I2C_SMBUS_WORD Definition

I2C_SMBUS_WORD Definition

[Gary Chambers]

All...

Please forgive my ignorance and naivete, but will someone please tell me 
why i2c_smbus_read_word doesn't exist?  Thank you very much!

-- 
Gary Chambers

// -------------------------------------
// Advanced SatComm Systems & Operations
// MIT Lincoln Laboratory / 781-981-0957
// Lexington, Massachusetts
// Nothing fancy and nothing Microsoft
// -------------------------------------

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Re: I2C_SMBUS_WORD Definition

[Jean Delvare]

Hi Gary,

On Fri, 18 Jan 2008 15:30:56 -0500 (EST), Gary Chambers wrote:
> Please forgive my ignorance and naivete, but will someone please tell me 
> why i2c_smbus_read_word doesn't exist?  Thank you very much!

i2c_smbus_read_word_data() does exist, isn't it what you are looking
for? It corresponds to a "read word" transaction in SMBus terminology.

-- 
Jean Delvare

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Re: I2C_SMBUS_WORD Definition

[Gary Chambers]

Jean...

Thanks for the reply!

> i2c_smbus_read_word_data() does exist, isn't it what you are looking
> for? It corresponds to a "read word" transaction in SMBus terminology.

i2c_smbus_read_word_data() implies (to me, anyway) a required 
data/command in the transaction.  Some of the devices with which we deal 
apparently cannot tolerate this extra 8 bits on the bus when attempting 
to read a word from them.  The bus analyzer also indicates those extra 
bits are present.  I'm doing my work through the dev interface, and our 
functionality matrix seems to indicate that I cannot use pure I2C.  Any 
thoughts or insight?  Thanks very much!

-- 
Gary Chambers

// -------------------------------------
// Advanced SatComm Systems & Operations
// MIT Lincoln Laboratory / 781-981-0957
// Lexington, Massachusetts
// Nothing fancy and nothing Microsoft
// -------------------------------------

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Re: I2C_SMBUS_WORD Definition

[Jean Delvare]

Hi Gary,

On Sat, 19 Jan 2008 15:55:42 -0500 (EST), Gary Chambers wrote:
> > i2c_smbus_read_word_data() does exist, isn't it what you are looking
> > for? It corresponds to a "read word" transaction in SMBus terminology.
> 
> i2c_smbus_read_word_data() implies (to me, anyway) a required 
> data/command in the transaction.

That's correct, the "read word" SMBus transaction first writes a
"command" byte to the device (typically a register address in the
device) before reading two bytes from it.

>                                   Some of the devices with which we deal 
> apparently cannot tolerate this extra 8 bits on the bus when attempting 
> to read a word from them.  The bus analyzer also indicates those extra 
> bits are present.  I'm doing my work through the dev interface, and our 
> functionality matrix seems to indicate that I cannot use pure I2C.  Any 
> thoughts or insight?  Thanks very much!

Well, reading two bytes from a device directly doesn't correspond to any
SMBus transaction, so if your bus controller doesn't support I2C
messaging, I fear that you're pretty much stuck. What adapter is this?
And what chip are you trying to talk to?

-- 
Jean Delvare

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Re: I2C_SMBUS_WORD Definition

[Gary Chambers]

Jean...

> Well, reading two bytes from a device directly doesn't correspond to 
> any SMBus transaction, so if your bus controller doesn't support I2C 
> messaging, I fear that you're pretty much stuck.

How authoritative is the functionality matrix?  My call to it returns 
0xcfffc006 -- no pure I2C, but it appears that I can perform I2C block 
writes and reads.

> What adapter is this?  And what chip are you trying to talk to?

It's a [seemingly] simple TI DAC5571 (single-channel, 8-bit DAC) on an 
evaluation module.

Thanks for your (and the list's) patience while I gain some footing with 
this.

-- 
Gary Chambers

// -------------------------------------
// Advanced SatComm Systems & Operations
// MIT Lincoln Laboratory / 781-981-0957
// Lexington, Massachusetts
// Nothing fancy and nothing Microsoft
// -------------------------------------

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Re: I2C_SMBUS_WORD Definition

[Jean Delvare]

Hi Gary,

On Mon, 21 Jan 2008 14:17:00 -0500 (EST), Gary Chambers wrote:
> > Well, reading two bytes from a device directly doesn't correspond to 
> > any SMBus transaction, so if your bus controller doesn't support I2C 
> > messaging, I fear that you're pretty much stuck.
> 
> How authoritative is the functionality matrix?  My call to it returns 
> 0xcfffc006 -- no pure I2C, but it appears that I can perform I2C block 
> writes and reads.

The functionality matrix can be trusted in general, but if you'd tell
me what i2c adapter driver this is, I could double-check. Also note
that "i2cdetect -F" can list the functionality in a much more
human-friendly format.

> > What adapter is this?  And what chip are you trying to talk to?
> 
> It's a [seemingly] simple TI DAC5571 (single-channel, 8-bit DAC) on an 
> evaluation module.

Are you sure that the TI DAC5571 DAC value can be read at all? I've
downloaded the datasheet and all it mentions is writing to the DAC5571,
not reading from it.

> Thanks for your (and the list's) patience while I gain some footing with 
> this.

You're welcome.

-- 
Jean Delvare

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DAC5571

[Gary Chambers]

Jean...

> Are you sure that the TI DAC5571 DAC value can be read at all? I've 
> downloaded the datasheet and all it mentions is writing to the 
> DAC5571, not reading from it.

It appears that you're correct!  I was lead down the primrose path by 
someone who assumed it was a device which provided read access to the 
analog output setting.  My cover is blown -- it's now official that 
everyone knows definitively that I know little to nothing about what I'm 
doing.  :)

I don't know how beneficial it will be, but I have nearly completed a 
driver for the DAC5571.  We're currently using Linux 2.4 in our embedded 
project, but we may soon be upgrading to a 2.6 kernel.

> The functionality matrix can be trusted in general, but if you'd tell 
> me what i2c adapter driver this is, I could double-check. Also note

We're using the tqm8260Algorithm-bit adapter.  Are you familiar with it?

-- 
Gary Chambers

// -------------------------------------
// Advanced SatComm Systems & Operations
// MIT Lincoln Laboratory / 781-981-0957
// Lexington, Massachusetts
// Nothing fancy and nothing Microsoft
// -------------------------------------

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Re: DAC5571

[Jean Delvare]

Hi Gary,

On Wed, 23 Jan 2008 15:48:09 -0500 (EST), Gary Chambers wrote:
> I don't know how beneficial it will be, but I have nearly completed a 
> driver for the DAC5571.  We're currently using Linux 2.4 in our embedded 
> project, but we may soon be upgrading to a 2.6 kernel.

A Linux 2.4 driver obviously won't make it upstream, but a Linux 2.6
driver could. You can always post your code on the i2c list, where it
will be archived for other users to look at. If there are more users
interested, the driver can be reviewed and merged upstream.

> (...)
> We're using the tqm8260Algorithm-bit adapter.  Are you familiar with it?

Never heard of that one, it's not upstream as far as I can see.

-- 
Jean Delvare

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