Can't get 2 sensor chips working

David dpnsw at
Thu Feb 20 00:51:40 CET 2003


I am trying to get a PCF8591 and a PCF8574 working using the i2c-pport 

I have at the moment the i2c-pport and algo-bit modules loaded and am trying 
to get access to the PCF chips.

modprobe pcf8574
modprobe pcf8591
modprobe pcf8574 probe=0,0x20
modprobe pcf8591 probe=0,0x48

don't actually creaate any files under proc and the modules remain unused as 
far as lsmod is concerned.

I can get the devices up if I
modprobe pcf8574 force_pcf8574=0,0x20
modprobe pcf8591 force_pcf8591=0,0x48

everything loads, I get the relavent files under

it doesn't look like I am really taking to the chips though.

Changes I make on the inputs aren't reflected in the values under /proc.

If I run the i2cdetect 0 I get UU showing in both 0x20 and 0x48

I have used my scope and know that signals are getting to the chips in 
question but it isn't a storage scope so I can't look to see if the pulses 
are really valid i2c pulses.  

Any hints on what to do next.

Best Regards,

David Price

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