how to slow down bus frequency.

padmanabha at tesbv.com padmanabha at tesbv.com
Thu Sep 18 05:17:36 CDT 2008


Hi GabrieleF,

Currently i2c-adapter driver is hard coded (variable bus_freq = 20) to  
work at 20Khz ( check in probe function) on dvevm.
Try to reduce it if you need to slow down bus frequency :)

STANDARD SPEED -- 100K hz
FASTEST SPEED  -- 400K hz for I/O expander.


Padmanabha S


padmanabha.s
Quoting davinci-linux-open-source-request at linux.davincidsp.com:

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> Today's Topics:
>
>    1. RE: Where can I find mt9t001.c (Phil Quiney)
>    2. R: I2C bus probe utility (Gabriele Filosofi)
>    3. I: I2C bus probe utility (Gabriele Filosofi)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Thu, 18 Sep 2008 08:11:55 +0100
> From: "Phil Quiney" <PQuiney at trinityconvergence.com>
> Subject: RE: Where can I find mt9t001.c
> To: "Ying Huang" <huangying581 at gmail.com>,
> 	<davinci-linux-open-source at linux.davincidsp.com>
> Message-ID:
> 	<864811E44DB83D4DB83B667A4631E755FD4129 at nurburg.Trinity.local>
> Content-Type: text/plain;	charset="iso-8859-1"
>
> Hi,
>
> Could you not have searched for them rather than giving up as soon   
> as they were not where you thought they should be. It took seconds   
> to find them.....
>
> cd linux-2.6.10_mvl401
> find . -name mt9t001.[ch]
> ./drivers/media/video/davinci/mt9t001.c
> ./include/media/davinci/mt9t001.h
> ./include/config/video/mt9t001.h
>
> Regards
>
> Phil Q
>
>
> Phil Quiney, Senior Software Engineer
> Trinity Convergence
> Cambridge Business Park
> Cowley Road
> Cambridge CB4 0WZ, UK
> T: +44(0)1223-435536
> F: +44(0)1223-435560
> www.trinityconvergence.com
>
>
> -----Original Message-----
> From: davinci-linux-open-source-bounces at linux.davincidsp.com   
> [mailto:davinci-linux-open-source-bounces at linux.davincidsp.com] On   
> Behalf Of Ying Huang
> Sent: 18 September 2008 04:45
> To: davinci-linux-open-source at linux.davincidsp.com
> Subject: Where can I find mt9t001.c
>
> Hi,
>
>     I have checked the following folder:
>
> \home\icer\workdir\lsp\ti-davinci\drivers\media\video\
> \home\icer\workdir\lsp\ti-davinci\include\media\
>
> and I can not find either mt9t001.c nor mt9t001.h file.
>
> I did all of the setting as this literature:
> LSP 1.20 DaVinci Linux CCDC Driver
> User's Guide
> Literature Number: SPRUEP7
>
>
> <*> Video for Linux option
> --> <M> Davinci Video Capture
>
> Could anybody tell me how to find those files or mail me a copy as   
> attachment? Thank you !
>
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>
>
> ------------------------------
>
> Message: 2
> Date: Thu, 18 Sep 2008 09:35:05 +0200
> From: Gabriele Filosofi <GabrieleF at cosmed.it>
> Subject: R: I2C bus probe utility
> To: Vim Venture <cglrep at vimventure.com>
> Cc: "davinci-linux-open-source at linux.davincidsp.com"
> 	<davinci-linux-open-source at linux.davincidsp.com>
> Message-ID:
> 	<E88FCB96E0A8D34FA0BC3F7BBEF1609B1C74967205 at ServerMail.intranet.cosmed.it>
>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Vim,
>
> I've checked yet those folders. The I2C address of my physical   
> device should be 0x21 (videocam OV7670), so I would expect to find a  
>  device file
>
> /sys/bus/i2c/devices/1-0021
>
> But I don't see it.
> Instead I see the installed driver
>
> /sys/bus/i2c/drivers/ov7670
>
> I'm wandering if anybody knows how to speed down the I2C bus.
>
> Gabriele
>
> Da: Vim Venture [mailto:cglrep at vimventure.com]
> Inviato: mercoledì 17 settembre 2008 18.47
> A: Gabriele Filosofi
> Cc: davinci-linux-open-source at linux.davincidsp.com
> Oggetto: Re: I2C bus probe utility
>
> Hi Gabriele,
>
> I used the device and driver files in   /sys/bus/i2c/devices   and    
>   /sys/bus/i2c/drivers   to help debug my i2c problems.  You can see  
>  which devices are registered and what drivers are available.
> I did not have to change the bus speed, so I haven't looked into that.
>
> Hope that helps,
> -Vim
>
> On Sep 17, 2008, at 5:56 AM, Gabriele Filosofi wrote:
>
>
> Hi,
>
> I'm facing with some problems on the I2C bus.
> In the u-boot command list there is a specific command to probe all   
> valid addresses on the I2C bus (iprobe), but I'm not sure it is   
> working good.
>
>
>  1.  Is there any similar utility within the kernel?
>  2.  How can I reduce the bus speed?
>
> Regards,
>
> Gabriele
>
>
>
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> ------------------------------
>
> Message: 3
> Date: Thu, 18 Sep 2008 09:58:38 +0200
> From: Gabriele Filosofi <GabrieleF at cosmed.it>
> Subject: I: I2C bus probe utility
> To: Vim Venture <cglrep at vimventure.com>
> Cc: "davinci-linux-open-source at linux.davincidsp.com"
> 	<davinci-linux-open-source at linux.davincidsp.com>
> Message-ID:
> 	<E88FCB96E0A8D34FA0BC3F7BBEF1609B1C74967219 at ServerMail.intranet.cosmed.it>
>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Vim,
>
> I've solved eliminating a couple of 22 ohm resistors I placed in   
> series on the bus lines.
>
> Thanks
>
> Gabriele
>
> Da: Gabriele Filosofi
> Inviato: giovedì 18 settembre 2008 9.40
> A: 'Vim Venture'
> Cc: 'davinci-linux-open-source at linux.davincidsp.com'
> Oggetto: R: I2C bus probe utility
>
> Vim,
>
> I've checked yet those folders. The I2C address of my physical   
> device should be 0x21 (videocam OV7670), so I would expect to find a  
>  device file
>
> /sys/bus/i2c/devices/1-0021
>
> But I don't see it.
> Instead I see the installed driver
>
> /sys/bus/i2c/drivers/ov7670
>
> I'm wandering if anybody knows how to speed down the I2C bus.
>
> Gabriele
>
> Da: Vim Venture [mailto:cglrep at vimventure.com]
> Inviato: mercoledì 17 settembre 2008 18.47
> A: Gabriele Filosofi
> Cc: davinci-linux-open-source at linux.davincidsp.com
> Oggetto: Re: I2C bus probe utility
>
> Hi Gabriele,
>
> I used the device and driver files in   /sys/bus/i2c/devices   and    
>   /sys/bus/i2c/drivers   to help debug my i2c problems.  You can see  
>  which devices are registered and what drivers are available.
> I did not have to change the bus speed, so I haven't looked into that.
>
> Hope that helps,
> -Vim
>
> On Sep 17, 2008, at 5:56 AM, Gabriele Filosofi wrote:
>
> Hi,
>
> I'm facing with some problems on the I2C bus.
> In the u-boot command list there is a specific command to probe all   
> valid addresses on the I2C bus (iprobe), but I'm not sure it is   
> working good.
>
>
>  1.  Is there any similar utility within the kernel?
>  2.  How can I reduce the bus speed?
>
> Regards,
>
> Gabriele
>
>
>
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> Davinci-linux-open-source mailing list
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