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aholcomb89 / WiFiLMR

Subscriber unit that communications via WiFi
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Audio Development Board #1

Open zjcers opened 5 years ago

zjcers commented 5 years ago

Digital inputs are not an option since no I2S input is exposed, analog audio looks like the best option at this point. The STM32 on the Photon can trigger both its ADCs and DACs from the timer modules, so this can be done with little software overhead (unlike other MCUs, like the TI Tiva, which can only sequence the ADCs from the timers).

The block diagram is on the Project Overview doc. Since I have a Wikipedia-level understanding of the circuitry involved, I think that these circuits should be designed separately from the rest, for now. They'll eventually make it back onto the main board, but for now this allows cheaper screw ups.

zjcers commented 4 years ago

Despite moving to a platform with I2S, I'm going to try the analog route at least for the output. The input side will likely be PDM since PDM mics are cheaper than the circuitry required to handle an analog mic. Also, the STM32L452 has a DFSDM block which implements a decimation filter in hardware, so we get PDM for basically free.