[HH] CO detectors self-destruct

[Greg London]

On Tue, April 18, 2017 11:27 am, Tom Metro wrote:
. The manufacturer wouldn't even
> splurge on a micro with an analog input,

Two gpio pins, a resistor, a capacitor,
and a digital counter can get you a cheap
approximation of an ADC in a digital only micro.

Put cap and resistors in series between ground and gpio.
Use gpio to discharge cap then pull it high.
Use another gpio as an input tied to the point between r and c.
Count how long it takes for gpio to go to 1.
A bit of calculation will tell you R of thing you measured.

I imagine a smoke co detector sample rate is extremely slow
And the accuracy is really just good/notgood
So it could work.