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aboudou
Posts: 98
Joined: Wed Aug 08, 2012 12:38 pm
Location: Cintegabelle, France
Contact: Website

I2C, MCP23008 and 0V on output

Thu Dec 27, 2012 9:52 am

Hi all,

I'm trying to use a MCP23008, but have an issue I don't understand :

- MCP23008 is powered on 3,3V line
- When not using it, voltage on SDA/SCL pins is at 3,3V
- When using it, voltage on SCL pin is at 2,5v and SDA pin is as 2V (same voltages if I power MCP23008 on the 5V line).
- When I set a pin to output, and HIGH value, voltage of the output pin is 0V instead of 3,3V
- Voltages on other pins (VDD and reset is at 3,3V)

What do you think the problem may be ? Issue with the RasPi ? Issue the MCP23008 ?

Thanks in advance for your help.
https://goddess-gate.com/ - My main website
http://raspberrypi.goddess-gate.com/ - A website about (and hosted by) my Raspberry Pi
https://twitter.com/boudouarnaud - Follow me on Twitter
http://www.fablab-sud31.fr/ - Fab Lab Sud31-Val d'Ariège

User avatar
aboudou
Posts: 98
Joined: Wed Aug 08, 2012 12:38 pm
Location: Cintegabelle, France
Contact: Website

Re: I2C, MCP23008 and 0V on output

Thu Dec 27, 2012 10:40 am

OK, I finally found the problem.

It was just an addresses issue with Adafruit_MCP230xx code : given register adresses are wrong for MCP23008. After the fix, all is working correctly.
https://goddess-gate.com/ - My main website
http://raspberrypi.goddess-gate.com/ - A website about (and hosted by) my Raspberry Pi
https://twitter.com/boudouarnaud - Follow me on Twitter
http://www.fablab-sud31.fr/ - Fab Lab Sud31-Val d'Ariège

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