Re: N900 will not allow USB OTG!
 

Can you point me to schematics?

Re: N900 will not allow USB OTG!
 

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.

Re: N900 will not allow USB OTG!
 

Re: N900 will not allow USB OTG!
 

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.

Re: N900 will not allow USB OTG!
 

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

Re: N900 will not allow USB OTG!
 

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

Re: N900 will not allow USB OTG!
 

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.

Re: N900 will not allow USB OTG!
 

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

Have you done it already then?

Re: N900 will not allow USB OTG!
 

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

Re: N900 will not allow USB OTG!
 

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.