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6 years ago.
lpc1768 DAC behaviour during reset
With no load attached to the mbed DAC output the DAC output goes to around 2V while the reset button is held down. At power on the DAC output also goes high for a short bit of time. If i load the DAC with 1K i can reduce this effect to about 50mV.
How do i make sure the ouput stays at zero untill i tell it to go high in my code? Can i deal with this in software or do i have to clamp the output with a transistor and a RC time constant?
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While in reset that pin is a digital input with an internal pull up. It's going to go high, that is the power up default for the device.
posted by Andy A 06 Apr 2018more details and a solution on how to deal with this quirk here. https://electronics.stackexchange.com/questions/366392/dac-behaviour-on-reset-startup-lpc1768
and no it doesnt seem to boot as a regular input pin. Unloaded it doesnt go to 3.3V like it is supposed to if it were pulled up by internal pullups.
posted by Morten Herreborg 09 Apr 2018