odd to have power available and connect id to twl4030 and not support usb host.

The PHY can't supply power but it can enable an external charge pump. I hadn't seriously considered and put the probability of that doing anything rather low, that but it's easy to try.

	joerg_rw	2010-03-20 , 15:36
	Posts: 2,222 \| Thanked: 12,651 times \| Joined on Mar 2010 @ SOL 3	#635

Originally Posted by sarahn

joerg_rw, are we certain thats the rx51 and not the rx71? It seems rather odd to have power available and connect id to twl4030 and not support usb host.

The PHY can't supply power but it can enable an external charge pump. I hadn't seriously considered and put the probability of that doing anything rather low, that but it's easy to try.

Well, all the pages read "Version: 2.0 | 07.10.2009 | N900/RX-51 | Board version: 2JH_21a "

It's quite possible the board rev of MP devices is a little different, though 2009-10-07 (if that's the correct way to read this) on schematics makes me think it isn't completely different from what shipped 6 weeks later.

Anyway for switching the port to hostmode it's not a big thing if ID is connected to PHY or anything else, and also it doesn't matter you have to enable VBUS via register config. You need to disable bat charging via USB same time you're enabling VBUS charge pump (this is no perpetuum mobile ;-). All the issues arising from OTG protocol complexity are neglegtable for a simple manually enabled host mode.

jOERG

	joerg_rw	2010-03-20 , 15:53
	Posts: 2,222 \| Thanked: 12,651 times \| Joined on Mar 2010 @ SOL 3	#636

From TWL4030__TPS65950 OMAP™ Power Management and System Companion Device ES 1.0 TRM (Rev. D)__swcu050d (TI publically available docs):

(page 869)
**Table 15-40. OTG_CTRL**
Address Offset 0x0A
Description Controls UTMI+ OTG functions of the PHY
Type RW

Bit: 5
Field Name: DRVVBUS
Description:
. Signals the internal charge pump to drive 5 V on VBUS
. 0b: Do not drive VBUS.
. 1b: Drive 5 V on VBUS.
Type: RW
Reset 0

sarahn	2010-03-20 , 18:23
Posts: 243 \| Thanked: 172 times \| Joined on Sep 2007 @ silicon valley	#637

Originally Posted by joerg_rw

From TWL4030__TPS65950 OMAP™ Power Management and System Companion Device ES 1.0 TRM (Rev. D)__swcu050d (TI publically available docs)

Yes, the schematic has the isp170x, see ref D4380. The pinouts match for that part and the schematic's USB diagram matches my understanding where the ID pin goes to the twl4030 but not the isp170x.

The schematic answers one of my questions - how is CHGR_DET_EN_N wired? The schematic shows it as being permanently grounded. "If CHGR_DET_EN_N is LOW, and when the ISP1704A is in power down-mode, on detecting VBUS > Vth(r)(VBUS), the ISP1704A will perform automatic USB battery charger detection." The datasheet also says "When used as a host or an OTG A-device transceiver, it is recommended that the CHGR_DET_EN_N pin is deasserted." So I don't know if USB host will work as long as the PHY doesn't get powered down, or if that signal being permanently enabled means it's pretty much impossible to negotiate a connection as host.

Last edited by sarahn; 2010-03-20 at 19:02.

sarahn	2010-03-20 , 18:33
Posts: 243 \| Thanked: 172 times \| Joined on Sep 2007 @ silicon valley	#638

Originally Posted by joerg_rw

Well, all the pages read "Version: 2.0 | 07.10.2009 | N900/RX-51 | Board version: 2JH_21a "

It's quite possible the board rev of MP devices is a little different, though 2009-10-07 (if that's the correct way to read this) on schematics makes me think it isn't completely different from what shipped 6 weeks later.

7.10.2009 could theoretically be July 10, 2009 depending on your perspective.

Originally Posted by joerg_rw

All the issues arising from OTG protocol complexity are neglegtable for a simple manually enabled host mode.
jOERG

Have you done it already then?

	pelago	2010-03-20 , 22:45
	Posts: 2,121 \| Thanked: 1,540 times \| Joined on Mar 2008 @ Oxford, UK	#639

Originally Posted by sarahn

7.10.2009 could theoretically be July 10, 2009 depending on your perspective.

Looking at the properties of that PDF, I see:

Created: Mon 31 Aug 2009 14:27:59 BST
Modified: Wed 07 Oct 2009 10:59:49 BST

sarahn	2010-03-20 , 23:22
Posts: 243 \| Thanked: 172 times \| Joined on Sep 2007 @ silicon valley	#640

Originally Posted by pelago

Looking at the properties of that PDF, I see:

Created: Mon 31 Aug 2009 14:27:59 BST
Modified: Wed 07 Oct 2009 10:59:49 BST

Having not been able to see the schematic before posting that, I thought perhaps it showed the twl4030 as the phy. That's not the case.

So the twl4030 (cribbing from the tps65950 datasheet) can drive vbus using an integrated charge pump. In order to drive vbus, cp.in needs to be connected to vbat. It is. r6 (cp.gnd) is grounded which is also good. However, I don't see any indication of the CP flying capacitor being present. According to wikipedia, the source of all knowledge, a charge pump uses a capacitor to operate. AFAIK that would not be integrated with the twl4030, so the charge pump can't operate. I also don't see vbus going to any other power supply.

So the question is, why not have the charge pump? The 4 things I can think of is a) it added too much noise b) it doesn't actually work c) it can't supply enough power to meet spec d) it's stupid and tries to charge itself off its own charge pump.

Or perhaps there is no integrated charge pump on the chip they used. As I understand charge pumps are expensive and they may have decided the demand didn't justify the additional cost.

Also, even though the ID pin is connected to the twl4030, I suspect that normally this interrupt needs to be signaled through the ulpi interface (I think that's what normally happens) which the twl4030 can't do.

Last edited by sarahn; 2010-03-21 at 00:02.