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====USB battery charger====
====USB battery charger====
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The [http://focus.ti.com/docs/prod/folders/print/bq24150a.html bq24150a] charger from TI is a flexible charger. It, along with the PHY chip - support charging without the intervention of the SoC when the system is charging from a completely dead battery. The PHY chip detects a charger (shorted D+ and D- pins) and the charger uses this information to charge more rapidly.
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The [http://focus.ti.com/docs/prod/folders/print/bq24150.html bq24150] charger from TI is a flexible charger. It, along with the PHY chip - support charging without the intervention of the SoC when the system is charging from a completely dead battery. The PHY chip detects a charger (shorted D+ and D- pins) and the charger uses this information to charge more rapidly.
It also features reverse boost mode - which enables power to be supplied to a USB device connected to the N900. (up to a limit of 200mA)  
It also features reverse boost mode - which enables power to be supplied to a USB device connected to the N900. (up to a limit of 200mA)  
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There is no published datasheet for this chip. It may be available under another name.
There is no published datasheet for this chip. It may be available under another name.
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A reasonably similar chip (compare chips: [http://www.ebv.com/fileadmin/products/Products/ST-Ericsson/Flyer_USB_Transceivers_1.pdf]) is the 1704 which has a datasheet [http://www.stericsson.com/technical_documents/CD00222700.pdf]  
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A reasonably similar chip (compare chips: [http://www.ebv.com/fileadmin/products/Products/ST-Ericsson/Flyer_USB_Transceivers_1.pdf]) is the 1704 which has a datasheet [http://www.stericsson.com/technical_documents/CD00222700.pdf]
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Another equivalent chip seems to be the https://www.startpage.com/do/search?query=FUSB2500 - see http://talk.maemo.org/showthread.php?p=643577#post643577
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For more information see [[N900 Hardware USB PHY]]
For more information see [[N900 Hardware USB PHY]]
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* The SoC has the USB protocol controller - this is the 'high level' controller - it implements most of the USB protocol. This is a [http://www.mentor.com/products/ip/usb/usb20otg/ Mentorgrafix MUSBMHDRC-core] IntelectualProperty function block licenced for the OMAP.
* The SoC has the USB protocol controller - this is the 'high level' controller - it implements most of the USB protocol. This is a [http://www.mentor.com/products/ip/usb/usb20otg/ Mentorgrafix MUSBMHDRC-core] IntelectualProperty function block licenced for the OMAP.
* The PHY (physical layer) chip connects to the world through the USB socket. This is not the normal companion chip - but the NXP part, and is connected to the SoC via a standard ULPI interface. It does the very lowest level USB hardware protocol. Also it detects chargers (by sensing D+/D- short). It also has a connection to VBUS, via a 1k resistor, to do certain probing.
* The PHY (physical layer) chip connects to the world through the USB socket. This is not the normal companion chip - but the NXP part, and is connected to the SoC via a standard ULPI interface. It does the very lowest level USB hardware protocol. Also it detects chargers (by sensing D+/D- short). It also has a connection to VBUS, via a 1k resistor, to do certain probing.
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* The [[N900 Hardware Battery Charger|bq24150a Battery charger]]. This is connected to the battery, and the PHY chip, as well as to the SoC though I2C. It handles (with the PHY chip) charging from dead. It also implements boost mode, to enable powering things through the USB socket. Of course it detects when external VBUS is applied.
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* The [[N900 Hardware Battery Charger|bq24150 Battery charger]]. This is connected to the battery, and the PHY chip, as well as to the SoC though I2C. It handles (with the PHY chip) charging from dead. It also implements boost mode, to enable powering things through the USB socket. Of course it detects when external VBUS is applied.
* Gaia. The [[N900_Hardware_Power_management/I2C|TWL4030]] is used to sense the value of the ID pin. It also has a connection to VBUS, to power up the device on charger insertion and inform a running system about changes in VBUS state. Though TWL4030 has a function similar to PHY chip as well, the original design using this function had to change as early chip revisions had problems with charger detection (so the rumour). Driver sourecode is full of cruft from that original design.
* Gaia. The [[N900_Hardware_Power_management/I2C|TWL4030]] is used to sense the value of the ID pin. It also has a connection to VBUS, to power up the device on charger insertion and inform a running system about changes in VBUS state. Though TWL4030 has a function similar to PHY chip as well, the original design using this function had to change as early chip revisions had problems with charger detection (so the rumour). Driver sourecode is full of cruft from that original design.
===The Software===
===The Software===
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* [[N900 Software BME|BME]] - the battery managment entity. This has its hands in everything, especially the bq24150a, and is split into
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* [[N900 Software BME|BME]] - the battery managment entity. This has its hands in everything, especially the bq24150, and is split into
** charger detection (via PHY) in kernel MUSB_HDRC driver, exposing /sys/devices/platform/musb_hdrc/charger
** charger detection (via PHY) in kernel MUSB_HDRC driver, exposing /sys/devices/platform/musb_hdrc/charger
** BME - userspace driver for the charger chip, as well as monitoring battery voltage through Gaia.
** BME - userspace driver for the charger chip, as well as monitoring battery voltage through Gaia.
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==Host mode details.==
==Host mode details.==
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Host mode works, see [http://talk.maemo.org/showthread.php?p=901888#post901888 this thread] Mohammad started on talk.maemo.org, when releasing first beta of a package comprising of a hostmode patched kernel build by Paul Fertser with support of h-e-n team, and a lean GUI built by Mohammad. The basic functionality seems to work fine.
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Host mode works, see [http://talk.maemo.org/showthread.php?p=901888#post901888 this thread] Mohammad started on talk.maemo.org, when releasing first beta of a package comprising of a hostmode patched kernel build by the Paul Fertser with support by h-e-n team, and a lean GUI built by Mohammad. The basic functionality seems to work fine.
   
   
A [[N900_Hardware_USB_Host|user friendly implementation]] that makes it easy to use host mode needs a lot more than this, e.g. proper automounting, clean unmounting and sync, drivers for all kinds of peripherals etc.
A [[N900_Hardware_USB_Host|user friendly implementation]] that makes it easy to use host mode needs a lot more than this, e.g. proper automounting, clean unmounting and sync, drivers for all kinds of peripherals etc.
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Initially it was claimed that ID is not connected externally, and that this made USB host mode impossible.
Initially it was claimed that ID is not connected externally, and that this made USB host mode impossible.
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While this is mostly correct, it needs some exemplification:
 
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* the ID pin is not connected to PHY, but it is connected to GAIA
 
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* MUSB-core has a hw statemachine that reacts on a telegram from PHY, telling MUSB-core about ID pin grounded and to enter OTG_A hostmode now.
 
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* Other PHY chips (e.g. in N810) have a command to make them send this telegram, so you can switch MUSB-core to hostmode under software control (go figure!). 1707 is missing this function.
 
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* There is apparently no way to tell MUSB-core directly to switch to hostmode in a natural way.
 
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* However there is a bit in MUSB-core registers called FORCE_HOST, which is switching MUSB-core into a semi-lobotomized test mode and allowed us to implement h-e-n.
 
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===the following text needs update, it doesn't represent current state of investigation results anymore (corrections in ''(italic)'')===
 
However, similar device datasheets indicate that the ID pin is used on hardware that supports it to switch between host and device mode.
However, similar device datasheets indicate that the ID pin is used on hardware that supports it to switch between host and device mode.
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But, importantly, the ID pin does nothing directly to the state of the PHY. It simply informs the CPU ''(the MUSB-core)'' of the state of the ID pin, and leaves the driver to properly configure the chip (nota bene, only for OTG, and only for determining the inital state).
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But, importantly, the ID pin does nothing directly to the state of the PHY. It simply informs the CPU of the state of the ID pin, and leaves the driver to properly configure the chip (nota bene, only for OTG, and only for determining the inital state).
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So, if the kernel can be altered to ignore this pin - which should be trivial if there is host mode support for the chip in the kernel ''(the hw statemachine in MUSB-core won't play nice with whatever kernel does to enable hostmode in a "normal" way)''- then host mode works.(the related sourcecode is to be found here:[http://mxr.maemo.org/fremantle/source/kernel/drivers/usb/musb/musb_core.c#2010], a 'echo host >mode' should work if the kernel driver wasn't crippled in some strange way)''(h-e-n kernel hostmode now is working like this, but still needs another 'echo Fx >/proc/drivers/musb-hdrc' where 'x' is depending on speed. The kernel is "crippled" in a way it can not send a command to PHY to switch to hostmode, as the 1707 '''seems''' doesn't support this - further investigation needed, maybe it has this command but it isn't documented. Or we can spoof this command rsp the resulting telegram)''
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So, if the kernel can be altered to ignore this pin - which should be trivial if there is host mode support for the chip in the kernel - then host mode works.(the related sourcecode is to be found here:[http://mxr.maemo.org/fremantle/source/kernel/drivers/usb/musb/musb_core.c#2010], a 'echo host >mode' should work if the kernel driver wasn't crippled in some strange way)
The current understanding by several people who are working on USB host mode is:
The current understanding by several people who are working on USB host mode is:
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The USB port can supply power - at least 200mA (as demonstrated here:[http://talk.maemo.org/showthread.php?p=588950#post588950]). This is plenty for many devices - mice and keyboards.
The USB port can supply power - at least 200mA (as demonstrated here:[http://talk.maemo.org/showthread.php?p=588950#post588950]). This is plenty for many devices - mice and keyboards.
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It seems likely that a relatively simple kernel change should enable USB hostmode - http://focus.ti.com/lit/ug/spruf98d/spruf98d.pdf - search for FORCE_HOST - there may well be other cleaner solutions. ''(h-e-n is exploiting this. About the "relatively simple" part that's up to your discretion)
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It seems likely that a relatively simple kernel change should enable USB hostmode - http://focus.ti.com/lit/ug/spruf98d/spruf98d.pdf - search for FORCE_HOST - there may well be other cleaner solutions.
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''
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A possibly related errata is detailed at 3.1.3 in [http://focus.ti.com/lit/er/sprz278d/sprz278d.pdf this document] - this, and other erratas may or may not cause issues with implementing host mode.
A possibly related errata is detailed at 3.1.3 in [http://focus.ti.com/lit/er/sprz278d/sprz278d.pdf this document] - this, and other erratas may or may not cause issues with implementing host mode.
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{{main|N900 Hardware USB Socket}}
{{main|N900 Hardware USB Socket}}
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===Compatible devices===
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[[Category:N900_Hardware]]
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{| class="wikitable sortable"
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|+ Compatible USB devices
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|-
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! USB device name
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! Status
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! class="unsortable" | Additional information
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! Additional driver needed
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! class="unsortable" | Discussion link
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|-
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| Edimax EU-4207 || Working || no problems found || <code>no</code> || http://talk.maemo.org/showthread.php?t=66667
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|-
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| ZTE-AC2766 || Working || no problems || <code>no, uses usbserial.ko</code> || http://talk.maemo.org/showpost.php?p=1198785&postcount=13
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|-
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|}
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[[Category:N900 Hardware]]
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