Please see https://blog.ipsumdomus.com/sonoff-switch-complete-hack-without-firmware-upgrade-1b2d6632c01 for a description on what the sonoff uses to cimmunicate with the chinese cloud.
On initial setup you just integrate the sonoff in your WLAN and then it communicates with the chinese cloud. The ewlink also communicates with the chinese cloud and status and other commands are stored and forwarded by the cloud to/from your sonoff device.
Hello
I already searched but was unable to find any Sound Pressure Level (SPL) metering project.
I am in the need to measure the SPL in dbA. It does not need to be that exact but should be that sensitive to see relative loudness changes.
Already tried some Arduino code that uses FFT to weight the level, but this is not very sensitive as the FFT is to slow. So the circuit should use a hardware A weighted filter.
I could create a circuit with a electret microphone, some opamp to amplifier the signal and an a-weighted frequency filter. And some other opamp and a capacitor to capture an analog voltage from that all. But I am looking for ready-to-use projects now.
Anyone already did this?
~Josef