I'm connecting a device into the mic input on an iPhone. The device puts out 1ms pulses a few times per second. My iPhone app then decodes these to display to the user. My circuit works however I'd like to understand exactly why.
The mic input has a 2.7VDC bias. I use the 47uF cap to decouple the VCC. The device output goes high for about 1ms a few times per second. So the cap lets the AC signal from my device through but blocks DC signals? What I'm confused about is how a signal gets generated that I can pick up on the iPhone when I'm adding 2.7V to the line that already has 2.7V.
The other thing that really has me confused is that I'm unable to see the output on my scope. No matter where I attach the probe I get no visible signal. However I see the pulses on the iPhone. This could be user error on my part on how to set the scope but I'm not sure.
Any help is appreciated.
The mic input has a 2.7VDC bias. I use the 47uF cap to decouple the VCC. The device output goes high for about 1ms a few times per second. So the cap lets the AC signal from my device through but blocks DC signals? What I'm confused about is how a signal gets generated that I can pick up on the iPhone when I'm adding 2.7V to the line that already has 2.7V.
The other thing that really has me confused is that I'm unable to see the output on my scope. No matter where I attach the probe I get no visible signal. However I see the pulses on the iPhone. This could be user error on my part on how to set the scope but I'm not sure.
Any help is appreciated.