Can't get 2 sensor chips working

Mark D. Studebaker mds at
Thu Feb 20 04:59:07 CET 2003

I've heard of other trouble with the parallel port adapters (i2c-pport and pcf-epp),
I don't know if it's the driver or the hardware that is the trouble.
I wouldn't want to debug it without a good 'scope.
Anything else is going to be quite frustrating.
Good luck.

David wrote:
> I don't know if I can do that without a storage CRO. I tried altering my 
> triggering but can't seem to hold the signal still long enough to actually 
> see it.
> Don't know if I can sample using my soundcard. I might be able to record 
> (dpending on whether the pport bus runs at less than 20Khz in speed.
> I then need to find an audio application that will display the waveform in 
> scope mode.
> Am I missing something or is this my next step?
> On Thursday 20 February 2003 12:14, Mark D. Studebaker wrote:
>>you can try i2cdump 0 0 0x20
>>then look on the scope.
>>If the chip is not responding you will see only the chip address and the
>>register address
>>(2 bytes for each access)
>>If the chip is responding you will see the 3rd byte on the bus (the chip
>>David wrote:
>>>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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