Re: [Gumstix-users] using a MAXIM ADC over the I2C bus (MAX1238)

[Dave H. <dhy...@gm...>]

Hi Yuvraj,

Sorry about the last post - finger troubles.

> Is there any sample code for interfacing I2C devices
> with the gumstix ? Specifically is there any example
> code to read data using the I2C bus in C?

I've written a bunch of code for doing this. You can find it in the
robostix tree.
Grab the robostix code by doing these commands:

cd gumstix-buildroot
cd ..
svn co http://svn.gumstix.com/gumstix-buildroot/branches/projects/robostix
robostix

There is a general purpose program in robostix/gumstix/i2c
> I am
> looking for a fast data sampling and transfer. The MAX1238
> data sheet says that it supports 94.4Ksamples/s (it's a 12
> channel ADC) and I would like to be able to read it at
> least 1Ksamples/s per channel. Is this possible using the I2C bus?

Well, 1K samples/sec x 12 channels = 12,000 samples /sec.

The I2C bus runs at 100 kHz.

That's 8 bits/sample. Even if you increased the i2c speed to 400 kHz,
that would only be 32 bits/sample, so no I don't think it's possible.

> The data sheet mentions two modes of I2C ...which ones does the
> connex support ?

Perhaps you could be a bit more specific?

I see the Maxim part supports 1.7 Mbps, which the gumstix definitely
doesn't support.

-- 
Dave Hylands
Vancouver, BC, Canada
http://www.DaveHylands.com/