topic Re: Analog On Digital Port in LPC Microcontrollers

Analog On Digital Port

mikenn — Wed, 03 Jan 2018 17:40:45 GMT

On LPC11E14 I use PIO0_12 and PIO0_14 as encoder inputs. As such these are both configured as digital inputs. I would like to add broken cable detection, which would involve placing an analog voltage (VCC/2) on PIO0_12 and PIO0_14. Then these pins would also connect to an analog input simultaneously. Are there any consequences to placing the VCC/2 level on the digitally configured inputs? Higher current drain perhaps? Latch up?

Re: Analog On Digital Port

soledad — Wed, 03 Jan 2018 22:53:52 GMT

Hi,

You only need to be careful with voltage and current maximum values. Regarding the voltage, if you configure the pin as a digital input, then this pin takes as logical “high” level a 0.7VDD voltage value and for “low” level 0.3VDD voltage value.

For example if VDD=3.3v the level high minimum is 2.31v, and the maximum “low” level is 0.99v, for 1.8v you are in the threshold voltage.

The max. current supported for digital pins is 10nA.

I hope this helps,

Have a great day,

Sol

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Re: Analog On Digital Port

mikenn — Wed, 03 Jan 2018 23:06:06 GMT

Whats up Soledad.

Just so I am clear, 10nA is the maximum input current on a digital input with input voltages of VCC, 0V, or VCC/2 ?

MikeN

Re: Analog On Digital Port

soledad — Thu, 04 Jan 2018 15:58:48 GMT

Hi,

Please check the following values from the datasheet.

I hope this helps,

Have a great day,
Sol

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