All,
I have a mcp23008 that I am using with my rasberry pi. I am hooking it to 5v from the pi, and I am able to use i2c connect, and everything works great in that I am able to set a pin to on/off. However, when the chip is powered on, it's output pins are at 1.1v by default, even though the spec sheet says the gpio is set to all 0s. I suspect the chip is not hitting the POR values for some reason, but I have not been able to figure it out. I unplugged the i2c wires to make sure that was not a problem, as well. The reset is tied to 5v like in the tutorial, and I am using the gnd/power pins from the rasberry pi header port. Any ideas/suggestions on what I am doing wrong are appreciated!
Thank you!
MCP23008 power on reset and default values
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- adafruit_support_rick
- Posts: 35092
- Joined: Tue Mar 15, 2011 11:42 am
Re: MCP23008 power on reset and default values
1.1v is within the range of logic 0. However, you might try some pulldown resistors to get to a true 0v.
- uflynn
- Posts: 2
- Joined: Tue Apr 01, 2014 1:00 pm
Re: MCP23008 power on reset and default values
Rick,
Thank you for the suggestion on using pull-down resistors to make the voltage go to zero. I have found out with this device is that it's better to use it as a sink to ground, as it does not drive enough current to turn on a triac for my current application. Using it as a sink has worked great, and I don't worry that the device does not initialize the ports to 0 after being turned on.
Thank you for the suggestion on using pull-down resistors to make the voltage go to zero. I have found out with this device is that it's better to use it as a sink to ground, as it does not drive enough current to turn on a triac for my current application. Using it as a sink has worked great, and I don't worry that the device does not initialize the ports to 0 after being turned on.
Please be positive and constructive with your questions and comments.