Now, I tested the rewrite of the i2c kernel mode driver from http://www.gevawebsolutions.com/wiki/index.php?title=FB_General_Issues The sample code is worth to try. But with the PCF8591 I can set the A/D converter, measured with a voltmeter. The D/A conversion doesn't work. Testet with and without pull up resistor. Sometimes the value differs from 0x00. What could be the problem? I can't visual the lines, because no osciloscope.
--- In [email protected], Eberhard Fahle <[EMAIL PROTECTED]> wrote: > > On Mittwoch, 21. Februar 2007 gazoox22 wrote: > > Greetings. > > > > For now, I have tested your code. It runs, but what I get from the I2C > > bus is the byte 0x80, so I think the PCF8591 is sending something > > back. At the moment I dont' use any pull up resistors, but get the > > same results with 10k on SCK and/or SDA. My Vref is 3,3V. > > > > Please help. > > I'm not quite sure what your problem is, but 0x80 as the first data to be > returned from an PCF8591 is correct. > The inner workings of the chip are (see also datasheet): > > A read operation starts a new AD-conversion cycle, and returns the value from > the _last_ conversion. > Since there has been no conversion on a newly attached device, the first data > to be returned from a PCF8591 is always 0x80. The next read-operation will > return the result of the conversion triggered by the first read. > > Eberhard >
